Dairy Consumption and Risk of Stroke in Swedish Women
and Men
Susanna C. Larsson, PhD; Jarmo Virtamo, MD; Alicja Wolk, DMSc
Downloaded from http://stroke.ahajournals.org/ by guest on July 31, 2017
Background and Purpose—Epidemiological studies of the associations of low-fat dairy and specific dairy food
consumption with risk of stroke are sparse. Our aim was to examine the association between consumption of total,
low-fat, full-fat, and specific dairy foods and risk of stroke in a prospective cohort study.
Methods—We followed 74 961 Swedish women and men who were free from cardiovascular disease and cancer and who
completed a 96-item food frequency questionnaire in 1997. Incident cases of stroke were ascertained from the Swedish
Hospital Discharge Registry.
Results—During a mean follow-up of 10.2 years, we ascertained 4089 cases of stroke, including 3159 cerebral infarctions,
583 hemorrhagic strokes, and 347 unspecified strokes. Consumption of low-fat dairy foods was inversely associated
with risk of total stroke (P for trend⫽0.03) and cerebral infarction (P for trend⫽0.03). The multivariable relative risks
for the highest compared with the lowest quintile of low-fat dairy consumption were 0.88 (95% CI, 0.80 – 0.97) for total
stroke and 0.87 (95% CI, 0.78 – 0.98) for cerebral infarction. Consumption of total dairy, full-fat dairy, milk, sour
milk/yogurt, cheese, and cream/crème fraiche was not associated with stroke risk.
Conclusions—These results suggest that low-fat dairy consumption is inversely associated with the risk of stroke. (Stroke.
2012;43:00-00.)
Key Words: dairy 䡲 diet 䡲 epidemiology 䡲 milk 䡲 prospective studies 䡲 stroke
H
igh blood pressure is a major controllable risk factor for
stroke.1 Approximately one third of US adults aged ⱖ18
years has hypertension and only approximately half of all
hypertensives have their blood pressure under control.2 A diet
rich in low-fat dairy foods has been recommended to prevent
and reduce hypertension on the basis of strong evidence.3
Low-fat dairy is 1 of the components of the Dietary Approaches to Stop Hypertension (DASH) diet, which has been
demonstrated to considerably reduce blood pressure.4 Dairy
consumption has also been inversely associated with the
metabolic syndrome in observational studies.5,6
To date, only 1 study has examined the association between
consumption of low-fat dairy foods and risk of stroke and that
study found a nonsignificant inverse association in women.7 In
fact, epidemiological data on total dairy and specific dairy foods
besides milk in relation to stroke risk are very sparse, and
findings are inconsistent.7–9 We therefore examined the association between consumption of total, low-fat, and full-fat dairy foods
as well as specific dairy foods and risk of stroke in a large
population-based prospective study of Swedish women and men.
studies have been described elsewhere.10,11 Briefly, in the Fall of
1997, 39 227 women and 48 850 men who resided in central Sweden
(Uppsala, Västmanland, and Örebro counties) completed a 350-item
questionnaire about diet and other lifestyle factors. For the current
analyses, we excluded participants with an incorrect or a missing
National Registration Number, those with very low or high total
energy intake (ie, 3 SDs from the loge-transformed mean energy
intake; ⬍579 kcal/day and ⬎4664 kcal/day in women and ⬍864
kcal/day and ⬎7277 kcal/day in men), and those with a history of
stroke, coronary heart disease, or cancer at baseline. After exclusions, 74 961 participants (34 670 women and 40 291 men), aged 45
to 83 years, remained for analysis. The study was approved by the
Regional Ethics Committee at the Karolinska Institutet in Stockholm, Sweden.
Baseline Data Collection
The questionnaire included questions about education, weight,
height, smoking, physical activity, aspirin use, history of hypertension and diabetes, family history of myocardial infarction before 60
years, alcohol consumption, and diet. Pack-years of smoking history
were calculated as the number of packs of cigarettes smoked per day
multiplied by the number of years of smoking. Body mass index was
calculated by dividing the weight in kilograms by the square of
height in meters. Participants reported their level of activity at work,
home/housework, walking/bicycling, and exercise in the year before
study enrollment. The questionnaire also included questions on
inactivity (watching TV/reading) and hours per day of sleeping and
sitting/lying down. The time per day reported by the subject to have
engaged in each activity as well as inactivity such as watching TV
Methods
Study Population
The Swedish Mammography Cohort and the Cohort of Swedish Men
provided data for the present analyses. Details about these cohort
Received October 14, 2011; final revision received February 23, 2012; accepted February 24, 2012.
