Older Americans are the most rapidly growing age group, and also the least physically active. Physical activity (PA) has been shown to reduce the risk of CVD events, functional disability, cognitive decline, and all-cause mortality. PA guideline and most epidemiologic studies have focused on 'moderate-to-vigorous physical activity', but there is emerging evidence that an overall sedentary lifestyle may be adversely associated with cardiovascular health regardless of PA levels. Current research on the impact of PA on health outcomes in older adults is limited in 4 major ways: 1) inaccurate measurement methodology; 2) lack of data on health effects of sedentary behavior, independent of PA; 3) missing detailed assessment of PA 'dose-response' relations; 4) scant data on how PA mitigates target organ damage that is a frequent precursor of overt CVD.
The specific aims of this application are as follows:
Aim 1. To characterize the distributions of intensity and patterns of both PA and sedentary behavior, measured objectively with an omni-directional accelerometer over a 5-7 day period, in 3000 older white and non-white participants in the community-based Framingham Heart Study (mean age 75 years); and to relate these measures to CVD risk factors.
Aim 2. To relate objectively measured sedentary behavior and intensity/patterns of PA to measures of cardiac structure and function (assessed by echocardiography), large artery stiffness (via applanation tonometry), brain structure (via MRI) and cognitive function, and renal function (24-hour albumin excretion and estimated glomerular filtration rate). We will relate total PA and sedentary behavior to these measures of target organ damage.
Aim 3. To relate intensity and patterns of objectively measured PA and sedentary behavior to incident CVD events (coronary heart disease, stroke, and heart failure), dementia and all-cause mortality prospectively. Our application to analyze extant accelerometry data in a previously enrolled large aging multiethnic community-based cohort under continuous longitudinal surveillance will bridge a fundamental and critical gap in our current knowledge regarding the health benefits of PA (intensity and patterns) and the relationship of a sedentary lifestyle with health outcomes in older people. We will elucidate the impact of PA on target organ damage, and establish a scientific resource that will contribute to the evidence base for future public health recommendations and clinical guidelines for PA in older adults.
We propose to analyze extant physical activity data collected using an accelerometer in approximately 3000 Framingham Heart Study participants and look at how physical activity and sedentary behavior affect risk factors for heart disease, and occurrence of heart attacks and strokes. Our study would help older Americans and their doctors decide how often, how long, and how intensely to exercise for better health outcomes.
