Relationships Between Insomnia and Sleep-Disordered Breathing

Abstract

I read with interest the article by Krakow et al (December 2001)1Krakow B Melendrez D Ferreira E et al.Prevalence of insomnia symptoms in patients with sleep-disordered breathing.Chest. 2001; : 1923-1929Abstract Full Text Full Text PDF Scopus (208) Google Scholar on the prevalence of insomnia symptoms (ISs) in patients with sleep-disordered breathing (SDB). The study showed that insomnia complaints were common in SDB patients, but it remained unclear why some patients with repeated apneas had insomnia whereas others did not. I report here the prevalence of different subtypes of insomnia in SDB patients. The finding is useful in understanding the relationship between SDB and insomnia. I analyzed the data of 150 consecutive patients referred to our laboratory because of suspected obstructive sleep apnea (OSA).2Chung KF Use of Epworth Sleepiness Scale in Chinese patients with obstructive sleep apnea and normal hospital employees.J Psychosom Res. 2000; 49: 367-372Abstract Full Text Full Text PDF PubMed Scopus (102) Google Scholar ISs were reported using a Likert-scale to four statements: “difficulty getting to sleep” (IS-1); “wake up during the night and have a hard time getting back to sleep” (IS-2); “wake up repeatedly during the night” (IS-3); and “wake up too early in the morning and can't get back to sleep” (IS-4). Responses of “often” and “almost always” were considered presence of insomnia complaints. OSA according to the international classification of sleep disorders was diagnosed in 119 patients3Diagnostic Classification Steering Committee International classification of sleep disorders: diagnostic and coding manual. American Sleep Disorders Association, Rochester, MN1990Google Scholar who had an apnea-hypopnea index (AHI) ≥ 5 events per hour. The 119 subjects were predominately male (105 male and 14 female patients) and 44.6 ± 10.4 years of age (mean ± SD). The mean body mass index was 27.8 ± 5.0 and AHI was 37.3 ± 26.5. The most frequent IS was IS-3 (33%), followed by IS-4 (21%), IS-2 (16%), and IS-1 (9%). Subjects with and without ISs were similar in demographics, daytime sleepiness, and AHI. However, patients with difficulty initiating sleep (IS-1, IS-2, or IS-4) had significantly lower AHI (26.7 ± 24.6) than subjects with frequent awakenings (IS-3 only) [45.0 ± 26.1] and those with no insomnia (40.4 ± 26.3) [F = 4.5; degrees of freedom = 2, 116; p = 0.01]. The most common IS in SDB patients was frequent awakening, while a significant proportion of subjects had difficulty initiating sleep. It appears that repeated apnea is not the single factor that can account for the ISs in SDB patients, particularly in those with difficulty initiating sleep. Individual vulnerability to develop insomnia needs to be addressed.1Krakow B Melendrez D Ferreira E et al.Prevalence of insomnia symptoms in patients with sleep-disordered breathing.Chest. 2001; : 1923-1929Abstract Full Text Full Text PDF Scopus (208) Google Scholar4Ambrogetti A Olson LG Saunders NA Differences in the symptoms of men and women with obstructive sleep apnoea.Aust N Z J Med. 1991; 21: 863-866Crossref PubMed Scopus (82) Google Scholar5Pillar G Lavie P Psychiatric symptoms in sleep apnea syndrome: effects of gender and respiratory disturbance index.Chest. 1998; 114: 697-703Abstract Full Text Full Text PDF PubMed Scopus (162) Google Scholar Relationships Between Insomnia and Sleep-Disordered BreathingCHESTVol. 123Issue 1PreviewWe concur with Chung's conclusion, “Individual vulnerability to insomnia [in patients with sleep-disordered breathing (SDB)] needs to be addressed,” and our data also showed a statistically significant higher apnea-hypopnea index (AHI) in those without insomnia compared to those with insomnia.1 A tempting explanation, then, for SDB plus insomnia (“complex insomnia”2) in our sample would be their greater self-reported psychiatric distress and ruminations and anxiety about sleep1 in contrast to SDB-induced respiratory compromise and resultant sleep fragmentation. Full-Text PDF