American Journal of Epidemiology © The Author 2014. Published by Oxford University Press on behalf of the Johns Hopkins Bloomberg School of Public Health. All rights reserved. For permissions, please e-mail: [email protected]. Vol. 180, No. 11 DOI: 10.1093/aje/kwu254 Advance Access publication: October 4, 2014 Original Contribution Early-Life Predictors of Leisure-Time Physical Inactivity in Midadulthood: Findings From a Prospective British Birth Cohort Snehal M. Pinto Pereira, Leah Li, and Chris Power* * Correspondence to Prof. Chris Power, Population, Policy, and Practice, University College London, Institute of Child Health, 30 Guilford Street, London WC1N 1EH, United Kingdom (e-mail: [email protected]). Initially submitted July 2, 2014; accepted for publication August 26, 2014. Much adult physical inactivity research ignores early-life factors from which later influences may originate. In the 1958 British birth cohort (followed from 1958 to 2008), leisure-time inactivity, defined as activity frequency of less than once a week, was assessed at ages 33, 42, and 50 years (n = 12,776). Early-life factors (at ages 0–16 years) were categorized into 3 domains (i.e., physical, social, and behavioral). We assessed associations of adult inactivity 1) with factors within domains, 2) with the 3 domains combined, and 3) allowing for adult factors. At each age, approximately 32% of subjects were inactive. When domains were combined, factors associated with inactivity (e.g., at age 50 years) were prepubertal stature (5% lower odds per 1–standard deviation higher height), hand control/ coordination problems (14% higher odds per 1-point increase on a 4-point scale), cognition (10% lower odds per 1–standard deviation greater ability), parental divorce (21% higher odds), institutional care (29% higher odds), parental social class at child’s birth (9% higher odds per 1-point reduction on a 4-point scale), minimal parental education (13% higher odds), household amenities (2% higher odds per increase (representing poorer amenities) on a 19-point scale), inactivity (8% higher odds per 1-point reduction in activity on a 4-point scale), low sports aptitude (13% higher odds), and externalizing behaviors (i.e., conduct problems) (5% higher odds per 1–standard deviation higher score). Adjustment for adult covariates weakened associations slightly. Factors from early life were associated with adult leisure-time inactivity, allowing for early identification of groups vulnerable to inactivity. Britain; cohort study; leisure-time physical inactivity; life course even low activity levels (i.e., the avoidance of inactivity) protect against death (8, 9). Inactivity is a modifiable risk factor, and positive, sustainable behavior changes could lead to reduced health care costs and burden of disease. Inactivity prevention is, therefore, a key public health goal; understanding the determinants of inactivity in the general population at different life stages is required to develop interventions aimed at the prevention of inactivity-related chronic disease. It is possible that, within the broad range of macro- to individual-level influences on activity participation (10), earlylife factors might program later health and associated behaviors. Evidence that health behaviors tend to track from early life to adulthood (11) provides some support for a role of factors in early life. Potentially, such early influences on later inactivity could include physical, social, and behavioral domains (e.g., poor coordination (physical domain), adversities (social domain), and smoking (behavioral domain)). Previous work suggests that social and/or behavioral influences on adolescent Physical inactivity is highly prevalent with high avoidable health and economic costs. One-third of adults are estimated to be inactive (1), and worldwide inactivity is associated with approximately 5.3 million of 57 million deaths annually (2). For those who are inactive (defined as activity frequency of less than once per week), the risk of all-cause mortality was found to be higher compared with those who are highly active, with higher rates of cardiovascular death of 32% and 43% in men and women, respectively (3, 4). In developed countries, inactivity accounts for an estimated 1.5%–3.0% of total direct health care costs (5) (e.g., in 2006–2007, inactivity cost the United Kingdom’s National Health Service approximately £0.9 billion (6)). Given such health and economic costs, calls have been made for research on inactivity and its determinants (7), but the literature still focuses largely on higher activity levels. Although knowledge of influences on higher activity levels may be desirable, it is also important to understand the causes of inactivity, given evidence that 1098 Am J Epidemiol. 2014;180(11):1098–1108 Early-Life Predictors of Adult Leisure-Time Inactivity activity were stronger than physical influences (12, 13), but whether such effects are maintained into adulthood is unknown. Studies of adult (in)activity patterns have identified several contemporary influences, including physical factors (e.g., disabilities (14)), social factors (e.g., income (15)), and behavioral factors (e.g., smoking (16)). However, many studies of adults tend to be of mixed-aged, nonrepresentative samples (14–17), and importantly, most pay little attention to early-life factors that may represent the origins from which influences on later inactivity evolve. For example, adversities experienced in childhood could lead to poor emotional adjustment (18), which in turn can lead to the adoption of hazardous behaviors, such as inactivity. Using a nationwide general population sample, we aimed to identify influences on adult leisure-time inactivity. Our specific objectives were to