Psychosocial and behavioural contributors to health: age-related increases in physical disability are reduced by physical fitness.

The aging process is associated with increased risk for disease which can cause physical and economic burden for older adults. In a national longitudinal sample of 3910 participants aged 24-75 years (55% women), we examined psychosocial and behavioural factors associated with physical health in adulthood. With hierarchical regression analyses controlling for Time 1 values of the dependent variable and demographic characteristics, we found that participants reporting better social relations, a higher sense of control, a smaller waist circumference and greater physical activity at Time 1 reported better self-rated physical health (Adj. R(2) = 0.33, F (11, 3661) = 164.66, p < 0.001) and less physical disability (Adj. R(2) = 0.44, F (13, 3659) = 226.25, p < 0.001) 9 years later than their counterparts reported. Furthermore, significant interactions showed that smaller waist circumference and greater physical activity at Time 1 attenuated age-related increases in physical disability. Beneficial effects of physical fitness are considered within the context of lifespan theories of health, and implications for interventions are discussed.