From the Division of Nutritional Epidemiology (S.C.L., A.W.), National Institute of Environmental Medicine, Karolinska Institutet, Stockholm,
Sweden; and the Department of Chronic Disease Prevention (J.V.), National Institute for Health and Welfare, Helsinki, Finland.
Correspondence to Susanna C. Larsson, PhD, Division of Nutritional Epidemiology, Institute of Environmental Medicine, Karolinska Institutet, Box
210, SE-17177 Stockholm, Sweden. E-mail [email protected]
© 2012 American Heart Association, Inc.
Stroke is available at http://stroke.ahajournals.org
DOI: 10.1161/STROKEAHA.111.641944
1
2
Stroke
July 2012
was multiplied by the activity’s typical energy expenditure requirement expressed in metabolic equivalents. The metabolic equivalenthours for all of the individual activities reported by the subject were
then added together to create a metabolic equivalent-hours per day
(24-hour) score.12
Dietary Assessment
Downloaded from http://stroke.ahajournals.org/ by guest on July 31, 2017
Intake of dairy foods was assessed using a self-administered food
frequency questionnaire on which participants reported their average
frequency of consumption of 96 foods and beverages during the past
year. For most food items, 8 categories for frequency of consumption
were provided, ranging from never to ⱖ3 times per day. For some
commonly consumed foods such as milk, sour milk/yogurt, and
cheese, participants could fill in the exact number of servings they
consumed per day or week. Dairy foods included low-fat milk (0.5%
fat), medium-fat milk (1.5% fat), full-fat milk (3% fat), milk in
pancakes, low-fat sour milk/yogurt (0.5% fat), full-fat sour milk/
yogurt (3% fat), cottage cheese (4% fat), low-fat cheese (10%–17%
fat), full-fat cheese (approximately 28% fat), ice cream, cream, and
crème fraiche. Depending on age and sex, portion sizes for different
dairy foods were: milk, 87 to 149 g for women and 153 to 261 g for
men; sour milk/yogurt, 184 to 218 g for women and 185 to 343 g for
men; cheese (excluding cottage cheese), 17 to 24 g for women and
18 to 28 g for men; and cream and cream fraiche, 19 to 23 g for
women and 29 to 43 g for men. In a validation study of a previous
food frequency questionnaire, the Pearson correlation coefficients
for dairy foods between the food frequency questionnaire and 4
1-week diet records (completed 3– 4 months apart) ranged from 0.4
for cheese to 0.7 for sour milk/yogurt (A. Wolk, unpublished data).
Ascertainment of Stroke Cases
Incident cases of first stroke were ascertained by linkage of the study
population with the Swedish Hospital Discharge Registry, which
provides nearly complete coverage of the discharges. The strokes
were classified as cerebral infarction (International Classification of
Diseases 10th Revision code I63), intracerebral hemorrhage (I61),
subarachnoid hemorrhage (I60), and unspecified stroke (I64). Information on dates of death for participants who died was obtained from
the Swedish Death Register.
Statistical Analysis
Person-time of follow-up for each participant was computed from
January 1, 1998, until the date of the first stroke event, death, or end
of follow-up (December 31, 2008), whichever came first. Participants were grouped into quintiles of dairy food consumption based
on the distribution in the cohort. We used Cox proportional hazards
regression models to estimate relative risks (RRs) with 95% CIs of
total stroke, cerebral infarction, and hemorrhagic stroke. Because
separate analyses for women and men showed similar patterns of
association (P for interaction by sex ⬎0.16 for total dairy, low-fat
and full-fat dairy, and each dairy food), we present results for women
and men combined with adjustment for sex as a stratum variable in
the Cox model to allow for different baseline hazard rates. All
analyses were also controlled for age (in months) as a stratum
variable. In multivariable models, we further adjusted for smoking
status and pack-years of smoking (never; past ⬍20, 20 –39, or ⱖ40
pack-years; or current ⬍20, 20 –39, or ⱖ40 pack-years), education
(less than high school, high school, or university), body mass index
(⬍20, 20 –24.9, 25–29.9, or ⱖ30 kg/m2), total physical activity
(metabolic equivalent-hours/day, quintiles), aspirin use (never, 1– 6
tablets/week, ⱖ7 tablets/week), history of hypertension (yes or no),
history of diabetes (yes or nor), family history of myocardial
infarction before 60 years of age (yes or no), intakes of total energy
(kcal/day, continuous variable), and quintiles of alcohol, coffee,
fresh red meat, processed meat, fish, fruits, and vegetables. We
tested the proportional hazard assumption and found no departure
from this assumption for the exposures.