examine associations with inactivity at ages 33, 42, and 50 years of 1) factors within each early-life domain (i.e., physical, social, and behavioral), separately and combined, 2) the 3 early-life domains combined, and 3) all domains allowing for adult factors. METHODS The 1958 British birth cohort is an ongoing longitudinal study of all persons born in Britain during 1 week in 1958 (n = 17,638) (19). Information was collected during childhood (at birth and at ages 7, 11, and 16 years) and adulthood (at ages 23, 33, 42, 45, and 50 years). Ethical approval was given by the London Multicentre Research Ethics Committee (London, United Kingdom); informed consent was obtained from participants at various ages (including at age 50 years). Respondents in midadulthood are broadly representative of the total surviving cohort (20). The sample for this study consists of cohort members with at least 1 measurement of inactivity (at age 33, 42, or 50 years), who were alive and living in Britain at age 50 years (n = 12,776). Physical inactivity at ages 33, 42, and 50 years was measured by asking participants about leisure-time activity frequency with a list of examples (e.g., swimming, going for walks). Similar to others (3, 4, 21), we identified low activity as an activity frequency of less than once per week, hereafter referred to as inactivity. Early-life predictors were identified from previous studies of adolescent activity (12, 13, 22–25) and adolescent predictors of adult (in)activity (26, 27). Most potential predictors were assessed prospectively from birth to age 16 years and categorized into 3 domains ( physical, social, and behavioral) (Table 1). Adult factors at age 33 years included social class (4 categories, as for parental social class at birth; see Table 1), education (5 categories ranging from none to university degree), measured body mass index (weight (kg)/height (m)2), number of children in the household (range, 0–8), physically limiting illness, and psychological items of the Malaise Inventory (28). To facilitate comparisons, we converted all continuous early-life factors (i.e., parental body mass index, maternal age, prepubertal stature, cognitive ability, internalizing behaviors (i.e., emotional problems), and externalizing behaviors (i.e., conduct problems or antisocial problems) to internally standardized z scores (mean = 0, standard deviation, 1). To estimate associations of early-life factors with adult inactivity, we conducted analyses in 3 steps. First, we examined associations of Am J Epidemiol. 2014;180(11):1098–1108 1099 factors within each domain (separately and then combined) with inactivity at ages 33, 42, and 50 years. We considered whether the within-person inactivity correlation at these 3 adult ages was an important analytical consideration by modeling the repeated binary outcome using generalized estimating equations, assuming an unstructured covariance matrix. To establish whether associations with early-life factors differed by age, we included an interaction term (age × factor). Estimated associations from models of generalized estimating equations were consistent with those from separate analyses of inactivity at ages 33, 42, and 50 years (Web Table 1, available at http://aje.oxfordjournals.org/). For ease of interpretation, all subsequent analyses were performed using separate analyses for inactivity at ages 33, 42, and 50 years. Hence, within each early-life domain, we examined univariate associations between each factor and inactivity at each age using separate logistic regression models. We then built 3 domain-specific multivariable models by including only factors specific to each domain. Second, we combined factors from the 3 domains in analyses of inactivity; any factor associated with inactivity (at age 33, 42, or 50 years) in domain-specific models was selected for inclusion in a model of the 3 domains combined. Third, we examined whether associations were independent of adult factors by adjusting for the adult factors described above. Differences in associations by sex between early-life factors and inactivity were examined using an interaction term (sex × factor). There was little evidence of effect modification; hence, data from both sexes were combined in analyses. Missing data ranged from 1% (on internalizing and externalizing behaviors) to 38% (on physical handicap/disabling condition). To minimize data loss, we imputed missing data by using multiple imputation chained equations; imputation models included all model variables, including previously identified key predictors of missingness (20). Regression analyses were run across 10 imputed data sets. Imputed results were broadly similar to those produced when using observed values; the former are presented. RESULTS At each adult age, approximately 32% of participants were inactive (Table 2); however, there was variation within persons as they aged. A total of 52% of the participants who were inactive at age 33 years were also inactive at age 42 years, and 48% of the participants who were inactive at age 42 years were also inactive at age 50 years (data not shown). Univariate and multivariable associations In initial analysis, we found no associations with inactivity at any of the 3 adult ages for low birth weight, birth order, paternal body mass index, pubertal timing, overweight or obesity, maternal employment, childhood abuse, or sleeping problems. Thereafter, these factors were excluded from analyses. Early-life physical factors. Most physical factors were related to inactivity at all 3 adult ages in univariate analyses. Associations were maintained in multivariable analyses, except for maternal smoking in pregnancy and physical handicap/disabling condition. Shorter prepubertal stature, poorer 