Midlife work demands and all-cause mortality: Do lifestyle factors modify the association?

Abstract Background The effect of occupational exposures on the risk of death may depend on the existence of unhealthy lifestyles. The confounding role of lifestyle factors within this association has often been analyzed, yet studies on the interaction between job demands and lifestyle factors are limited. We aim to evaluate the combined effect of midlife work demands and lifestyle factors on all-cause mortality in later life on multiplicative and additive scales. Methods We investigated 6234 middle-aged individuals who reported their exposure to physical and psychosocial work demands in the Finnish Longitudinal Study of Aging Municipal Workers at baseline in 1981. We collected their linked mortality data until the year 2010 from the Finnish National Population Register. The lifestyle factors included smoking, alcohol drinking, and physical activity. By fitting a Weibull distribution and adjusting for socio-demographic variables, we measured the mortality risks associated with both work demands separately, in the presence or absence of each lifestyle factor. Results The mortality risk associated with joint exposure to high physical demands and unhealthy lifestyles was higher than that associated with either exposure alone. The adjusted hazard ratio for the combined exposure to physically heavy work and leisure-time physical inactivity was 1.34 (95% CI 1.01-1.78), whereas the corresponding risks for the single exposures were 0.97 (95% CI 0.78-1.20) and 1.26 (95% CI 0.84-1.88), respectively. Having both high psychosocial demands and poor health behaviors was linked to a higher risk of death, though the risks in the singly exposed groups may still be greater, depending on the specific behavior. In both work demands, there were signs of positive interactions on both scales. Conclusions Our study shows that the all-cause mortality risk among individuals with both high physical demands and unhealthy lifestyles is higher than that among those with only one of the exposures. Key messages • The negative impact of physical work demands on survival in older age may depend on the presence of unhealthy lifestyles. • People in manual occupations who also adopt unhealthy lifestyles may face a higher risk of death as they age than their peers with either manual jobs or poor health behaviors alone.