Study Of Physical Activities In The Blsa

Aging

Investigators

Linked publications & trials

Abstract

Over the past year, we have reported the relationship between physical activity and cardiovascular fitness as estimated by VO2max. Based on currently accepted estimates of oxygen utilization for specific physical activities, the time Baltimore Longitudinal Study of Aging subjects spent doing 100 activities was converted to METS*minutes. METS is a standard way to express oxygen utilization that adjusts for body size. The 100 activities were then divided into three categories: low level activity (<4 METS), moderate level activity (4-6 METS), and high level activity (>6 METS). Cardiovascular fitness was significantly correlated with high level activity (r=.32), moderate level activity (r=.15), body size (BMI) (r=-.32), and age (r=-.58). In multivariate analysis with these variables, physical activity independently explained 1.6% of the variance in VO2max while sharing about 10% of the variance with age and BMI. Using the regression models, we estimate that for an average individual to increase their VO2max 10% requires 35-40 minutes a day of high level activity and 150 minutes a day of moderate level activity. These calculations support the general concept of the recent Surgeon General recommendations for daily physical activity. We examined the impact of national recommendations on leisure time physical activities (LTPA) in healthy men (n=1359) from 1958 to 1998 and in healthy women (n=840) from 1978 to 1998, who were participants of the Baltimore Longitudinal Study of Aging (BLSA). The prevalence of a sedentary lifestyle in each decade was assessed based on compliance with widely publicized recommendations for participation in physical activity. High intensity LTPA, defined as activities >6 METS, showed an increase in median daily values from the 1960s to the 1990s for men with most of the change between the 1960s and 1970s, but did not change between the 1970s and the 1990s in women. Moderate intensity LTPA, defined as 4-5.9 METS, did not change significantly over these periods in either sex. Adjustment for age, education and race did not affect these findings. The percentage of sedentary men, defined as those performing < 40 MET-minutes/day of high intensity LTPA, declined across the four decades whereas for women it did not change significantly. For those over 60 years old, time trends in high intensity LTPA resembled those for the entire sample with a significant increase in men but not in women. Thus, in healthy subjects across a broad age range, national recommendations appear to have made modest progress in decreasing the proportion of sedentary BLSA men whereas women have not changed. We have examined whether the level of cardiovascular fitness or physical activity are independent risk factors for mortality in men. Cardiovascular fitness, as assesse by VO2max, is a strong independent contributor to both all cause and cardiac mortality. Physical activity is important, not to the same degree as fitness. Of interest, high intensity physical activity was an independent risk factor in older men (>60 years) but not younger men, while cardiovascular fitness was important at all ages. If physical activity is important for survival and fitness, should we judge the levels of activity based on an absolute scale, or on an age-adjusted scale. We have explored this question in the BLSA, and found that by using an absolute scale, there is an age-associated decrement in the levels of physical activity. Using an age-adjusted scale, the level of physical activity increases with increasing age. While relative scales may be of value in examining the relationships between activity and well being, they lead to the wrong conclusions regarding the physical capacity of the elderly. We have completed an intervention in patients with osteoarthritis of the knee to motivate increased activity. Two groups of subjects were evaluated. The first participated in an educational program while the second had the educational program and in addition were supplied with a pedometer to assess their daily activities. The latter group was given specific goals to increase their activity level. The data is currently being analyzed.