1100 Pinto Pereira et al. Table 1. Potential Early-Life (Birth to Age 16 Years) Predictors of Adult Inactivity Among Participants in the 1958 British Birth Cohort, Followed From 1958 to 2008 Early-Life Factor Participant Age at Data Ascertainment, years Data Ascertainment Method Description Categories/Units Physical domain Low birth weight 0 Measured <2.5 kg Yes or no Maternal smoking during pregnancya 0 Parental report ≥1 Cigarette/day after fourth month of pregnancy Yes or no Maternal prepregnancy BMI 0 Parental report Weight (kg)/height (m)2 Continuous (z score) Age (in years) in 1958 Maternal age 0 Parental report Birth order 7 Parental report Continuous (z score) Prepubertal stature 7 Measured Height, measured using standardized protocolsb Paternal BMI 11 Parental report Weight (kg)/height (m)2 Continuous (z score) Pubertal timing 16 Medical examination For boys, rating of axillary hair stage Absent, sparse, intermediate, or adult ≤11, 12, 13, 14, or ≥15 Years Cognitive ability 16 Reading and mathematics tests (56) Derived age-standardized score for each test, converted to a scale of 0–100; average of the 2 tests was used (if missing, corresponding average from age 11 or 7 years was used). Continuous (z score) Physical handicap/ disabling condition 7, 16 Parental report Physical handicap/disabling condition at age 7 or 16 years Yes or no Overweight or obese 7, 11, 16 Measured International age-appropriate BMI cutoffs (57), summed across ages Number of ages (0, 1, 2, or 3) at which the participant was overweight or obese Hand control/ coordination 7, 11, 16 Teacher rating At each age, measured as no problems Number of ages (0, 1, 2, or 3) at (score = 0) versus somewhat or which the participant displayed such problems certainly applies (score = 1), summed across ages. Parental social class 0 Parental report Father’s occupational class at child’s birth (or if missing, at age 7 years), categorized according to the 1951 Registrar General’s Classification (59) 4 Categories (professional/ managerial, skilled nonmanual, skilled manual, or semiskilled/unskilled and single-parent households) Maternal employment 7 Parental report Full-time or part-time work since participant attended school Yes or no First, second to fourth, or fifth or higher For girls, age at menarche Continuous (z score) Social domain Parental divorce 33 Self-report Childhood abuse 45 Self-report Abuse (physical, psychological, or sexual) by age 16 years (58) Yes or no Yes or no Minimal parental education 0, 7 Parental report Both parents had minimal schooling Yes or no Childhood neglect 7, 11 Parental and teacher reports ≥2 of 5 Items at age 7 and/or 11 years Yes or no (teacher report of child’s physical appearance, parent report of involvement with child) Household amenities 7, 11, 16 Parental report Score of 0–18 (higher scores Availability of bathroom, indoor indicate more limited access) lavatory, and hot water; reported as sole use (score = 0), shared use (score = 1), or not available (score = 2); a composite score for all 3 ages was derived. Institutional care 7, 11, 16 Parental/guardian Ever in institutional care by age report 16 years Yes or no Table continues Am J Epidemiol. 2014;180(11):1098–1108 Early-Life Predictors of Adult Leisure-Time Inactivity 1101 Table 1. Continued Early-Life Factor Participant Age at Data Ascertainment, years Data Ascertainment Method Description Categories/Units Behavioral domain Participants were asked how often they Most active, very active, active, or least active played 1) outdoor and 2) indoor games and sports; 3) went swimming; and 4) went dancing. Responses were often (score = 2), sometimes (score = 1), or never (score = 0). Scores were summed across the 4 variables and collapsed to 4 categories (55). Physical activity level 16 Self-report Average or below average sports aptitude 16 Self-report Yes or no Dissatisfaction with nearby sporting facilities 16 Self-report Yes or no Internalizing behaviors (emotional problems) 16 Teacher rating Using 5 items from the 26-item Rutter Continuous (z score) Behavior Scale, categorized as applies (score = 2), somewhat applies (score = 1), or does not apply (score = 0); scores were summed across the 5 items (if missing, measurements from age 11 or 7 years were used) (54). Externalizing behaviors (conduct problems) 16 Teacher rating Using 9 items from the Rutter Behavior Continuous (z score) Scale; scores were summed (if missing, measurements from age 11 or 7 years were used) (54). Sociability 16 Teacher rating 5 Categories (sociable to withdrawn) Smoking 16 Self-report Yes or no Alcohol consumption in last week 16 Self-report Sleeping problems 16 Parental report ≥7 Units, 3–6 units, 0–2 units, or Number and type of drinks (pints of never drinkers beer, glasses of wine, or measures of spirits) consumed in the past week; amount of alcohol was coded into standard units and categorized into 4 groups (53). None, mild, or severe Abbreviation: BMI, body mass index. a Maternal smoking in pregnancy was included as a physical factor because of its association with offspring’s physical characteristics (such as neurological deficits) (60). b Height was measured with no shoes to the nearest centimeter, half-inch, or inch (1 inch = 2.54 cm), converted to meters, and standardized. cognition, and poor hand control/coordination were related to inactivity, with similar magnitudes of association at ages 33, 42, and 50 years (Table 3). Early-life social factors. Most social factors were related to inactivity at all 3 adult ages in univariate analyses. Associations were maintained in multivariable analyses, except for parental divorce, poor household amenities, and institutional care at some, though not all, ages. Lower parental social class at child’s birth, minimal parental education, and childhood neglect were associated with higher odds of inactivity at ages 33, 42, and 50 years (Table 3). Early-life behavioral factors. In univariate analyses, most behavioral factors were related to inactivity at all 3 adult ages. Associations were maintained in multivariable analyses except for dissatisfaction with nearby sporting facilities, and at some ages, internalizing behavior, unsociability, and lower Am J Epidemiol. 