Physical activity, visceral adipose tissue, and cardiovascular disease in older adults: associations and effects

BACKGROUND: Cardiovascular disease (CVD) poses a substantial public health burden and is the leading cause of mortality in older adults. With the population aging rapidly, interventions aimed at improving modifiable risk factors for CVD, such as physical inactivity and visceral obesity, could play an important role in reducing its burden, provided they are proven effective. PURPOSE AND AIMS: The overall purpose of this thesis was to create a deeper understanding of the links between physical activity, visceral adipose tissue (VAT), and CVD in older adults, by studying it from both an observational and an interventional perspective. The specific aims were to investigate the associations of objectively measured physical activity and VAT with the risk of CVD and all-cause mortality, to investigate the effect of structured physical activity (exercise) on VAT, and to review the effects of exercise on CVD and all-cause mortality based on evidence from randomized controlled trials (RCTs). METHODS: This thesis comprised two prospective cohort studies, one RCT, and one narrative review of evidence from RCTs. The cohort studies included about 3,300 men and women aged 70 years with baseline data on physical activity and VAT mass, as obtained using accelerometry and dual-energy X-ray absorptiometry, respectively. Cases of stroke, myocardial infarction, and all-cause mortality during follow-up were collected from Swedish nationwide registers. The RCT included 77 men and women aged 70 years with visceral obesity who were randomly allocated to either 10 weeks of supervised vigorous-intensity exercise or to no exercise, with VAT mass measured before and after the intervention. In the review, evidence from published RCTs and meta-analyses of RCTs reporting on the effects of exercise on CVD (N=19,162) and all-cause mortality (N=37,443) in general older adults and in individuals with chronic conditions (such as obesity, type 2 diabetes, and preexisting CVD) were reviewed. MAIN FINDINGS: In the cohort studies, greater amounts of physical activity of any intensity, but especially that of moderate to vigorous intensity, were associated with lower risk of stroke, myocardial infarction, and all-cause mortality. Conversely, greater VAT mass was associated with higher risk of stroke or myocardial infarction. In the RCT, short-term vigorous-intensity exercise seemed to decrease VAT mass slightly, but the effect was not statistically significant. Finally, the review showed that there