Vol. 25, No. 1
Printed In Great Britain
International Journal of Epidemiology
O International EpWemtotoglcal Association 1996
Conditioning Leisure Time Physical
Activity and Cardiorespiratory Fitness
in Sociodemographic Groups of
Middle-Aged Men in Eastern Finland
TIMO A LAKKA, JUSSI KAUHANEN AND JUKKA T SALONEN
Lakka T A (Research Institute of Public Health, University of Kuopio, PO Box 1627, 70211 Kuopio, Finland), Kauhanen
J and Salonen J T. Conditioning leisure time physical activity and cardiorespiratory fitness in sociodemographic groups
of middle-age men In Eastern Finland. International Journal of Epidemiology 1996; 25: 86-93.
Background. Physical inactivity and poor cardiorespiratory fitness have been found to be associated with an increased
risk of coronary heart disease, hypertension, stroke, non-lnsulin-dependent diabetes mellitus and cancer.
Methods. To characterize the least active and the least fit sociodemographic groups of middle-aged males, we Investigated conditioning leisure time physical activity and maximal oxygen uptake (VO2max) in a population sample of
2589 men aged 42-60 years In Eastern Finland.
Results. In covariate models, younger (P= 0.004), rural ( P < 0.001), married or engaged (P=0.04), lower Income
(P = 0.009), and employed men (P < 0.001), as well as fanners (P < 0.001) had a shorter duration of physical activity,
whereas older ( P < 0.001), urban (P = 0.05), single ( P < 0.001), less educated ( P < 0.001), lower income ( P < 0.001),
and unemployed or retired men (P < 0.001), as well as blue-collar workers (P < 0.001) had a lower mean intensity of
physical activity than others. Older ( P < 0.001), single ( P < 0.001), less educated ( P < 0.001), lower income ( P < 0.001),
and unemployed or retired men (P < 0.001), as well as blue-collar workers and farmers (P < 0.001) had lower VO2max
than others.
Conclusion. On the basis of our data, for health promotion regarding physical activity, special attention should be paid to
people in a lower sodoeconomic position.
Keywords: exercise, physical fitness, age, residence, marital status, socloeconomic status, educational status,
occupations, employment
activity and to improve cardiorespiratory fitness of the
least active and the least fit.
Previous population studies suggest that older,4'24"27
less educated,24"26 and lower income people,24"26 a$
well as those undertaking strenuous work, such as bluecollar workers, 24 ' 28 take less physical activity at their
leisure time than others. However, there are few population-based data on leisure time physical activity according to place of residence24-29 and marital status.26-27
Furthermore, little is known about the duration and
intensity of leisure time physical activity and the level
of cardiorespiratory fitness in different sociodemographic groups.
We investigated both the duration and mean intensity of conditioning leisure time physical activity and
V0 2 max in various sociodemographic groups of middleaged men in Eastern Finland. The main purpose of this
paper is to characterize those who have the lowest
level of conditioning leisure time physical activity and
V0 2 max and who therefore could be at increased risk of
chronic diseases.
Physical inactivity at leisure time and poor cardiorespiratory fitness have been found to be related to an
increased risk of coronary heart disease (CHD),1"10
hypertension,"' 12 stroke, 13 ' 14 non-insulin-dependent
diabetes mellitus (NIDDM), 15 " 17 and cancer, 18 as
well as with increased all-cause, cardiovascular disease,3"3-8"10-19"21 cancer, 3 and respiratory disease 3 ' 19
mortality. We recently showed that lower levels of both
conditioning leisure time physical activity and maximal
oxygen uptake (V0 2 max) were associated with an
increased risk of acute myocardial infarction (AMI) in
middle-aged men in Eastern Finland.22
From the public health point of view it is more
beneficial if the least active begin to exercise a little
than if the most active do even more. 23 Therefore, it is
of crucial importance to increase leisure time physical
Research Institute of Public Health, University of Kuopio, PO
Box 1627, 70211 Kuopio, Finland and Department of Community
Health and General Practice, University of Kuopio.