2014;180(11):1098–1108 alcohol consumption. Lower activity levels, average or below average sports aptitude, externalizing behavior, and smoking were related to inactivity at ages 33, 42, and 50 years, with varying magnitudes of association (Table 3). Associations for combined domains and with adjustment for adult factors In models that adjusted for factors from all domains simultaneously (Table 4), the odds ratios for inactivity at age 33 years ranged from 0.86 (95% confidence interval: 0.82, 0.91) for 1–standard deviation higher cognition to 1.41 (95% confidence interval: 1.23, 1.61) for average or below average sports aptitude. Lower activity levels, average or below average sports aptitude, and poorer cognition were related to inactivity at all 3 adult ages. Associations with 1102 Pinto Pereira et al. Table 2. Characteristics of Participants in the 1958 British Birth Cohort Study, Followed From 1958 to 2008a Characteristic No. % Mean (SD) Physical inactivityb At age 33 years 3,426 31.30 At age 42 years 3,822 34.42 At age 50 years 2,955 30.38 Physical Domain Prepubertal stature (at age 7 years), cm Physical handicap/disabling condition at age 7 or 16 years 122.41 (5.90) 934 11.75 No. of ages at which hand control/coordination problems were present (assessed at ages 7, 11, and 16 years) 0 4,077 56.81 1 1,970 27.45 2 841 11.72 3 288 4.01 Social Domain Parental social class at child’s birth Professional/managerial 2,210 17.87 Skilled nonmanual 1,206 6,053 48.93 Semiskilled, unskilled, or single-parent household 2,901 23.45 Minimal parental educationc 6,609 60.32 Childhood neglectc 2,249 19.05 Parental divorce 1,673 15.38 Institutional care (at ages 7, 11, or 16 years)c 495 DISCUSSION 9.75 Skilled manual 6.38 Household amenities scorec 1.10 (2.71) Behavioral Domain Physical activity level at age 16 years Low 4,475 46.84 Active 1,844 19.30 Very 1,405 14.71 Most Average or below average sports aptitude at age 16 yearsc 1,830 19.15 7,004 73.89 Sociability at age 16 yearsc 1 (Sociable) 2,279 23.33 2 3,313 33.91 3 2,664 27.27 4 1,356 13.88 5 (Withdrawn) 158 cognition were similar at all ages, whereas the associations for lower activity levels, average or below average sports aptitude, and smoking attenuated with age (e.g., the odds ratio for smoking was 1.23 (95% confidence interval: 1.10, 1.38) at age 33 years but nonsignificant at age 50 years). Shorter prepubertal stature, poor hand control/coordination, lower parental social class at child’s birth, minimal parental education, parental divorce, poorer household amenities, institutional care, externalizing behavior, and unsociable behaviors were related to inactivity at ages 42 and/or 50 years but not at age 33 years. Maternal body mass index and age, childhood neglect, internalizing behaviors, and alcohol consumption were not associated with adult inactivity when domains were analyzed simultaneously. After adjustment for adult covariates, parental education and household amenities were no longer associated with adult inactivity (Table 5). For poorer cognition, smoking, and average or below average sports aptitude, associations were seen at age 33 years and/or 42 years but not at age 50 years; whereas for shorter prepubertal stature, poor hand control/coordination, lower parental social class at child’s birth, parental divorce, institutional care, and externalizing and unsociable behaviors, associations remained, although slightly attenuated, at ages 42 and/or 50 years but not at 33 years. Associations between activity level at age 16 years and inactivity at all 3 adult ages were maintained. 1.62 Abbreviation: SD, standard deviation. a Numbers vary because of missing data. b Leisure-time physical activity of less than once per week. c See Table 1 for a description of this factor. In a nationwide general population sample followed from birth, we identified 3 important findings. First, approximately one-third of the population was inactive during leisure time in adulthood, and the prevalence of inactivity was similar across 3 ages (i.e., 33, 42, and 50 years). Low activity levels during adolescence were associated with inactivity decades later in adulthood, suggesting that inactivity tracks over long periods of life. Second, by examining an extensive array of early-life factors, we showed that factors from childhood, spanning exposures and developmental markers (e.g., shorter prepubertal stature, low parental social class, and externalizing behavior) were related to adult inactivity. Associations ranged from 14% lower odds of inactivity for 1–standard deviation higher cognition to 41% higher odds of inactivity for average or below average sports aptitude. Third, our findings suggest that pathways through which early-life factors influence adult inactivity vary. For example, adolescent cognition may operate partly through subsequent adult characteristics, whereas prepubertal stature may influence inactivity independently of other early-life or adult factors, possibly indicating “programming” of adult behaviors. A strength of this study is the repeat, identical measurements that allowed comparison of inactivity over a substantial period in adulthood. The data enabled examination of a wide range of prospectively measured predictors from different early-life domains. To our knowledge, no other study has investigated such an extensive array of early-life factors simultaneously. We were also able to examine whether early-life factors were associated with adult inactivity independent of adult factors. However, the study has limitations. Our activity Am J Epidemiol. 