Sleep duration in midlife and old age and risk of mortality over a 48-year follow-up: The Helsinki businessmen study (HBS) cohort

•Sleep duration in midlife and old age was related to all-cause mortality.•Mortality with short sleep duration in midlife was attributed to unhealthy lifestyle factors.•In old age long but not short sleep duration was associated with mortality. Both short and long sleep duration have been associated with increased mortality, but there are few truly long-term studies. This is a cohort study of 2504 men born between 1919 and 1934. In 1974–1975 (mean age 48), participants underwent baseline clinical examinations and sleep duration assessments. A follow-up examination took place 35 years later, in 2010 (mean age 82). All-cause mortality data from baseline and from old age were collected through to December 31, 2022. At baseline, short sleep duration (≤6 h per night), normal sleep duration (>6 and ≤ 8 h), and long sleep duration (>8 h) was reported by 266, 2019 and 219 men, respectively. Men with short sleep duration had higher levels of smoking, alcohol consumption, body mass index, and poorer self-rated health than those with normal sleep duration. During the 48-year follow-up, 2287 men died. The unadjusted hazard ratio for mortality was 1.20 (95 % confidence interval [CI] 1.05–1.37) for short compared with normal sleep duration, but this association vanished after adjustments (1.01, 95 % CI 0.87–1.17). In old age, the corresponding hazard ratios were 1.41 (1.16–1.72) and 1.19 (0.94–1.51) for short sleep duration and 1.33 (1.09–1.63) and 1.31 (1.02–1.67) for long sleep duration. In a comprehensive lifespan follow-up, the modestly increased mortality among men with short sleep duration in midlife was attributed to unhealthy lifestyle factors. In old age both long and short sleep duration seemed to be associated with modestly increased mortality. ClinicalTrials.gov identifier for the HBS: NCT02526082