Gender and ethnic differences in prevalence of self-reported insomnia among patients with obstructive sleep apnea.

BACKGROUND: Insomnia and obstructive sleep apnea (OSA) are the two most common sleep disorders. Studies have shown that complaints of insomnia are prevalent among sleep clinic patients evaluated for OSA. Less is known about the gender and ethnic variations in this association.

OBJECTIVES: This paper aims to study the influence of gender and ethnicity in the prevalence of insomnia in patients with OSA and explore the association between these two disorders with an emphasis on psychophysiologic insomnia.

METHODS AND MEASUREMENTS: We reviewed case files, including self-reported questionnaires and polysomnography studies of 300 OSA patients [apnea-hypopnea index (AHI) of >10] from three ethnic groups--Caucasian, Hispanic, and African American, 50 patients each, male and female, seen at a tertiary care county hospital adult sleep center. Self-reported insomnia was classified as sleep onset insomnia, sleep maintenance insomnia, or insomnia with early morning awakening. Psychophysiologic insomnia was documented if the patient reported two of the following five symptoms: racing thoughts when trying to sleep, increased muscle tension when trying to sleep, fear of being unable to sleep, fear of being unable to fall back to sleep after waking up, and lying in bed worrying. Fischer exact tests for each contingency table were run using SPSS.

RESULTS: Among OSA patients, women were older, had higher body mass index, and lower AHI at the time of diagnosis, compared to men. Insomnia was more prevalent among patients with OSA (84%) than the reported 30% among general adult population. Sleep onset insomnia was reported more frequently by women (62%) than men (53%) (p = 0.03). Similarly self-reported psychophysiologic insomnia also showed a female preponderance (53% vs. 45%, p = 0.03). Caucasian women had the highest rate of self-reported sleep maintenance insomnia (80%). Hispanic women are more likely to complain of symptoms suggestive of psychophysiologic insomnia (58%).

CONCLUSIONS: There is a higher prevalence of insomnia in OSA patients. Ethnicity and gender possibly exhibit a complex and significant influence on the reported subtype of insomnia. Further larger studies may help confirm, as well as clarify, mechanisms that underlie the ethnic and gender differences that we have noted.