2014;180(11):1098–1108 Am J Epidemiol. 2014;180(11):1098–1108 Table 3. Odds Ratios of Physical Inactivity at 3 Adult Ages for Early-Life Factors in 3 Domains, Estimated From Domain-Specific Univariate and Multivariable Modelsa in the 1958 British Birth Cohort, Followed From 1958 to 2008 Univariate Models Early-Life Factor Age 33 Years OR 95% CI Age 42 Years OR 95% CI Multivariable Models Age 50 Years OR 95% CI Age 33 Years OR 95% CI Age 42 Years OR Age 50 Years 95% CI OR 95% CI Physical Domain Prepubertal statureb 0.90 0.86, 0.94 0.89 0.85, 0.93 0.89 0.85, 0.93 0.94 0.90, 0.99 0.93 0.89, 0.98 0.93 0.89, 0.98 Hand control/coordination problemsc,d 1.20 1.14, 1.27 1.20 1.13, 1.28 1.28 1.21, 1.36 1.12 1.05, 1.20 1.11 1.05, 1.17 1.19 1.11, 1.27 Cognition at age 16 yearsb,d 0.80 0.77, 0.83 0.79 0.76, 0.82 0.77 0.74, 0.81 0.84 0.81, 0.88 0.84 0.80, 0.87 0.83 0.79, 0.88 d,e Physical handicap/disabling condition 1.18 0.997, 1.40 1.28 1.10, 1.49 1.18 1.002, 1.38 1.02 0.84, 1.24 1.11 0.96, 1.28 0.98 0.83, 1.15 Maternal smoking in pregnancyd,e 1.16 1.06, 1.28 1.12 1.03, 1.22 1.12 1.02, 1.23 1.09 0.99, 1.20 1.05 0.96, 1.14 1.05 0.95, 1.15 Maternal BMI in 1958b,f 1.04 0.99, 1.08 1.05 1.01, 1.10 1.06 1.02, 1.11 1.03 0.99, 1.08 1.05 1.01, 1.10 1.06 1.01, 1.11 Maternal age at child’s birthb 0.98 0.94, 1.02 0.95 0.92, 0.99 0.97 0.93, 1.01 0.99 0.94, 1.03 0.96 0.92, 0.997 0.97 0.93, 1.02 Parental social class at child’s birthc,d,g 1.12 1.07, 1.16 1.16 1.11, 1.20 1.23 1.17, 1.29 1.06 1.01, 1.11 1.10 1.05, 1.15 1.13 1.07, 1.19 Minimal parental educationd,e 1.26 1.15, 1.37 1.28 1.18, 1.38 1.42 1.29, 1.57 1.14 1.04, 1.26 1.13 1.03, 1.24 1.22 1.10, 1.35 Childhood neglectd,e 1.32 1.16, 1.50 1.33 1.20, 1.49 1.43 1.28, 1.60 1.20 1.04, 1.38 1.21 1.08, 1.36 1.21 1.08, 1.35 Parental divorce 1.17 1.04, 1.32 1.11 0.99, 1.25 1.34 1.18, 1.51 1.12 0.99, 1.27 1.06 0.94, 1.20 1.25 1.10, 1.41 Institutional cared,e 1.24 1.02, 1.52 1.14 0.91, 1.41 1.73 1.43, 2.08 1.10 0.90, 1.35 1.00 0.80, 1.25 1.44 1.19, 1.74 Household amenitiesc,d 1.03 1.01, 1.04 1.03 1.01, 1.04 1.04 1.03, 1.05 1.02 1.001, 1.03 1.01 0.999, 1.03 1.02 1.01, 1.04 Social Domain e Activity level at age 16 yearsc,d,h 1.20 1.15, 1.26 1.19 1.13, 1.24 1.11 1.06, 1.15 1.14 1.08, 1.20 1.15 1.10, 1.21 1.08 1.04, 1.13 Average or below average sports aptitude at age 16 yearsd,e 1.64 1.45, 1.86 1.39 1.24, 1.56 1.28 1.15, 1.43 1.41 1.23, 1.62 1.20 1.06, 1.35 1.17 1.04, 1.32 Dissatisfaction with nearby sporting facilities at age 16 yearsd,e 1.15 1.05, 1.26 1.12 1.01, 1.24 1.00 0.89, 1.12 1.08 0.98, 1.19 1.06 0.96, 1.17 0.96 0.85, 1.08 Internalizing behavior at age 16 yearsb,d 1.14 1.10, 1.19 1.13 1.09, 1.18 1.15 1.10, 1.20 1.07 1.03, 1.12 1.04 0.99, 1.09 1.07 1.03, 1.12 Externalizing behavior at age 16 years 1.09 1.04, 1.14 1.16 1.12, 1.21 1.17 1.12, 1.21 1.05 1.01, 1.10 1.12 1.07, 1.18 1.13 1.08, 1.18 Sociability at age 16 yearsc,i 1.11 1.06, 1.16 1.15 1.10, 1.20 1.11 1.06, 1.17 1.03 0.98, 1.08 1.07 1.02, 1.13 1.04 0.98, 1.10 Smoking at age 16 yearse 1.28 1.15, 1.44 1.34 1.21, 1.49 1.25 1.10, 1.41 1.31 1.17, 1.46 1.28 1.14, 1.45 1.18 1.04, 1.34 Alcohol consumption in last week at age 16 yearsc,d,j 1.08 1.02, 1.13 1.02 0.98, 1.06 1.02 0.96, 1.09 1.08 1.02, 1.14 1.03 0.98, 1.08 1.03 0.97, 1.10 b,d 1103 Abbreviations: BMI, body mass index; CI, confidence interval; OR, odds ratio. a Analysis adjusted for sex. Initial analysis found no associations with inactivity at ages 33, 42, and 50 years for several factors (birth weight, birth order, paternal BMI, pubertal timing, overweight or obesity, maternal employment, childhood abuse, and sleeping problems). b Per 1–standard deviation increase. c Per increase in scale. d See Table 1 for a description of this factor. e Those with versus those without the attribute. f BMI is weight (kg)/height (m)2. g Measured on a scale ranging from high (professional/managerial) to low (semiskilled/unskilled or single-parent household). h Measured on a scale ranging from most active to least active. i Based on teacher ratings on a scale ranging from sociable to withdrawn. j Measured on a scale ranging from 7 or more units/week to never drinkers. Early-Life Predictors of Adult Leisure-Time Inactivity Behavioral Domain 1104 Pinto Pereira et al. Table 4. Odds Ratio of Physical Inactivity at 3 Adult Ages for Early-Life Factors in All Domains (Physical, Social, and Behavioral) Combined, Estimated From Multivariable Models in the 1958 British Birth Cohort, Followed From 1958 to 2008a Age at Which Participants Were Inactive Early-Life Factor 33 Years OR 95% CI 42 Years OR 95% CI 50 Years OR 95% CI Physical Domain Prepubertal statureb 0.96 0.91, 1.00 0.94 0.90, 0.99 0.95 0.90, 0.996 Hand control/coordination problemsc,d 1.05 0.98, 1.12 1.06 0.99, 1.12 1.14 1.06, 1.23 Cognition at age 16 yearsb,d 0.86 0.82, 0.91 0.87 0.83, 0.92 0.90 0.85, 0.95 Maternal BMI in 1958b,e 1.02 0.97, 1.07 1.04 0.99993, 1.09 1.05 0.997, 1.10 Maternal age at child’s birthb 0.99 0.95, 1.04 0.96 0.92, 1.01 1.00 0.95, 1.04 Social Domain Parental social class at child’s birthc,d,f 1.01 0.97, 1.06 1.05 1.002, 1.10 1.09 1.03, 1.15 Minimal parental educationd,g 1.05 0.95, 1.16 1.03 0.94, 1.13 1.13 1.01, 1.25 Childhood neglectd,g 1.03 0.89, 1.19 1.02 0.89, 1.16 1.03 0.91, 1.16 Parental divorce 1.08 0.95, 1.24 0.99 0.88, 1.13 1.21 1.07, 1.37 Institutional cared,g 0.99 0.80, 1.22 0.87 0.69, 1.10 1.29 1.06, 1.57 Household amenitiesc,d 1.01 0.995, 1.03 1.01 0.99, 1.02 1.02 1.002, 1.03 g Behavioral Domain c,d,h Activity level at age 16 