Polysomnography reveals unexpectedly high rates of organic sleep disorders in patients with prediagnosed primary insomnia.

OBJECTIVE: It is a matter of debate whether patients with primary insomnia require a polysomnographic examination in order to exclude specific sleep disorders such as sleep apnea syndrome (SAS) or periodic limb movements (PLM). Using a prospective design, we investigated the prevalence of organic sleep disorders by means of polysomnography (PSG) in a series of patients who were previously diagnosed with primary insomnia. This diagnosis was based on a clinical exam and an ambulatory monitoring device or previous PSG.
METHODS: Seventy-seven women and 16 men (mean age 55.12 ± 13.21 years) who were admitted for cognitive behavioral therapy for insomnia were evaluated by PSG including cardiorespiratory parameters and tibialis EMG. Among them, 50 patients had undergone a clinical exam by a sleep specialist; in 18 patients, actigraphy or portable monitoring had been performed to exclude SAS or PLM; 25 patients had undergone PSG in another sleep lab previously.
RESULTS: In 32 patients (34% of the sample), a PSG revealed a specific sleep disorder (SAS 16; PLMD 11; both 5), resulting in therapeutic consequences for 21 patients (SAS 10; PLMD 9; both 2). SAS and PLM patients were older and SAS patients had a higher body mass index than insomnia patients without additional findings.
CONCLUSION: Indications for a PSG should be handled less restrictively in the diagnostic workup of older insomnia patients since they have a higher risk of comorbid sleep disorders even in the absence of the clinical signs of SAS or PLM.