Tests for trends were performed by assigning the median value for
each quintile and modeling this variable as a continuous variable. We
conducted analyses stratified by history of hypertension, obesity, and
diabetes. Test for interaction was conducted by using the likelihood
ratio test. In a sensitivity analysis, we removed history of hypertension from the multivariable model because hypertension is a potential intermediate of the association between dairy consumption and
stroke risk. We also repeated the analyses after excluding the first 2
years of follow-up. The analyses were conducted with SAS Version
9.2 (SAS Institute, Cary, NC). All statistical tests were 2-sided.
Probability values ⬍0.05 were considered statistically significant.
Results
During a mean follow-up of 10.2 years, we ascertained 4089
stroke cases (1680 in women and 2409 in men), including
3159 cerebral infarctions, 583 hemorrhagic strokes, and 347
unspecified strokes. Baseline characteristics of the study
population by total dairy food consumption are presented in
Table 1. Compared with women and men with low dairy food
consumption, those with high consumption were slightly less
likely to have a history of hypertension and had, on average,
a higher total energy intake and consumed more coffee and
red meat. Other characteristics did not vary appreciably
across categories of dairy food consumption.
The association between dairy foods and risk of total stroke
and stroke subtypes are shown in Table 2. Low-fat dairy food
consumption was statistically significantly inversely associated with risk of total stroke and cerebral infarction. Compared with women and men in the lowest quintile of low-fat
dairy food consumption, those in the highest quintile had a
12% (95% CI, 3%–20%) lower risk of total stroke, and a 13%
(95% CI, 2%–22%) lower risk of cerebral infarction. The
results persisted when we excluded the first 2 years of
follow-up (total stroke: RR, 0.89; 95% CI, 0.80 – 0.99, for
highest versus lowest quintile) and did not change when we
removed history of hypertension (a potential intermediate)
from the model. In multivariable model, no statistically
significant inverse association was observed between total
dairy, full-fat dairy, total milk, sour milk/yogurt, cheese, or
cream/crème fraiche and risk of total stroke, cerebral infarction, or hemorrhagic stroke. None of the low-fat dairy items
were statistically significantly associated with risk of stroke.
Low-fat dairy food consumption was positively correlated
with minerals and vitamins found in dairy foods such as
calcium (Spearman r⫽0.48), potassium (r⫽0.36), magnesium (r⫽0.32), and vitamin D (r⫽0.40). After adding calcium intake to the multivariable model, the RR of total stroke
for the highest versus the lowest quintile of low-fat dairy food
consumption was 0.81 (95% CI, 0.71– 0.92). Further adjustment for dietary potassium, magnesium, and vitamin D did
not change the results materially (corresponding RR, 0.80;
95% CI, 0.70 – 0.92). The relation between low-fat dairy food
consumption and total stroke was not modified by history of
hypertension (P for interaction⫽0.52), obesity (P for interaction⫽0.37), or diabetes (P for interaction⫽0.50).
Discussion
In this large prospective cohort study, low-fat dairy consumption was inversely associated with risk of total stroke and
cerebral infarction. Low-fat dairy food consumption showed
a dose–response relation with the risk of cerebral infarction,
whereas it seemed to be a threshold effect for total stroke. We
observed no association between consumption of total dairy,
Larsson et al
Table 1.
