Patterns of 12-year change in physical activity levels in community-dwelling older women: can modest levels of physical activity help older women live longer?

Abstract

Few studies have addressed changes in physical activity participation over time among the elderly. The authors hypothesized that there were distinct trajectories of physical activity level over time and identifiable predictors of such trajectories, as well as that the maintenance of regular physical activity, even below recommended levels, was associated with lower mortality risk. Using longitudinal data (1994-2009) from 433 initially high-functioning older women aged 70-79 years at baseline, a joint latent class and survival mixture model identified 4 activity trajectory classes: always active (16.6%), fast declining (19.2%), stable moderate (32.3%), and always sedentary (31.9%). Obesity, coronary artery disease, chronic obstructive pulmonary disease, depressive symptoms, low self-efficacy, mobility disability, and low energy were associated with sedentary behavior and/or a fast decline in activity. Women in the fast declining and always sedentary classes had hazard ratios for death of 2.34 (95% confidence interval: 1.20, 4.59) and 3.34 (95% confidence interval: 1.72, 6.47), respectively, compared with the always active class; no mortality difference was found between the stable moderate and always active groups (hazard ratio = 1.24, 95% confidence interval: 0.63, 2.47). Our findings suggest that physical activity does not have to be vigorous to be beneficial and that the gain may be the greatest among women who reported the lowest levels of activity.

Figures

Figure 1.

Relation between National Health Interview Survey (NHIS) physical activity level at baseline and 10-year all-cause mortality rate adjusted for age, race, and educational level among women in the Women's Health and Aging Study II (1994–2009) who reported any activity at baseline (n = 401). Shown are relative hazard estimates for mortality linked to specific activity levels compared with the hazard linked to the Centers for Disease Control and Prevention/American College of Sports Medicine recommended 150 minutes of moderate-intensity physical activity per week (equivalent to approximately 1,000 kcal/week for an individual weighing 60 kg or 2.38 kcal/day/kg, as denoted by the vertical dashed line). The curve represents the age-, race-, and educational level-adjusted relative mortality hazards across activity levels, and the bars indicate their 95% confidence intervals. The y-axis was transformed so that, for example, the graphic display of an increase in risk of the magnitude of 2 (hazard ratio = 2) would be equivalent to that of a decrease in risk of the same magnitude (hazard ratio = 0.5) in terms of scale size.

Figure 2.

A) Prevalence of being very active (white), moderately active (grey), and inactive (black) by the National Health Interview Survey criteria over time in the Women's Health and Aging Study II, 1994–2009. B) Average minutes per week of physical activity participation by activity type and follow-up time (year) in the Women's Health and Aging Study II, 1994–2009.

Figure 3.

Results from the mixture survival model: estimated prevalence of being very active by the National Health Interview Survey criteria within each of the 4 physical activity trajectory classes, the Women's Health and Aging Study II, 1994–2009.

Figure 4.

Kaplan-Meier survival curve by physical activity trajectory classes in the Women's Health and Aging Study II, 1994–2009. Shown are curves for the always active (dot-dashed line, squares), fast declining (dashed line, circles), stable moderate (solid line, triangles), and always sedentary (dotted line, cross) groups, with the squares, circles, triangles, and crosses representing censoring time within each of the 4 classes, respectively.