86
PHYSICAL ACTIVITY IN SOC1ODEMOGRAPHIC GROUPS
METHODS
Subjects
The Kuopio Ischaemic Heart Disease Risk Factor
Study (KJHD) is a population-based study undertaken
to investigate previously unestablished risk factors for
CHD and extra-coronary atherosclerosis30 among men
in Eastern Finland, a group with one of the highest
recorded risks of CHD.31 The study population is a random sample of men living in the town of Kuopio or
neighbouring rural communities, stratified and balanced according to age, and who were 42, 48, 54, or
60 years old at the baseline examination. The baseline
study was carried out between March 1984 and December 1989. Of 3235 eligible men, 2682 (83%) participated. Complete data on sociodemographic variables
and conditioning leisure time physical activity were
available for 2589 men.
Assessment of Physical Activity
Leisure time physical activity was assessed using a
12-month history, as described in detail previous22.32,33
The 12-month history was modified from the
ly.
Minnesota Leisure Time Physical Activity Questionnaire.34 The checklist included the most common leisure time physical activities of middle-aged Finnish
men, selected on the basis of a previous population
study in Finland.29 For each activity performed, the
subjects were asked to record the frequency (number
of sessions/month), average duration (hours and minutes/session), and intensity (scored as 0 for recreational, 1 for conditioning, 2 for brisk conditioning, and
3 for competitive, strenuous exercise). A trained interviewer collected missing data.
The intensity of physical activity was expressed in
metabolic units (MET or metabolic equivalent of oxygen consumption). The four categories of intensity
of activity (range of possible scores, 0-3) were assigned their own MET values, revised on the basis of a
synthesis of available empiric data. 29 - 3536 The MET
is the ratio of the metabolic rate during exercise to the
metabolic rate at rest. One MET corresponds to an energy
expenditure of approximately 1 kcal/kg x hour and an
oxygen uptake of 3.5 ml/kg x minute. Energy expenditure (in kcal/week) for each activity was calculated by
multiplying the metabolic index of the activity (in
MET x hour/week) by body weight in kilograms.
Physical activity was categorized according to type:
(1) conditioning physical activity—walking (mean
intensity, 4.2 MET), jogging (10.1 MET), skiing (9.6
MET), bicycling (5.8 MET), swimming (5.4 MET),
rowing (5.4 MET), ball games (6.7 MET), and gymnastics, dancing, or weight lifting (5.0 MET); (2) nonconditioning physical activit—crafts, repairs, or
87
building (2.7 MET), yard work, gardening, farming, or
snow shovelling (4.3 MET), hunting, picking berries,
or gathering mushrooms (3.6 MET), fishing (2.4 MET),
and forest activity (7.6 MET); and (3) walking (3.5
MET) and bicycling (5.1 MET) to work. This paper
presents data on only conditioning physical activity, because two other types of leisure time physical activity
were not associated with the risk of AMI.22
Occupational physical activity was assessed using
an interview concerning a typical working day. The
interview was performed for all subjects who had been
working during the last 12 months, whether they were
currently employed or unemployed. The subjects were
asked, with an accuracy of 15 minutes, for how long
they had done the following basic activities: sitting
(given mean intensity, 1.6 MET), standing (2.4 MET),
walking on level ground (3.3 MET), walking on uneven
ground (4.9 MET), climbing stairs (7.3 MET), and other
physical activities (3.9 MET). Occupational energy expenditure was computed by multiplying the metabolic
index of each activity (in MET x hour/day) by body
weight in kilograms and by summing the received
values of energy expenditure.
Data on the reproducibility and validity of the assessments of physical activity have been presented elsewhere.32-33
Assessment of Cardiorespiratory Fitness
Cardiorespiratory fitness was assessed with a maximal
symptom-limited exercise tolerance test on an electrically braked bicycle ergometer for 2280 of all
2589 men. For 616 men examined before June 1986, the
testing protocol comprised a 3-minute warm-up at 50 W
followed by a step-by-step increase in the workload
by 20 W/minute (Tunturi EL 400 bicycle ergometer,
Turku, Finland). The remaining 1664 men were tested
with a linear increase in the workload by 20 W/minute
(Medical Fitness Equipment 400 L bicycle ergometer,
Mearn, the Netherlands).