years 1.15 1.09, 1.21 1.16 1.11, 1.22 1.08 1.04, 1.13 Average or below average sports aptitude at age 16 yearsd,g 1.41 1.23, 1.61 1.19 1.05, 1.34 1.13 1.01, 1.28 Internalizing behavior at age 16 yearsb,d 1.03 0.99, 1.08 1.00 0.95, 1.05 1.02 0.97, 1.06 Externalizing behavior at age 16 years 1.00 0.96, 1.06 1.07 1.02, 1.13 1.05 1.01, 1.10 Sociability at age 16 yearsc,i 1.02 0.97, 1.07 1.07 1.02, 1.12 1.03 0.97, 1.08 Smoking at age 16 yearsg 1.23 1.10, 1.38 1.21 1.06, 1.37 1.10 0.97, 1.25 Alcohol consumption in last week at age 16 yearsc,d,j 1.05 0.99, 1.11 0.99 0.94, 1.05 0.99 0.93, 1.05 b,d Abbreviations: BMI, body mass index; CI, confidence interval; OR, odds ratio. a Analysis adjusted for sex and all factors in the table. b Per 1–standard deviation increase. c Per increase in scale. d See Table 1 for a description of this factor. e BMI is weight (kg)/height (m)2. f Measured on a scale ranging from high (professional/managerial) to low (semiskilled/unskilled or single-parent household). g Those with versus those without the attribute. h Measured on a scale ranging from most active to least active. i Based on teacher ratings on a scale ranging from sociable to withdrawn. j Measured on a scale ranging from 7 or more units/week to never drinkers. measures are limited to leisure-time activity, rather than total activity, which would include other domains (e.g., occupation). There is no consistent definition of inactivity that we could apply here; some studies use failure to meet recommended activity levels (2, 16), whereas others identify the least active persons in a population (26, 27, 29). Our measure is based on self-reported infrequent activity (<1 time/week), which has been used previously (3, 4, 21) and found to be associated with mortality risk (3, 4). Organization of earlylife factors into 3 domains was subjective, but it afforded a structured and pragmatic approach; moreover, the domains are related to theoretical constructs of health and social capital (30). Because the study is observational, uncontrolled covariates could account for some of the observed associations. Finally, as with any long-term study, sample attrition occurred over follow-up, although respondents in midadulthood were broadly representative of the surviving cohort (20). Maximizing available data, our models included participants with at least 1 measurement of inactivity at age 33, 42, or 50 years, who were living in Britain at age 50 years. We avoided sample reductions due to missing information by using multiple imputation (31). Despite calls for better understanding of inactivity (7), most research focuses on higher levels of activity or sedentary Am J Epidemiol. 2014;180(11):1098–1108 Early-Life Predictors of Adult Leisure-Time Inactivity 1105 Table 5. Odds Ratios of Physical Inactivity at 3 Adult Ages for Early-Life Factors in All Domains (Physical, Social, and Behavioral) Combined, Estimated From Multivariable Models, With Adjustment for Adult Factorsa in the 1958 British Birth Cohort, Followed From 1958 to 2008 Age at Which Participants Were Inactive Early-Life Factor 33 Years OR 95% CI 42 Years OR 95% CI 50 Years OR 95% CI Physical Domain Prepubertal statureb 0.96 0.91, 1.01 0.94 0.90, 0.99 0.94 0.89, 0.99 Hand control/coordination problemsc,d 1.03 0.96, 1.10 1.03 0.97, 1.11 1.09 1.01, 1.18 Cognition at age 16 yearsb,d 0.95 0.90, 1.01 0.94 0.88, 0.999 1.01 0.94, 1.08 Maternal BMI in 1958b,e 1.01 0.96, 1.06 1.03 0.99, 1.08 1.02 0.97, 1.07 Maternal age at child’s birthb 1.00 0.95, 1.04 0.96 0.92, 1.01 1.00 0.95, 1.05 Social Domain Parental social class at child’s birthc,d,f 1.00 0.95, 1.05 1.04 0.99, 1.09 1.07 1.01, 1.13 Minimal parental educationd,g 1.02 0.92, 1.13 1.00 0.91, 1.10 1.07 0.96, 1.19 Childhood neglectd,g 0.99 0.85, 1.14 0.99 0.87, 1.13 0.99 0.88, 1.12 Parental divorce 1.04 0.91, 1.19 0.97 0.85, 1.10 1.19 1.04, 1.35 Institutional cared,g 0.96 0.78, 1.19 0.86 0.68, 1.08 1.30 1.07, 1.59 Household amenitiesc,d 1.01 0.99, 1.02 1.01 0.99, 1.02 1.01 0.999, 1.03 g Behavioral Domain c,d,h Activity level at age 16 years 1.15 1.09, 1.21 1.16 1.11, 1.21 1.09 1.04, 1.14 Average or below average sports aptitude at age 16 yearsd,g 1.41 1.23, 1.62 1.18 1.05, 1.33 1.11 0.98, 1.26 Internalizing behavior at age 16 yearsb,d 1.03 0.99, 1.07 0.99 0.95, 1.05 1.01 0.97, 1.06 Externalizing behavior at age 16 years 0.98 0.93, 1.03 1.06 1.01, 1.11 1.03 0.99, 1.09 Sociability at age 16 yearsc,i 1.02 0.97, 1.07 1.06 1.01, 1.12 1.02 0.97, 1.08 Smoking at age 16 yearsg 1.18 1.06, 1.32 1.17 1.03, 1.33 1.06 0.94, 1.20 Alcohol consumption in last week at age 16 yearsc,d,j 1.05 0.995, 1.12 1.00 0.95, 1.05 1.00 0.93, 1.06 b,d Abbreviations: BMI, body mass index; CI, confidence interval; OR, odds ratio. a All models were adjusted for sex, all factors in the table, and the following variables assessed at age 33 years: educational level, BMI, number of children in the household, mental health, physically limiting illness, and social class. b Per 1–standard deviation increase. c Per increase in scale. d See Table 1 for a description of this factor. e BMI is weight (kg)/height (m)2. f Measured on a scale ranging from high (professional/managerial) to low (semiskilled/unskilled or single-parent household). g Those with versus those without the attribute. h Measured on a scale ranging from most active to least active. i Based on teacher ratings on a scale ranging from sociable to withdrawn. j Measured on a scale ranging from 7 or more units/week to never drinkers. behavior. However, sedentary behavior and physical (in)activity may represent separate constructs, contributing to disease risk via independent pathways (32). The various definitions of inactivity make comparison with other studies difficult, but some consistent themes can be identified. As expected, we found that lower activity levels and average or below average sports aptitude at age 16 years were associated with higher odds of inactivity in adulthood, which agrees with the results of other studies of (in)activity from adolescence to adulthood (33, 34). Moreover, the attenuating association with age, from 52% higher odds at age 33 years (most vs. least active at age 16 Am J Epidemiol. 