Insomnia in Shift Work Disorder Relates to Occupational and Neurophysiological Impairment

Feb 11, 2015Journal of clinical sleep medicine : JCSM : official publication of the American Academy of Sleep Medicine

Insomnia in shift work disorder is linked to work problems and brain function issues

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Abstract

The alert insomniac group displayed a 25.8% impairment on the work productivity scale compared to controls.

Alert insomniacs experienced significantly greater work productivity impairment than controls, while sleepy insomniacs did not show a statistically significant difference.
Cognitive responses measured by brain activity showed that alert insomniacs had reduced brain response to auditory targets compared to controls.
There was no significant difference in cognitive responses between sleepy insomniacs and controls except at one electrode site.
Insomnia severity measurements correlated with work productivity and attention-related brain response, indicating a potential link between insomnia and cognitive function.
No correlation was found between sleep latency or sleepiness scores and work productivity or cognitive response measurements.

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STUDY OBJECTIVES: To determine whether occupational and neurophysiological decrements within shift work disorder (SWD) are differentially related to its two diagnostic symptoms, insomnia and excessive sleepiness.

METHODS: Thirty-four permanent night workers participated in an overnight lab protocol including a multiple sleep latency test (MSLT) and an event-related brain potential (ERP) task testing auditory target detection (P3a and P3b). At 16:00, each subject completed an Endicott Work Productivity Scale (EWPS), two Insomnia Severity Indices (ISI-Day, ISI-Night), and an Epworth Sleepiness Scale (ESS). Subjects were grouped by ISI and ESS scores into clinical phenotypes. This study compared EWPS and ERP results between alert insomniacs ("AI," reporting insomnia without sleepiness), sleepy insomniacs ("SI," reporting both insomnia and sleepiness), and controls.

RESULTS: The AI group was most impaired on the EWPS, significantly more impaired than controls (25.8 ± 14.8 vs. 12.3 ± 9.4, p < 0.05). SI were not statistically different from controls (19.5 ± 8.7 vs. 12.3 ± 9.4, p > 0.05). Compared to controls, AI showed significantly attenuated P3a response (Fcz, Czp, Cpz, mean difference [MD] 1.62-1.77, p < 0.05) and target-detection P3b response (Fcz, Czp, Cpz, MD 1.28-1.64, p < 0.05). P3b in SI was not different from controls (p > 0.10), and P3a was only different at one electrode site (Cpz, MD 1.43, p < 0.01). Neither the MSLT nor the ESS correlated with EWPS scores or ERP (P3a/P3b) amplitudes (p > 0.10). However, the mean of the ISI measurements correlated with the EWPS (r = 0.409, p < 0.01) and the attention-to-novelty P3a (r = -0.410, p < 0.01).

CONCLUSIONS: Among shift work disorder patients, insomnia is linked to functional and cognitive impairments. Insomniacs with normal sleepiness showed more severe impairments than insomniacs who also reported excessive sleepiness.

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Insomnia in Shift Work Disorder Relates to Occupational and Neurophysiological Impairment

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