Dairy Foods and Stroke
3
Baseline Characteristics According to Total Dairy Food Consumption*
Total Dairy, Servings/D
Characteristic
⬍3.1
(n⫽15 090)
3.1– 4.2
(n⫽15 029)
4.3–5.5
(n⫽15 246)
5.6 –7.4
(n⫽15 107)
ⱖ7.5
(n⫽14 489)
Age, y
59.6
60.3
60.8
60.9
59.9
Sex, % men
51.8
48.5
51.4
56.0
61.5
Postsecondary education, %
16.9
18.6
19.2
19.0
17.9
Current smoker, %
27.7
23.4
22.6
23.3
25.2
Body mass index, kg/m2
25.5
25.3
25.3
25.3
25.5
Total physical activity, MET-h/d†
41.7
41.8
42.0
42.3
42.7
History of hypertension, %
19.9
22.3
21.1
20.6
20.2
History of diabetes, %
6.7
5.7
5.6
5.5
6.5
Family history of MI, %
16.1
15.9
14.9
15.0
15.1
6.7
6.7
6.8
6.7
6.7
Aspirin use, ⱖ7 tablets/wk, %
Dietary variables
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Total energy, kcal/d
1709
1945
2173
2451
3013
Alcohol, g/d
7.8
7.5
7.6
7.6
7.5
Coffee, cups/d
2.8
3.0
3.1
3.3
3.6
Fresh red meat, g/d
48.8
48.5
50.2
52.3
54.8
Processed meat, g/d
32.4
33.9
35.4
36.7
38.2
Fish, servings/d
0.3
0.3
0.3
0.3
0.3
Fruits, servings/d
1.6
1.7
1.8
1.8
1.8
Vegetables, servings/d
2.6
2.7
2.8
2.8
2.8
MET indicates metabolic equivalent; MI, myocardial infarction.
*All values (except age) were standardized to the age distribution of the study population in 1997. Total dairy included low-fat milk,
medium-fat milk, full-fat milk, milk in pancakes, low-fat sour milk/yogurt, full-fat sour milk/yogurt, low-fat cheese, full-fat cheese,
cottage cheese, ice cream, cream, and crème fraiche.
†Total activity (MET-h/d) includes activity at work, home/housework, walking/bicycling, and exercise as well as take into account
inactivity (watching TV/reading), and hours per d of sleeping and sitting/lying down.
full-fat dairy, sour milk/yogurt, cheese, or cream/crème
fraiche and stroke risk.
The observed reduction in risk of stroke associated with
high consumption of low-fat dairy foods may be mediated
through a reduction in blood pressure. Studies in humans and
hypertensive rats show that intake of fermented milk or milk
protein-derived peptides can have significant hypotensive
effects.13 A randomized double-blind crossover trial among
352 adults with prehypertension or Stage 1 hypertension
showed that compared with carbohydrate controls, milk
protein supplementation was associated with a statistically
significant 2.3 mm Hg (⫺3.7 to ⫺1.0 mm Hg; P⫽0.0007) net
change in systolic blood pressure.14 Results from another
randomized trial among 70 white subjects showed that daily
consumption of 2 capsules containing isoleucine–proline–
proline-rich milk protein hydrolysates (7.5 mg isoleucine–
proline–proline per capsule) lowered systolic blood pressure
by 3.8 mm Hg (P⫽0.008) and diastolic blood pressure by
2.3 mm Hg (P⫽0.007) compared with placebo (containing
cellulose) in subjects with Stage 1 hypertension.15 A metaanalysis of 5 cohort studies involving nearly 45 000 participants and 11 500 cases with elevated blood pressure showed
a statistically significant 13% lower risk of elevated blood
pressure associated with high consumption of dairy foods
(RR, 0.87; 95% CI, 0.81– 0.94).16 Separation of high- and
low-fat dairy foods indicated an inverse association with
low-fat dairy foods only (RR, 0.84; 95% CI, 0.74 – 0.95).16
That finding is consistent with results from our study showing
an inverse association between consumption of low-fat dairy
but not full-fat dairy and stroke risk.
Low-fat dairy foods are fortified with vitamin D in Sweden. We have observed that consumption of low-fat dairy
foods is an important predictor of serum concentrations of
25-hydroxyvitamin D during winter among women in the
Swedish Mammography Cohort.17 Results from a meta-analysis indicated that blood 25-hydroxyvitamin D concentration
is inversely associated with hypertension,18 which is a strong
risk factor for stroke. Hence, it is possible that vitamin D in
low-fat dairy, at least in part, may explain the observed
inverse association between low-fat dairy and risk of stroke in
the present study.