2014;180(11):1098–1108 years) to 26% higher odds at age 50 years, is consistent with observations that tracking is stronger over short periods and attenuates through the life course (7). Even so, continuities in inactivity over long periods suggest that efforts to reduce childhood inactivity may have benefits in later life. The particularly novel finding of our study is that many factors across early-life domains were related to adult inactivity. Because most previous studies addressed adult rather than early-life predictors (14–17), they cannot shed light on how influences on adult inactivity have evolved. In some instances, our results underline the early-life or developmental 1106 Pinto Pereira et al. origins of particular predictors of adult inactivity. For example, educational attainment, which largely reflects cognitive development across earlier life (i.e., before adulthood) has been associated with adult activity (15, 16, 26, 27, 29); whereas our study highlights earlier abilities specifically, with approximately 12% lower odds of adult inactivity per 1–standard deviation higher cognition. Such findings, in agreement with those from a Finnish birth cohort (27), imply that early cognitive ability has a long-term influence on adult behavior, partly because it influences educational level and related social destinations in adulthood. However, in addition to operating in part via adult characteristics, this long-term association for cognition and other findings from our study may point to “programming” of behaviors such as inactivity (an idea raised by others (12)) or at least early-life vulnerabilities. Notably, in this regard, we found shorter prepubertal stature to be related to adult inactivity. Shorter stature in childhood and adulthood is associated with adult morbidity and mortality risk (35), but to our knowledge, there is only 1 previous study linking short stature with subsequent activity levels (23). Thus, our finding is novel: a 1–standard deviation increase in height (6.5 cm) at age 7 years was related to 6% lower odds of inactivity at age 50 years, independent of other early-life and adult factors. This finding may reflect growth tempo, yet no association was seen for pubertal timing, and maturation status has been shown to have inconsistent associations with adolescent activity (22). It is possible that this is a chance finding, although associations seen for other early-life physical factors suggest that some developmental markers may affect later risk of inactivity. Specifically, hand control/coordination problems at age 7, 11, or 16 years were associated with 14% higher odds of inactivity at age 50 years, whereas problems identified at all 3 ages in childhood were associated with 48% higher odds of inactivity at age 50 years. This finding is consistent with reported associations between fewer health problems in childhood and higher odds of being a very active adult (26). Interestingly, shorter prepubertal stature and poor hand control/coordination were related to inactivity at later ages (42 and 50 years) but not at an earlier age (33 years). A possible explanation could be that prepubertal stature and hand control/coordination problems augur earlier onset of poor health in adulthood. We explored this possibility in analyses of inactivity at age 50 years by including additional adjustment for biomarkers at age 45 years (i.e., lung function, blood pressure, lipids, and glycated hemoglobin) and self-reported poor health at age 50 years, and we found that associations were little affected (data not shown). Thus, our findings for prepubertal stature and hand control/coordination problems are consistent with early programming of adult inactivity. There are several processes that may be operating. There may be a lack of suitable activity options in childhood for those with poor hand control/coordination or short stature; were these options available, they might subsequently mitigate against leisure-time inactivity in adulthood. Alternatively, there may be neurological deficits in these groups (36) that impede activity participation, as suggested by our finding that poorer early cognitive ability predicts adult inactivity. Further investigation of the possible processes involved is warranted. However, if early programming of adult inactivity is operating, it did not appear to extend to other early factors. Specifically, we found no association for low birth weight or birth order, which agrees with results of studies of adolescent activity (37) though not for birth order (12, 13). Whereas others have reported that adiposity predicts subsequent lower activity levels (38–40) and sedentary behavior (41), we, like others (12), found no such association. Discrepancies could be caused by differences in definitions of inactivity or age of outcome with studies examining children (38, 40) or mixed-age adult samples (39), even though the adiposity– physical inactivity association could change with age (42). Externalizing and unsociable behaviors in adolescence were related to inactivity at age 42 years and/or 50 years, but not at age 33 years. Corresponding findings for greater adolescent sociability and higher levels of activity in adolescence (24) and adulthood (26) have been observed, and 1 review identified extraversion (of which sociability is a component) as a correlate