By Barbara A. Phillips, MD, MSPH,
Professor of Medicine, University of Kentucky; Director, Sleep Disorders Center, Samaritan Hospital, Lexington.
Synopsis: A limited pilot study determines most of the awakenings reported in insomnia patients were symptomatic of other sleep-disorders’ respiratory events.
Source: Krakow B, et al. Prospective assessment of nocturnal awakenings in a case series of treatment-seeking chronic insomnia patients: A pilot study of subjective and objective causes. Sleep 2012;35:1685-1692.
To ascertain what leads insomnia patients to wake up at night, the authors of this study took patients from the Maimonides Sleep Arts and Sciences who had no prior experience with sleep studies. Candidates for inclusion needed to be adults, have insomnia listed as their primary sleep problem, have reached a threshold of 15 on the Insomnia Severity Index, speak fluent English, and have completed an internet survey. In addition to several surveys regarding their sleep habits, patients answered related questionnaires regarding depression and insomnia. Throughout the nearly two years of amassing data, only 20 of the initial 512 insomnia patients met all of the qualification criteria to complete the study. Each patient was subject to comprehensive evaluations that included polysomnograms and physical examinations, as well as pre-sleep and follow-up interviews. Of the 20 patients, each reported experiencing difficulty sleeping; however, 17 also reported difficulty in falling asleep apart from staying asleep. Following the trend of many insomnia patients, self-reported quality of sleep was much lower than the test results displayed. For example, the patients estimated that on average they slept about 5 hours during laboratory monitoring, when in actuality their average was 6 hours. Many of the patients also drastically overestimated the time they took nightly to fall asleep, and the average time they spent awake after first falling asleep for the night. Stress and worries were gleaned from interviews as the primary causes for both difficulties falling and staying asleep. After psychological factors, nocturia (excess urination during the night) and nightly pain were the next most common reasons given for sleep difficulty. None of the 20 patients reported that their sleep difficulties were caused by breathing difficulty.
Analysis of the sleep study’s objective measures identified the primary cause of wakening as respiratory events. Nearly 90% of the 531 (around 27 per patient studied) awakenings registered during the study were identified as caused by such. The average time duration of the awakenings triggered by respiratory events was 25 minutes. Moreover, the frequency of respiratory events experienced strongly correlated with each reported Insomnia Severity Index score. Over half of the patients in the study met the standard criteria for sleep apnea, while each of the others were diagnosed with upper-airways resistance syndrome. Secondary analysis and evaluation determined that though the majority of awakenings were instigated by respiratory events, very few of the respiratory events experienced actually led to awakenings.
At the conclusion of the testing period, 85% of the patients indicated that they would accept that their sleeping difficulty was affected by sleep disordered breathing (SDB). Of the patients, 12 even took the initiative to undergo SDB treatment. The results of these treatments are as of yet unknown. Nonetheless, the pilot study shows that in at least a select group of patients, self-reported insomnia is often symptomatic of undiagnosed sleep-disordered breathing.