Coexisting Insomnia and Sleep Apnea Lead to Fatal Outcomes

Bastien Lechat, MD

Based on recent research, investigators are urging for more research on the mechanisms involved with comorbid insomnia and obstructive sleep apnea (OSA) in order to reduce the mortality risk in patients with both conditions.

A team of investigators led by Bastien Lechat, MD, Adelaide Institute for Sleep Health and FHMRI Sleep Health, Flinders University, revealed the fatal implications linked to presence of these 2 common illnesses showing a need for more effective treatment options.

The symptoms of insomnia often occur alongside those of sleep apnea, and when both conditions are present the impact on sleep quality, daytime function, mental health, and quality of life is more severe compared with either condition on its own. This study aimed to evaluate these associations and their relationship with all-cause mortality.

The Relationship Between Sleep Disorders and Mortality

The data was gathered from the Wisconsin Sleep Cohort and included 1115 adult patients with an average age of 55 years and an almost equal representation of men (53%) and women. Investigators analyzed for potential associations between insomnia/sleep apnea and mortality and classified patients based on their symptoms: insomnia symptoms alone; OSA symptoms alone; both; neither.

The associations between the 4 patient categories and all-cause mortality were examined over a 20-year follow-up and analyzed with multivariable adjusted Cox regression models.

Defining symptoms of nocturnal insomnia were specified as: difficulties initiating, maintaining sleep, and/or early morning awakenings "often" or "almost always", and/or the regular use of sedative-hypnotic medicine. Obstructive sleep apnea was defined by an apnea-hypopnea index of 5 or more hours of sleep.

Comorbid Insomnia, Sleep Apnea and Mortality Risk

When comparing to the patient group with no symptoms of either disorder, there was no significant association of increased mortality risk, which was similarly observed with both insomnia alone and sleep apnea alone. However, a significant relationship was identified between coexisting insomnia/sleep apnea and an increased mortality risk.

Before conducting the analyses, investigators controlled for sociodemographic and behavioral factors.

More than half (52.2%) of the total patient population with insomnia symptoms had comorbid OSA. Of those with OSA, 36% also had insomnia symptoms. When compared with the control group, patients with both conditions and those with OSA alone had lower polysomnography total sleep time. There were no differences in total sleep time identified between the 3 sleep disorder groups.

Investigators found that anxiety and depression symptoms were increased among the patients with insomnia/sleep apnea and those with only insomnia symptoms when compared with the control group. Patients who had only OSA did not exhibit higher levels of anxiety and depression symptoms.

Findings also showed that cardiovascular disease was more prevalent among patients with both conditions, and also, to some extent in patients with OSA, but the pattern did not appear in those with insomnia alone. Similarly, the 2 groups also demonstrated a higher prevalence of hypertension.

The group with insomnia/sleep apnea had a higher crude mortality rate when compared with each of the other 3 groups. The group with insomnia alone had a crude mortality rate of 4.5 deaths per 1000, the group with sleep apnea alone had a rate of 5.2 deaths, and the control group had 4.0, which were all significantly lower than the rate of 9.5 deaths per 1000.

"The association between comorbid insomnia symptoms and OSA and mortality persisted after controlling for sociodemographic factors, behavioral factors, and chronic conditions, and remained quite consistent across multiple definitions of insomnia and OSA," investigators stated.

The study, "All-Cause Mortality in People with Co-Occurring Insomnia Symptoms and Sleep Apnea: Analysis of the Wisconsin Sleep Cohort" was published in Nature and Science of Sleep.