The Joint Effects of Physical Activity and Body Mass Index on Coronary Heart Dis

July 20, 2008

The Joint Effects of Physical Activity and Body Mass Index on Coronary

Heart Disease Risk in Women

Amy R. Weinstein, MD, MPH; D. Sesso, ScD, MPH; I-Min Lee, MBBS,

ScD; M. Rexrode, MD, MPH; R. Cook, ScD; JoAnn E. Manson,

MD, DrPH; E. Buring, ScD; J. Gaziano, MD, MPH

Arch Intern Med. 2008;168(8):884-890.

ABSTRACT

Background Physical activity and body mass index (calculated as

weight in kilograms divided by height in meters squared) independently

alter the risk of coronary heart disease (CHD); however, their

combined effect on CHD is not established. Our objective was to study

the combined association of physical activity and body mass index on CHD.

Methods Prospective cohort study of 38 987 women free of

cardiovascular disease, cancer, and diabetes at baseline in the

Women's Health Study, with 10.9 mean years of follow-up. Weight,

height, and recreational activities were reported on entry. Body mass

index was categorized as normal weight (<25), overweight (25 to <30),

and obese ( & #8805;30). Active was defined as 1000 kilocalories or more

expended on recreational activities weekly. Six joint body

weight–physical activity categories were defined. The main outcome

measure was the occurrence of incident CHD during follow-up, defined

as a cardiovascular event including nonfatal myocardial infarction,

coronary artery bypass graft, percutaneous transluminal coronary

angioplasty, or CHD death.

Results A total of 948 cases of incident CHD occurred during

follow-up. Higher body mass index and physical inactivity were

individual predictors of CHD. In joint analyses, compared with active

normal-weight individuals, the multivariate-adjusted hazard ratios

(95% confidence intervals) were 1.54 (1.14-2.08) for

overweight-active; 1.87 (1.29-2.71) for obese-active; 1.08 (0.84-1.39)

for normal weight–inactive; 1.88 (1.46-2.42) for overweight-inactive;

and 2.53 (1.94-3.30) for obese-inactive. Increasing levels of walking

also resulted in significant reductions in CHD risk for overweight and

obese individuals.

Conclusions The risk of CHD associated with elevated body mass index

is considerably reduced by increased physical activity levels.

However, the risk is not completely eliminated, reinforcing the

importance of being lean and physically active.

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