Body Mass Index and Physical Activity in Relation to Mortality Among Adults With Coronary Heart Disease
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CitationAl-Shaar, Laila. 2019. Body Mass Index and Physical Activity in Relation to Mortality Among Adults With Coronary Heart Disease. Doctoral dissertation, Harvard University, Graduate School of Arts & Sciences.
AbstractObesity is a growing epidemic affecting around 40% of the US population and is a major contributor for premature mortality and morbidity. An apparent survival benefit, termed as obesity paradox, has been described among overweight and obese patients with coronary heart disease (CHD), raising doubts about the appropriateness of recommending weight loss as a secondary prevention. Moreover, physical activity (PA) has been associated with lower risk of CHD but evidence for benefits of PA after myocardial infarction (MI) in reducing mortality is limited.
The first paper evaluated the association between BMI and all-cause and CVD mortality among male and female survivors of MI. We found no evidence that excess adiposity was associated with lower mortality. Weight loss from before to after an acute MI without lifestyle improvement was associated with higher mortality.
The second paper evaluated the relationship between PA and mortality among male survivors of MI. Maintaining a high PA or having a long-term increase in PA from before to after MI was associated with lower mortality. Walking for a half hour or more per day after MI was associated with lower mortality independent of walking pace.
Different dietary assessment methods have been used in epidemiologic studies assessing diet-disease relationships. However, these methods are subject to measurement errors thus affecting their ability to measure true intake. The third paper evaluated the performance of a 152-item semiquantitative food frequency questionnaire (SFFQ) as compared to multiple automated self-administered 24-hour dietary recalls (ASA24), two 7-day diet records (7DDR), and several biomarkers in men. The SFFQ performed reasonably well as compared to 7DDR, indicating that the SFFQ has been adequately refined to capture the changes in food supply and eating patterns since its last validation in 1986-1987. The deattenuated correlations of energy-adjusted protein, potassium, sodium, and folate were strongest for the two 7DDRs and similar for the average of four 24-hour recalls, SFFQ’s and one week of 7DDR’s, and lowest for single day of 24-hour recall. Using the method of triads, the estimated correlations of energy-adjusted nutrients assessed by each of the dietary assessment methods and the underlying true intake became stronger.
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