Full-fat dairy foods may counteract a potential beneficial
effect of dairy consumption on stroke by increasing total and
low-density lipoprotein cholesterol concentrations. In fact,
findings from randomized control trials of parallel or crossover design indicated that replacement of saturated fat derived from full-fat dairy foods with low-fat dairy lowers
low-density lipoprotein/high-density lipoprotein cholesterol
and total/high-density lipoprotein cholesterol ratios.19 It has
been suggested that a very low intake of saturated fat
increases the risk of intraparenchymal hemorrhage.20 Full-fat
dairy is a source of both saturated fat and thus may be
4
Stroke
Table 2.
July 2012
Relative Risks of Stroke by Quintiles of Dairy Food Consumption in 74 961 Swedish Women and Men, 1998 –2008
Total Stroke
Cerebral Infarction
Hemorrhagic Stroke
Servings/D
(Median)
No. of
Cases
Person-Y
RR
(95% CI)*
RR
(95% CI)†
No. of
Cases
RR
(95% CI)†
No. of
Cases
RR
(95% CI)†
Q1
2.3
822
153 907
1.00
1.00
620
1.00
122
1.00
Q2
3.7
757
154 422
0.85 (0.77–0.93)
0.88 (0.79–0.97)
589
0.90 (0.80–1.01)
94
0.74 (0.56–0.98)
Q3
5.0
877
156 066
0.92 (0.83–1.01)
0.96 (0.86–1.06)
692
1.01 (0.90–1.14)
117
0.86 (0.65–1.12)
Q4
6.4
858
154 056
0.89 (0.81–0.98)
0.93 (0.84–1.04)
684
0.98 (0.87–1.11)
114
0.84 (0.63–1.12)
Q5
9.3
775
148 201
0.89 (0.80–0.98)
0.91 (0.80–1.03)
574
0.91 (0.79–1.05)
136
1.03 (0.75–1.42)
0.12
0.41
Dairy by Quintile
Total dairy
P for trend
0.48
0.45
Low-fat dairy‡
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Q1
0
1179
181 226
1.00
1.00
908
1.00
167
1.00
Q2
0.4
511
122 527
0.90 (0.81–1.00)
0.91 (0.82–1.02)
403
0.94 (0.83–1.06)
73
0.87 (0.65–1.16)
Q3
1.0
815
165 681
0.90 (0.83–0.99)
0.92 (0.84–1.02)
625
0.92 (0.82–1.02)
114
0.91 (0.71–1.17)
Q4
2.0
768
141 220
0.92 (0.84–1.00)
0.91 (0.82–1.00)
595
0.90 (0.81–1.00)
110
0.97 (0.75–1.24)
Q5
4.0
816
155 999
0.91 (0.83–0.99)
0.88 (0.80–0.97)
628
0.87 (0.78–0.98)
119
0.96 (0.74–1.25)
0.14
0.03
P for trend
0.03
0.93
Full-fat dairy§
Q1
0.8
783
157 329
1.00
1.00
600
1.00
111
1.00
Q2
2.2
805
155 120
0.94 (0.85–1.04)
0.98 (0.88–1.08)
616
0.98 (0.87–1.11)
114
0.96 (0.73–1.26)
Q3
3.2
831
152 692
0.92 (0.83–1.02)
0.97 (0.87–1.07)
649
1.00 (0.88–1.12)
112
0.90 (0.68–1.19)
Q4
4.5
872
153 069
0.94 (0.85–1.04)
0.97 (0.87–1.08)
691
1.04 (0.92–1.17)
112
0.81 (0.61–1.09)
Q5
7.0
798
148 443
0.92 (0.83–1.01)
0.94 (0.83–1.07)
603
0.97 (0.84–1.12)
134
0.99 (0.72–1.37)
0.15
0.46
P for trend
0.91
0.90
Milk㛳
Q1
0.1
879
149 437
1.00
1.00
674
1.00
132
1.00
Q2
0.3
768
148 072
0.93 (0.85–1.03)
0.94 (0.85–1.04)
598
0.95 (0.85–1.06)
105
0.89 (0.69–1.16)
Q3
1.1
619
137 812
0.86 (0.78–0.96)
0.89 (0.80–0.99)
471
0.88 (0.77–0.99)
82
