Muscle strength and body size and later cerebrovascular and coronary heart disease.

OBJECTIVE

To investigate the associations between muscle strength, relative weight, and stature in young adulthood with later coronary heart disease (CHD) and stroke incidence.

DESIGN

Cohort study.

SETTING

Baseline data were drawn from the Swedish Military Service Conscription Register from the records of 1969 to 1994.

PARTICIPANTS

At baseline, male Swedish citizens born between 1951 and 1976 (median age, 18.2 y) attended a mandatory conscription examination from which the only grounds for exemption were a severe handicap or a chronic disease. Full data sets with blood pressure in the acceptable range [diastolic (DBP), 40-100 mm Hg and systolic (SBP), 100-180 mm Hg] were available for 1 145 467 men (99%).

ASSESSMENT OF RISK FACTORS

The conscription examination included measurements of elbow flexion, hand grip, and knee extension strength; DBP and SBP, and height and weight for calculation of body mass index (BMI). Data on education and socioeconomic status were derived from censuses conducted every decade.

MAIN OUTCOME MEASURES

The main outcome measures were fatal and nonfatal CHD events and hemorrhagic and ischemic strokes in relation to strength, BMI, and height. Follow-up data were collected from 1969 to 2006 from the Swedish Cause of Death Register, Swedish Hospital Discharge Register, and Statistics Sweden's Emigration Register. Follow-up time was counted from conscription examination to death or hospitalization (median follow-up time, 24.4 y). Standardized hazard ratios (HR) were calculated for a 1-SD increase in the exposure variables.

MAIN RESULTS

During the follow-up period 12 323 CHD and 8865 stroke cases occurred. After adjustment for other risk factors, strength indicators were inversely associated with CHD and all strokes (HR for CHD: elbow flexion strength, 0.95; 95% confidence interval [CI], 0.93-0.97; grip strength, 0.89; 95% CI, 0.88-0.91; knee extension strength, 0.92; 95% CI, 0.90-0.94; and HR for stroke: elbow flexion strength, 0.96; 95% CI, 0.94-0.99; grip strength, 0.95; 95% CI, 0.93-0.97; knee extension strength, 0.93; 95% CI, 0.90-0.95). Greater grip strength predicted a lower risk of intracerebral infarction (HR, 0.91; 95% CI, 0.88-0.95) and greater knee extension strength predicted a lower risk of intracerebral and subarachnoid hemorrhagic stroke (HR, 0.88; 95% CI, 0.82-0.93 and HR, 0.92, 95% CI, 0.86-0.99, respectively). Risk of CHD and intracerebral infarction increased progressively with increasing BMI, whereas both very low BMI and overweight were associated with intracerebral and subarachnoid hemorrhagic stroke. Tallness was positively associated with lower rates of CHD and stroke.

CONCLUSIONS

Muscle strength was inversely associated with risk of fatal and nonfatal coronary heart disease and stroke, independently of associations of BMI and stature with mortality and morbidity, during 24 years of follow-up of men on Swedish conscription rolls.