Respiratory gas exchange was measured in the
616 men by the mixing-chamber method, with use of
a Mijnhardt Oxycon 4 analyser (Mijnhardt, Odijk, the
Netherlands), and in the other 1664 men by the breathby-breath method, with use of a MGC 2001 analyser
(Medical Graphics, St. Paul, Minnesota). The Mijnhardt
Oxycon 4 analyser expressed the V0 2 max as the
average of values recorded over a 30-second period,
whereas the MGC 2001 analyser expressed it as the
average of values recorded over 8 seconds. The
V0 2 max was defined as the highest value for the
plateau in oxygen uptake. The mean V0 2 max was 2.4
1/minute when measured with the Mijnhardt Oxycon 4
analyser and 2.6 1/minute when measured with the
88
INTERNATIONAL JOURNAL OF EPIDEMIOLOGY
MGC 2001 analyser. The intraclass correlation coefficient between simultaneous Mijnhardt Oxycon 4 and
MGC 2001 measurements in 13 men was 0.92, indicating a close correlation.
One cardiologist coded the exercise electrocardiograms (ECG) manually, using the Minnesota code.37
The criteria for evaluating ischaemia on exercise ECG
have been described elsewhere.38
Assessment of Sociodemographics and
Medical History
The place of residence (rural; urban), marital status (married, or engaged; never married, divorced, or widowed),
highest level of education (less than elementary school;
elementary school; junior high school or a part of senior
high school; senior high school or above), longest lifetime occupation (farmers; blue-collar workers; whitecollar workers), and income from the past 12 months
(in quartiles) were recorded with a self-administered
questionnaire, which was checked in an interview. The
subjects were classified as employed if they reported
occupational activity in the occupational physical activity interview. Medical history was assessed as described previously. 38
Statistical Methods
The associations between the duration and mean
intensity of conditioning physical activity and V0 2 max
were estimated with Pearson's correlation coefficients
adjusted for age and examination year. The means of
the physical activity indices and V0 2 max and the statistical significance of their variation over sociodemographic groups were computed with the SPSS-X analysis
of covariance. 39 Three different sets of covariates were
used to analyse the associations of conditioning
physical activity and V0 2 max with the sociodemographic variables: (1) age and examination year;
(2) age, examination year, and medical history
(symptomatic CHD, evidence of ischaemia on exercise
ECG, hypertension, cardiac insufficiency, cardiomyopathy, stroke, claudication, asthma, chronic
bronchitis, cancer, disability due to any chronic
disease); and (3) age, examination year, and occupational energy expenditure. The three sets of covariates
for VO2max were: (1) age and examination year; (2)
age, examination year, and medical history; and (3) age,
examination year, and the duration and mean intensity
of conditioning physical activity. The decrease of
V0 2 max per year of age was estimated and tested for
statistical significance with the SPSS-X least-squares
regression analysis. 39
TABLE 1 Physical activity and maximal oxygen uptake (V02max)
in 2589 middle-aged men in Eastern Finland
Mean
Conditioning physical activity*
Energy expenditure (kcal/week)
988
Duration (hours/week)
2.2
Mean intensity (MET) (n = 2407)
5.8
Occupational physical activity1'
(only employed, n = 1907)
Energy expenditure (kcal/day)
2110
V02max (1/minute) (n = 2280)
2.4
Standard
deviation
Range
1231
2.7
1.8
0-17449
0-26.2
3.0-12.5
903
0.6
0-6099
0 5-5.0
'From the 12-month leisure time physical activity history.
b
From the occupational physical activity interview.
RESULTS
Physical Activity and Maximal Oxygen Uptake
The levels of physical activity and VO2max in the present study population are shown in Table 1. Both the
duration and mean intensity of conditioning physical
activity had an inverse correlation with occupational
energy expenditure (Table 2). The duration and mean
intensity of conditioning physical activity had an inverse correlation with each other. The mean intensity of
conditioning physical activity had a stronger positive
correlation with V0 2 max than the duration of conditioning physical activity. Occupational energy expenditure was not related to V0 2 max.