0.80 (0.60–1.07)
Q4
1.9
903
168 980
0.94 (0.85–1.03)
0.95 (0.86–1.04)
700
0.94 (0.84–1.06)
125
0.94 (0.73–1.22)
Q5
3.1
920
162 351
0.92 (0.84–1.01)
0.90 (0.82–1.00)
716
0.90 (0.80–1.00)
139
0.99 (0.76–1.27)
0.27
0.12
234 685
1.00
1.00
1064
1.00
209
1.00
0.77 (0.56–1.07)
P for trend
0.13
0.76
Sour milk and yogurt
Q1
0
1395
Q2
0.3
346
82 339
0.90 (0.80–1.02)
0.95 (0.84–1.07)
272
0.98 (0.86–1.13)
46
Q3
0.6
632
124 429
0.98 (0.89–1.08)
1.05 (0.95–1.16)
476
1.04 (0.93–1.17)
96
1.02 (0.79–1.32)
Q4
1.0
929
176 608
0.92 (0.84–1.00)
1.02 (0.93–1.11)
731
1.05 (0.95–1.16)
113
0.82 (0.64–1.04)
Q5
2.0
787
148 592
0.90 (0.83–0.98)
0.98 (0.90–1.08)
616
1.02 (0.92–1.14)
119
0.92 (0.72–1.17)
0.03
0.99
P for trend
0.54
0.48
Cheese¶
Q1
0.4
706
127 058
1.00
1.00
527
1.00
109
1.00
Q2
1.1
594
114 757
0.89 (0.80–1.00)
0.94 (0.84–1.05)
461
0.99 (0.87–1.12)
82
0.82 (0.61–1.09)
Q3
2.0
1158
208 090
0.87 (0.79–0.96)
0.93 (0.85–1.03)
921
1.00 (0.90–1.12)
136
0.71 (0.54–0.92)
Q4
3.0
491
83 432
0.87 (0.77–0.97)
0.95 (0.84–1.07)
382
1.00 (0.87–1.14)
67
0.84 (0.61–1.15)
Q5
5.0
1140
233 315
0.86 (0.78–0.94)
0.91 (0.81–1.01)
868
0.95 (0.84–1.08)
189
0.87 (0.66–1.14)
0.02
0.11
P for trend
0.34
0.90
(Continued)
Larsson et al
Table 2.
Dairy Foods and Stroke
5
Continued
Total Stroke
Dairy by Quintile
Servings/D
(Median)
Cerebral Infarction
Hemorrhagic Stroke
No. of
Cases
Person-Y
RR
(95% CI)*
RR
(95% CI)†
No. of
Cases
RR
(95% CI)†
No. of
Cases
RR
(95% CI)†
Cream and crème fraiche
Q1
0
985
129 575
1.00
1.00
766
1.00
128
1.00
Q2
0.07
928
163 057
0.92 (0.84–1.01)
0.96 (0.87–1.06)
713
0.95 (0.85–1.06)
142
1.01 (0.79–1.30)
Q3
0.13
723
180 259
0.84 (0.76–0.93)
0.94 (0.84–1.04)
541
0.91 (0.81–1.03)
102
0.83 (0.62–1.10)
Q4
0.28
871
184 813
0.83 (0.75–0.91)
0.92 (0.83–1.01)
678
0.93 (0.83–1.04)
127
0.90 (0.69–1.17)
Q5
0.50
582
108 948
0.90 (0.81–1.00)
1.00 (0.89–1.12)
461
1.05 (0.92–1.19)
84
0.93 (0.69–1.25)
0.02
0.89
P for trend
0.39
0.53
Downloaded from http://stroke.ahajournals.org/ by guest on July 31, 2017
RR indicates relative risk; Q, quintile.
*Adjusted for age and sex.
†Adjusted for age, sex, smoking status, and pack-y of smoking, education, body mass index, total physical activity, aspirin use, history of hypertension, diabetes,
family history of myocardial infarction, and intakes of total energy, alcohol, coffee, fresh red meat, processed meat, fish, fruits, and vegetables. Low-fat dairy and
full-fat dairy were mutually adjusted by including both variables in the same multivariable model. Similarly, the individual dairy foods, including milk, sour milk/yogurt,
cheese, and cream/crème fraiche, were mutually adjusted. Total dairy is not adjusted for individual dairy foods.
