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

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. 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. The daily step count and the daily duration of physical activity at an intensity > 3 METs were quite closely correlated (quadratic r (2) = 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). Associations between moderate-intensity physical activity and HRQOL in older adults merit further evaluation by prospective studies and/or randomized controlled trials.