The mortality risk of night-time and daytime insomnia symptoms in an older population

The current study examined the association between insomnia symptoms and all-cause mortality in older adults (≥ 65 years). Data was used from 1969 older adults [M = 78 years, SD = 6.7 years] who participated in the Australian Longitudinal Study of Ageing. Insomnia symptoms were defined by nocturnal symptoms (difficulty falling asleep, difficulty maintaining sleep, early morning awakenings) and daytime symptoms (concentration difficulties, effort, inability to get going). Frequency of symptoms were combined to calculate an insomnia symptom score ranging from 0 (no symptoms) to 24 (sever symptoms) and quintiles of the score were constructed to provide a range of symptom severity. Multivariable Cox models were conducted to assess associations between insomnia symptom severity and mortality risk. In the median follow up of 9.2 years, there were 17,403 person-years at risk and the mortality rate was 8-per 100 person-years. Insomnia symptom severity was associated with increased mortality in the most severe quintile (adjusted HR_Q1vsQ5 = 1.26, 95%CI [1.03-1.53], p = .02). Subsequent analyses showed this association was driven by daytime symptoms (adjusted HR_Q1vsQ5 = 1.66, [1.39-2.00], p < .0001), since nocturnal symptoms alone were not associated with increased mortality (adjusted HR _Q1vsQ5 = 0.89, [0.72-1.10], p = .28). Findings suggest daytime symptoms drive increased mortality risk associated with insomnia symptoms. Findings may be therapeutically helpful by reassuring individuals with nocturnal insomnia symptoms alone that their longevity is unlikely to be impacted.