‡Low-fat milk, medium-fat milk, low-fat sour milk or yogurt, cottage cheese, and low-fat cheese.
§Full-fat milk, full-fat sour milk or yogurt, full-fat cheese, ice cream, cream, and crème fraiche.
㛳Low-fat milk, medium-fat milk, full-fat milk, and milk in pancakes.
¶Low-fat cheese and full-fat cheese.
associated with intraparenchymal hemorrhage. We observed
no association between full-fat dairy food consumption and
risk of total hemorrhagic stroke or intraparenchymal hemorrhage (data not shown) in the present study.
Only 1 study has to our knowledge examined the association between low-fat dairy and risk of stroke. In that Dutch
cohort study with 10 years of follow-up and 520 and 322
deaths of stroke in men and women, respectively, consumption of low-fat dairy foods was nonsignificantly inversely
associated with stroke mortality in women (per 100-g/day
increase: RR, 0.94; 95% CI, 0.88 –1.01) but not in men (RR,
1.01; 95% CI, 0.95–1.08).7 Total and low-fat dairy consumption was slightly lower in the Dutch cohort7 than in the
current study, and dairy was analyzed in grams per day.
Previous studies of total dairy and/or specific dairy foods
in relation to stroke incidence or mortality have yielded
inconsistent results. Total dairy food consumption was inversely associated with risk of stroke in a Japanese cohort21
but not in a cohort of Finnish men9 or in Dutch men and
women.7 With regard to milk, a recent meta-analysis found
no significant association between total milk consumption
and stroke risk (RR, 0.87; 95% CI, 0.72–1.07, per 200-mL/
day increase).22 Among 3 studies that assessed cheese consumption in relation to stroke risk, a statistically significant
inverse association was observed in 1 study8 but not in the 2
other studies.7,9 The reason for the inconsistent results is
unclear but may be related to the small number of stroke cases
in some previous studies,7,23–25 leading to unstable risk
estimates. Furthermore, differences in the amount and type of
dairy food consumed in different populations may in part
account for the inconsistent findings.
Populations in the northern parts of Europe and North
America have traditionally consumed much more dairy foods
than other populations. Sweden is among the top 5 countries
in the world with the highest per-capita consumption of dairy
foods. Particularly cheese and sour milk/yogurt consumption
is high in the Swedish population.26 In Sweden, dairy foods
are consumed as a side dish. Cheese is usually consumed
sliced on sandwiches and sour milk is often consumed with
cereals.
Our study has several strengths, including its populationbased and prospective design, the large sample size (largest
study to date on dairy foods and stroke), the detailed data on
diet, and the completeness of case ascertainment through
linkage to Swedish registries. The prospective design eliminates recall bias and the virtually complete follow-up minimized the likelihood that our findings have been affected by
bias due to differential follow-up. A limitation is that only
baseline data were used and participants may have changed
dairy food consumption during follow-up leading to attenuated risk estimates. Although we controlled for the most
important known risk factors for stroke, we cannot exclude
the possibility that the observed inverse association between
low-fat dairy foods and stroke is due to unknown confounders
or residual confounding. The similar results in age- and
sex-adjusted and in multivariable models argue against residual confounding.
In summary, findings from this large study suggest that
low-fat dairy food consumption is inversely associated with
risk of stroke. Further large prospective studies of low-fat
dairy foods in relation to stroke are needed to establish a
potential association.
Sources of Funding
This study was supported by a research grant from the Swedish
Council for Working Life and Social Research (FAS), the Swedish
Research Council, and by a Research Fellow grant from Karolinska
Institutet (to Dr Larsson). The funders had no role in the design and
conduct of the study; collection, management, analysis, and interpretation of the data; or preparation, review, or approval of the
article.
Disclosures
None.
6
Stroke
July 2012
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Dairy Consumption and Risk of Stroke in Swedish Women and Men
Susanna C. Larsson, Jarmo Virtamo and Alicja Wolk
Stroke. published online April 19, 2012;
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