Effect of accumulated night work during the working lifetime, on subjective health and sleep in monozygotic twins

The present study sought to investigate the effects of lifetime accumulated night work on subjective health and sleep in monozygotic twins discordant on the exposure to night work. A total of 169 twin pairs (83 males, 86 females) over 65 years of age were analyzed on variables that describe the presence or absence of complaints regarding subjective health, disturbed sleep, repeated awakenings and not being well rested. Significant (P < 0.05) risk ratios (RR) were found for subjective health (RR = 1.67) and disturbed sleep (RR = 2.83) indicating a higher risk of developing complaints to former night workers. There was neither a dose-dependent effect of night work nor an interaction effect with gender observed.