Sociodemographics and Medical History
The distributions of the sociodemographic variables of
the study population are shown in Table 3. The subjects
ranged in age from 42.0 to 61.3 years (mean 53.0).
Thirty-two out of 1907 subjects who were classified as
employed based on the occupational physical activity
interview reported no income from the past 12 months.
These men had either lost their job or retired but still
had some occupational activity. The subjects who had
any income ranged from 1.500 to 550.000 Finnish marks
(mean 88.421). Of all subjects, 30.1% reported having
hypertension, 27.7% disability due to any chronic disease,
25.2% symptomatic CHD, 7.3% cardiac insufficiency,
7.3% chronic bronchitis, 3.9% claudication, 3.5% asthma,
2.1% cardiomyopathy, 2.0% stroke, and 1.7% cancer.
Evidence of ischaemia on exercise ECG was found in
34.2% of those who underwent the exercise test.
Duration of Conditioning Physical Activity
Men aged either 42, 48, or 54 years had a shorter
duration of physical activity than men aged 60 years
89
PHYSICAL ACTIVITY IN SOCIODEMOGRAPHIC GROUPS
TABLE 2 Age and examination year adjusted intercorrelations between physical activity and maximal oxygen uptake {VO^nax) in 2589
middle-aged men in Eastern Finland
Conditioning physical activity*
Energy expenditure (kcal/week) (1)
Duration (hours/week) (2)
Mean intensity (MET) (3) (n = 2407)
Occupational physical activity'
Energy expenditure (kcal/day) (4)
VOjmax (1/minute) (5) (n = 2280)
(2)
0.90"'
(3)
0.19"*
-0.07*
(4)
-0.13"*
-0.14"*
-0.08"
(5)
0.16""
0.07*
0.32*"
0.03
•P< 0.05, • • P < 0.01, • * • P < 0.001.
•From the 12-month leisure time physical activity history.
b
From the occupational physical activity interview.
(Table 3). Rural men also had a shorter duration of
physical activity than urban men. The duration of physical activity was positively related to income. Furthermore, married or engaged men, employed men, and
fanners had a shorter duration of physical activity than
others. There was no association between the duration
of physical activity and the level of education.
Mean Intensity of Conditioning Physical Activity
There was an inverse and linear association between the
mean intensity of physical activity and age (Table 3).
The mean intensity of physical activity also had positive dose-response relations with the level of education
and income. Additionally, urban, single, and unemployed or retired men, as well as blue-collar workers
had a lower mean intensity of physical activity than
others.
Maximal Oxygen Uptake
There was an inverse and linear association between
V0 2 max and age (Table 3). The V0 2 max decreased by
54 ml/minute per year of age after adjustment for
examination year. The V0 2 max also had positive doseresponse relations with the level of education and income. Furthermore, single men, unemployed or retired
men, blue-collar workers, and farmers had lower
VO2max than others. There was no difference in
V0 2 max between urban and rural men.
The Effect of Adjustments
The association of the duration of conditioning physical activity with age and income disappeared when
occupational energy expenditure was adjusted for. The
durations of conditioning physical activity for men
aged 42, 48, 54, and 60 years were 2.1, 2.3, 2.2, and
2.2 hours/week, respectively, and in the quartiles of
income 2.1, 1.9, 2.0, and 2.2 hours/week, respectively,
after adjustment for work energy expenditure. The difference in the duration of conditioning physical activity
between urban and rural men was weakened, but
remained statistically significant (P < 0.001) when
adjusting for occupational energy expenditure. The duration of conditioning physical activity was 1.6 hours/
week for rural men and 2.3 hours/week for urban
men after this adjustment. Adjustment for occupational
energy expenditure had no effect on the relations of
conditioning physical activity with other sociodemographic factors.
