Sleep apnea plus insomnia tripled mortality risk in a six-year cohort of 2,401 patients

Between 30% and 50% of people with obstructive sleep apnea also have insomnia, a combination researchers call COMISA. A prospective cohort study published this month in the Journal of Clinical Sleep Medicine followed 2,401 patients from a hospital sleep clinic for six years to measure how that combination affects survival [s1].

The design

Between January 2016 and December 2018, 2,401 patients with suspected obstructive sleep apnea underwent standard respiratory polygraphy — an at-home or in-clinic test measuring breathing during sleep — and were enrolled in the analysis [s1]. Sleep apnea severity was categorized by the respiratory event index (REI); insomnia was assessed using the Bergen Insomnia Scale [s1]. All-cause mortality was tracked as the primary endpoint over six years of follow-up [s1]. The cohort had a mean age of 49.6 years and was 68.8% male; 36.2% had sleep apnea with REI ≥15 (moderate-to-severe), 49.5% had insomnia, and 16.9% had COMISA — the combination of insomnia and moderate-to-severe sleep apnea [s1].

What it found

Mortality risk rose progressively with sleep apnea severity across the study's REI categories [s1]. In a multivariable Cox regression analysis adjusting for other factors, moderate-to-severe sleep apnea (REI ≥15) alone was independently associated with more than double the risk of all-cause mortality: hazard ratio 2.65 (95% CI 1.12–6.30, p = 0.027) [s1]. When COMISA — the combination of insomnia and moderate-to-severe sleep apnea — was substituted into the same statistical model in place of sleep apnea alone, the relative risk rose further, to roughly threefold: hazard ratio 3.02 (95% CI 1.30–7.04, p = 0.010) [s1].

Reading the confidence intervals

Both hazard ratios carry fairly wide confidence intervals — the sleep apnea estimate spans from 1.12 to 6.30, and the COMISA estimate from 1.30 to 7.04 — which reflects the number of death events the analysis had to work with in a cohort of this size over six years; the study's summary does not report the total death count directly, which limits how precisely the estimates' reliability can be judged from the abstract alone. Both intervals stay above 1.0, meaning even at their lower bound, the associations remain statistically significant, but the true effect size could plausibly be considerably larger or smaller than the point estimates of 2.65 and 3.02 suggest.

What this adds to what's already known

The finding that sleep apnea severity predicts mortality is not new — it's been documented, if inconsistently, across prior studies, which the paper's authors note have been "inconclusive" [s1]. What this cohort adds is a direct, same-model comparison showing that adding comorbid insomnia to the same patients increases the mortality signal further, rather than simply representing two independent risk factors that happen to co-occur. That's the basis for the authors' argument that COMISA should be recognized as its own distinct, higher-risk phenotype in clinical practice, rather than sleep apnea and insomnia being assessed and treated as separate, unrelated conditions in the same patient [s1].

What this doesn't establish

This is an observational cohort from a single hospital sleep clinic, not a randomized trial, so it can show association between COMISA and mortality but cannot by itself prove that insomnia causally amplifies sleep apnea's mortality risk rather than reflecting some other shared underlying vulnerability — general poor health, more severe symptoms overall, or unmeasured confounders. The cohort recruited people already referred for suspected sleep apnea at a hospital sleep clinic, which may not represent sleep apnea as it exists in the broader population, particularly people who are undiagnosed or never referred for testing. Cause of death is not broken down in the available summary — the study measures all-cause mortality, not deaths specifically attributable to cardiovascular or respiratory causes.

What to watch

Whether treating insomnia specifically, alongside standard sleep apnea treatment like CPAP, in COMISA patients measurably reduces this excess mortality risk — a question this observational cohort cannot answer and that would require an interventional trial. This article is not medical advice.

Sources

1. Impact of obstructive sleep apnea and comorbid insomnia on all-cause mortality: a prospective cohort study of 2401 patients with 6-year follow-up — Journal of Clinical Sleep Medicine, 8 April 2026