Habitual physical activity and health-related quality of life in older adults: interactions between the amount and intensity of activity (the Nakanojo Study)

Abstract

Purpose: This study examined relationships between health-related quality of life (HRQOL) and objective assessments of habitual physical activity in older adults, focusing on interactions between the amount and intensity of activity.

Methods: Subjects were healthy Japanese aged 65-85 years (74 men and 109 women). Pedometer/accelerometers measured their step counts and the intensity of physical activity in metabolic equivalents (METs) continuously 24 h per day for 1 year. Each individual's final HRQOL was assessed using the Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36) instrument.

Results: The daily step count and the daily duration of physical activity at an intensity >3 METs were quite closely correlated (quadratic r2 = 0.93, P < 0.05). After controlling for age, sex, and daily step count, the overall SF-36 score and four constituent dimensions (physical functioning, freedom from pain, vitality, and mental health) were all significantly higher in individuals spending >25% of their total activity at an intensity >3 METs. However, engagement in activity >3 METs was not significantly associated with the remaining SF-36 components (physical limitations, general health, social functioning, and emotional limitations).

Conclusions: Associations between moderate-intensity physical activity and HRQOL in older adults merit further evaluation by prospective studies and/or randomized controlled trials.