PITTSBURGH—Serious mental illness increases the likelihood of sleep apnea by 26%, according to researchers at the VA Pittsburgh Healthcare System.

Their study, recently published in Psychosomatics, also found that nearly 9% of all veterans had sleep apnea. At the same time, 1 in 7 veterans with serious mental illness, defined in the study as bipolar disorder, schizophrenia and schizoaffective disorder, had a diagnosis of sleep apnea.1

“The high rate might be explained by patients with serious mental illness having a high rate of factors that increase risk of sleep apnea, such as obesity, hypertension, smoking and diabetes,” said lead author Isabella Soreca, MD, director of sleep medicine/behavioral health at the Pittsburgh VA. “That’s one obvious cause, but we don’t really know. It could also be that medications prescribed for these mental illnesses affect breathing control and central respiration.”

While the 13.7% rate of sleep apnea in veterans with serious mental illness in the study is quite high, the real rate could be higher still.

“That’s likely not the true prevalence,” Soreca told U.S. Medicine. “It’s probably still a significant underestimate, because there isn’t a process in place for systematic screening for sleep apnea.”

Multiple factors contribute to underdiagnosis beyond lack of screening, she explained.

“Sleep apnea has been underdiagnosed broadly, not just in those with serious mental illness, in part because it used to require referral to a sleep lab, which limited access,” Soreca told U.S. Medicine.

The higher prevalence of sleep apnea in all veterans seen in this study compared to previous research likely resulted from the increased use of portable home testing technology for diagnosing sleep apnea after 2000 as well as increased awareness of the sleep disorder among clinicians in recent years, she noted.

Even with home testing, underdiagnosis of sleep apnea remains a problem. “Those diagnosed in the study were veterans who were referred to sleep medicine and who made it to an appointment for evaluation. For patients with serious mental illness, social instability, financial issues and transportation can create additional barriers to diagnosis,” Soreca said.

The Pittsburgh team analyzed a dataset of 33,818 veterans who had a primary care visit in 2007, then looked for diagnoses of mental illness and sleep apnea in that cohort from 2001 up to 2011.

In VISN 4, 6.2% of veterans had a diagnosis of bipolar disorder, schizophrenia and schizoaffective disorder, the cluster of serious mental illness analyzed in this study. “Nationally, VA data says that up to 12% of veterans have a serious mental illness when you include post-traumatic stress disorder and major depressive disorder,” Soreca added. Previous studies have shown markedly elevated prevalence of sleep apnea among veterans with both of those conditions.

Overlapping Risk Factors

The researchers noted another reason that sleep apnea goes undiagnosed in many veterans with serious mental illness.

“Sleep apnea and SMI can share clinical features, which may mask sleep apnea. For example, daytime sleepiness and poor cognitive performance due to sleep apnea may be attributed to negative symptoms of SMI, such as apathy and cognitive slowing, or medication side effects, even if sleep apnea is present,” they wrote.

As a result, even common indicators of sleep apnea are often overlooked. “The very same cluster of symptoms that would prompt a sleep evaluation in the general population is not readily recognized in patients with SMI,” the authors said.

Veterans with serious mental illness developed sleep apnea at a younger age than other veterans. Two out of 5 veterans with sleep apnea and SMI were under age 50, compared to 28.4% of those without serious mental illness.

Those with sleep apnea and SMI also had a significantly higher average number of chronic medical comorbidities (10.19), despite a younger mean age, than those with SMI and no apnea (8.16) or sleep apnea without SMI (9.45).

While increasing clinician awareness of the high prevalence on sleep apnea in this population is critical to improving the rate of diagnosis, overcoming other provider and patient issues is also important. Clinicians might be uncomfortable with patients who have severe psychiatric illness or could have concerns about coordination of care or the ability of these patients to adhere to treatment recommendations, the authors said.

Patients with serious mental illness pose some unique issues for treating sleep apnea, too. “Cognitive deficits are often associated with serious mental illness,” Soreca noted. “Patients may have slower reaction times, less cognitive flexibility, and take longer to understand instructions.”

Those challenges can be overcome by tailoring education and monitoring veterans with serious mental illness more closely, however. “Instructions need to be simple, with clear writing and maybe pictorial clues so they don’t have to remember everything on the first run with new equipment. Frequent check-ins and troubleshooting to improve adherence could also help,” she added.

Diagnosing sleep apnea in veterans with SMI ultimately comes down to considering that they may have sleep apnea, as well, and that treatment could help.

“We want clinicians to think about referring patients to sleep medicine whenever they encounter difficult-to-treat symptoms of depression, excessive sleepiness and overweight,” said Soreca. “Even if other factors might explain it, sleep apnea could still be a major contributor to the problems.”

1 Soreca I, Tighe CA, Bramoweth AD. The Intersection of Sleep Apnea and Severe Mental Illness in Veterans. Psychosomatics. 2019 Jan 22. pii: S0033-3182(19)30022-2.