Adjustment for the duration and mean intensity of
conditioning physical activity had no influence on the
associations of V0 2 max with sociodemographic factors. Neither did medical history affect the relations
of conditioning physical activity and VO2max with
sociodemographics.
DISCUSSION
There are no reports of both the duration and intensity
of leisure time physical activity and cardiorespiratory
fitness in different sociodemographic groups of a general population. One reason for this is that truly
quantitative assessments of physical activity and cardiorespiratory fitness have been available in few of the
previous population studies. We assessed physical activity quantitatively by means of a detailed questionnaire, the validity32 and reproducibility33 of which has
been reported elsewhere, and V0 2 max directly, which
is the most accurate and reproducible method for assessing cardiorespiratory fitness.40
Previous studies 424 " 27 have found a shorter duration
of leisure time physical activity in older people. Such
has been the case especially for vigorous exercise.24 One
reason for this is that disability due to chronic diseases decreases the amount of physical activity in older
people. Inconsistently, we observed a shorter duration
of conditioning physical activity in men aged either
42, 48, or 54 years than in men aged 60 years. This suggests that men aged 60 years had no disability that
90
INTCRNATIONAL JOURNAL OF EPIDEMIOLOGY
TABLE 3 The duration and mean intensity of conditioning physical activity" and maximal oxygen uptake in sociodemographic
2589 middle-aged men in Eastern Finland
Maxima] oxygen uptake
Conditioning physical activity'
Duration (hours)
groups of
li/minutej
Mean intensity (MET)
Mean
SD
Mean
SD
Mean
SD
Age
42(12.4%)
48(13.3%)
54 (59.9%)
60 (14.4%)
/"-value
1.9
2.1
2.1
2.6
2.3
2.4
2.7
3.0
6.3
6.0
5.6
5.3
1.7
1.8
1.8
1.5
2.9
2.7
2.3
2.0
0.6
0.6
0.6
0.5
Place of residence
Urban (71.5%)
Rural (28.5%)
P-value
2.5
1.4
Marital status
Married/engaged (86.6%)
Single (13.4%)
P-value
2.1
2.4
Education
Less than elementary (10.0%)
Elementary (47.5%)
Junior high or part of
senior high (35.7%)
Senior high or above (6.8%)
P-value
Employment
Employed (73.7%)
Unemployed/retired (26.3%)
P-value
Occupation
(only employed, n ° 1907)
Blue-collar (39.2%)
White-collar (43.7%)
Farmers (17.1%)
P-value
Income (Finnish marks)
(only employed, n = 1907)
(<58.000)
(58.000-78.000)
(79.000-108.000)
( > 108.000)
P-value
1
b
0.004
< 0.001
< 0.001
2.9
2.0
1.8
1.8
5.7
5.9
2.4
2.4
n.s.
0.05
< 0.001
2.6
3.0
1.8
1.8
5.8
5.4
0.04
0.6
0.6
2.4
2.3
0.6
0.6
< 0.001
< 0.001
2.1
2.1
3.0
2.9
5.6
5.6
1.8
1.7
2.3
2.4
0.6
0.6
22
2.1
2.5
1.9
5.9
6.3
1.8
1.9
2.5
2.6
0.6
0.6
n.s.
1.7
3.3
3.8
2.0
Adjusted for age and examination year.
From the 12-month leisure time physical activity history.
2.5
2.6
2.5
5.7
5.9
6.1
6.3
1.8
1.8
1.8
1.9
< 0.001
0.6
0.6
0.5
< 0.001
< 0.001
2.5
1.9
1.8
1.8
0.6
0.6
< 0.001
1.7
1.8
1.8
5.7
6.2
6.1
< 0.001
0.009
2.4
2.1
< 0.001
2.2
2.0
0.8
1.6
1.6
1.8
2.0
1.5
1.8
5.9
5.1
< 0.001
1.7
2.1
1.1
< 0.001
< 0.001
2.4
2.5
2.6
2.7
0.5
0.6
0.6
0.6
< 0.001
PHYSICAL ACTIVITY IN SOCIODEMOGRAPHIC GROUPS
would have significantly limited their engagement
in physical activity. However, this study in men aged
42-60 years cannot answer the question at what age
a decrease in the amount of exercise begins. Interestingly, the association between the duration of conditioning physical activity and age disappeared when
occupational energy expenditure was adjusted for. This
suggests that men aged 60 years had more time for leisure time physical activity because they were more often
retired than younger men. As in previous studies in
Finnish29 and US men,24 we showed an inverse association between the intensity of physical activity and age.
