Insomnia symptoms linked to increased mortality

By Joanna Lyford, Senior medwireNews Reporter

Certain aspects of insomnia are associated with an increased risk for mortality, shows an analysis of a large cohort of US men.

Among participants in the Health Professionals Follow-up Study, difficulties falling asleep and having nonrestorative sleep were associated with an increased risk for all-cause and cardiovascular mortality.

“[I]nsomnia symptoms may be an important modifiable risk factor affecting longevity,” write Xiang Gao (Harvard Medical School, Boston, Massachusetts, USA) and co-authors in Circulation.

In a two-part study, Gao et al first assessed mortality among 23,447 US men aged 40-75 years who were free of cancer at baseline and were followed up for 6 years. During this time, 2025 men died.

The baseline prevalence of insomnia symptoms was 4.1% for difficulty initiating sleep, 25.2% for difficulty maintaining sleep, 7.7% for early-morning awakening, 6.2% for nonrestorative sleep, and 11.1% for excessive daytime sleepiness.

After adjusting for potential confounders, men who regularly experienced three insomnia symptoms – difficulty initiating sleep, nonrestorative sleep, and daytime sleepiness – were associated with an increased risk for all-cause mortality, at hazard ratios (HRs) of 1.25, 1.24, and 1.24, respectively, compared with people without these symptoms.

Interestingly, these risks were additive, so the highest risk for total mortality was in men with multiple insomnia symptoms.

The symptoms of difficulty initiating sleep and daytime sleepiness were also associated with an increased risk for cardiovascular mortality, at HRs of 1.55 and 1.32, respectively.

To confirm their findings, Gao et al pooled these new data with those from nine other published studies. This gave HRs for total mortality of 1.14 and 1.17 for difficulty initiating sleep and nonrestorative sleep, respectively. The results were unchanged after excluding poor-quality studies and in a sensitivity analysis that excluded participants with major comorbidities at baseline.

The researchers note that normal sleep continuity is important for the maintenance of cardiovascular, metabolic, and immune function, and that suboptimal sleep disturbs both circadian rhythms and other physiologic systems.

They write: “Future research in this field is warranted, especially the long-term epidemiological studies about the association between individual insomnia symptoms and mortality, and experimental and clinical studies probing mechanisms underlying the insomnia-mortality associations.”

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