of activity (43). However, internalizing behavior in adolescence was shown here to be unrelated to inactivity in adulthood after allowance for physical and social factors. Smoking in adolescence has been shown to predict lower activity levels in white adolescents (25), and here we found an association with later inactivity that attenuates with age from 33, to 42, to 50 years. It is possible that, because risk behaviors such as inactivity and smoking tend to cooccur (44), the association for adolescent smoking reflects or anticipates future cooccurring behaviors. Several social factors (i.e., low parental social class, minimal parental education, parental divorce, poor household amenities, and institutional care) were related to inactivity later in adulthood, but not at age 33 years. As would be expected for such “downstream” influences, associations appear to operate mostly via early-life physical and behavioral development, as suggested by a comparison of Tables 3 and 4. We might also expect that associations for early-life factors operate via adult factors, given associations of low adult social class with inactivity in cross-sectional studies (45, 46). Yet upon adjustment, attenuation of associations for social factors was modest, suggesting that their influence is independent of adult factors. Per 1-point lower parental social class at child’s birth (on a 4-point scale), the odds of inactivity at age 50 years were higher by 9% (i.e., those from unskilled manual backgrounds had 30% higher odds of inactivity at age 50 years compared with those from professional/managerial backgrounds). These associations may be caused by poorer adult health of those from unskilled manual groups, as previously documented (e.g., low childhood social class was related to chronic widespread pain in midadulthood, independently of adult social position (47)). In turn, chronic widespread pain may lead to inactivity. Yet, associations for inactivity at age 50 years were little affected by additional adjustment for adult biomarkers and poor health (data not shown). Alternatively, a manual occupation may not be conducive to physical activity during leisure time among parents (48), with transmission of behavior to offspring (i.e., children were more active if their parents were active early in the children’s lives (13)). Intergenerational transfer of behaviors is known to occur, with specific parental health-risk behaviors (e.g., not exercising) predicting similar behavior in their children (49) and, with tracking, inactivity could continue into adulthood. Adult leisure-time inactivity appears to be influenced by a range of factors over the formative early-life period and not Am J Epidemiol. 2014;180(11):1098–1108 Early-Life Predictors of Adult Leisure-Time Inactivity solely in adulthood. Our study highlights specific early-life capabilities, attributes, and environments that were associated with adult inactivity. These findings suggest potential pathways through which early-life factors could influence different aspects of adult health. For example, prepubertal stature, poor physical control/coordination in childhood, and low social class all have well-known associations with adult outcomes such as obesity, cardiovascular risk, and death (30, 35, 36). Our results suggest that adult inactivity could be on the pathway between these early-life factors and adult outcomes, whereas null findings for low birth weight suggest that adult inactivity is less likely to be on the pathway to adult health outcomes. Although we acknowledge broader macro-level influences on inactivity (10, 50), our findings imply the existence of groups who are vulnerable in early life for whom intervention is needed to avoid future leisure-time inactivity in adulthood. Health 2020, the World Health Organization’s European health policy framework, indicates that social gradients of health are a key challenge; the World Health Organization’s website has identified the importance of promoting activity in socially disadvantaged groups (51). These policies and our findings, taken together, raise the question of whether there might be strategies or interventions to broaden activity participation to such groups (e.g., those with shorter prepubertal stature, lower social class, or unsociable behaviors) who might otherwise become inactive adults. For example, strategies could include broadening the range of activities available. More generally, our findings support arguments for early-life investments to maximize health and social capital for long-term health gains (52). ACKNOWLEDGMENTS Author affiliations: Population, Policy, and Practice, Institute of Child Health, University College London, London, United Kingdom (Snehal M. Pinto Pereira, Leah Li, Chris Power). This work was supported by the Department of Health Policy Research Programme through the Public Health Research Consortium (PHRC). The views expressed in the publication are those of the authors and not necessarily those of the Department of Health. Information about the wider program of the PHRC is available at http://phrc.lshtm.ac.uk. The Great Ormond Street Hospital/University College London Institute of Child Health was supported in part by the Department of Health’s National Institute for Health Research Biomedical Research Centre. The funders had no input into the study design; data collection, analysis, and interpretation; the writing of the report; or the decision to submit the article for publication. Researchers were independent of influence from study funders. Conflict of interest: none declared. REFERENCES 1. Hallal PC, Andersen LB, Bull FC, et al. Global physical activity levels: surveillance progress, pitfalls, and prospects. 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