There are limited data on the association between
leisure time physical activity and the place of residence.
Similarly with the earlier studies in Finnish29 and US
men,24 we found a shorter duration of conditioning physical activity in rural than in urban men. This was partly
due to higher occupational energy expenditure in rural
men, such as fanners and forest workers. Instead,
rural men had a higher intensity of physical activity
than urban men.
Little is known about the association between leisure
time physical activity and marital status.26'27 In the
present study, married or engaged men had a shorter
duration of conditioning physical activity, but a higher
intensity of physical activity and a higher V0 2 max than
single men.
Inconsistently with previous studies,24"26 we did not
find any association between the duration of conditioning physical activity and the level of education.
Instead, there was a positive relation between the duration of conditioning physical activity and income, as
shown earlier.24"26 However, this association disappeared when adjusting for occupational energy expenditure. Few data are available on the associations
between the intensity of physical activity and socioeconomic factors. In our study, the intensity of conditioning physical activity was positively related to
both the level of education and income. Furthermore, blue-collar workers had a lower intensity of
conditioning physical activity than white-collar
workers.
Our data are consistent with those of earlier studies
in which an inverse association has been shown
between leisure time and occupational physical activity.29 Employed men, and especially those who
undertake strenuous work, such as fanners, had a shorter
duration of conditioning physical activity than others.
This suggests that heavy work is an important barrier to
engagement in leisure time physical activity among
middle-aged men. Instead, we found a higher intensity
of physical activity in employed men than in unemployed or retired men.
91
Measuring V0 2 max directly offers the most accurate
and objective method for assessing both physical
activity and cardiorespiratory fitness.40 We observed a
strong inverse association between VO2max and age.
The mean reduction of V0 2 max per year of age was of
the same order as shown earlier.41 Unexpectedly,
neither medical history nor physical activity explained
this relation. This suggests that the decrease of VO2max
with age in men aged 40—60 years is due to ageing
itself, not because of a higher prevalence of chronic
diseases or physical inactivity in older people. The decrease in V0 2 max with age as well as the effect of
chronic diseases is likely to be stronger after the age
of 60 years than in those aged 42-60 years. However,
our study in men aged 42-60 years cannot answer these
questions. There are few previous data on the association of cardiorespiratory fitness with other sociodemographic factors than age. In our study, less educated,
lower income, single and unemployed or retired men, as
well as farmers and blue-collar workers had a lower
V0 2 max than others.
In conclusion, there are large differences in the
levels of conditioning leisure time physical activity
and cardiorespiratory fitness between sociodemographic groups of middle-aged men in Eastern
Finland. On the basis of this study, there is room for
increasing leisure time physical activity and for
improving cardiorespiratory fitness particularly in
those who have a lower socioeconomic position. To
ensure at least a minimum necessary level of physical
activity for health maintenance, health education
programmes should focus especially on these population groups.
ACKNOWLEDGEMENTS
We are indebted to Dr Rainer Rauramaa for the participation of the Kuopio Research Institute of Exercise Medicine in data collection, to Dr Esko Taskinen,
Dr Juha M VanSlainen, Dr Riitta Salonen, Dr Hannu
Litmanen, and Dr Arno Heikeia for their participation
in the supervision of exercise tests, and to Kimmo
Ronkainen for carrying out the data analyses. The
KIHD has been supported by grants from the Finnish
Academy and the Ministry of Education of Finland. Dr
Timo Lakka was supported by grants from the Finnish
Academy, the YrjO Jahnsson Foundation, and Finnish
Medical Foundation.
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