Sleep quality and daytime functioning in primary insomnia: a prospective study
2014-09-03T09:29:55Z (GMT) by
In a 9-month prospective study, sleep and daytime functioning were compared in a community sample of 86 participants aged 25-50 years: 43 meeting DSM IV criteria for primary insomnia (26 women & 17 men); and 43 controls (32 women & 11 men). Assessments were conducted at baseline, 4 and 8 months, and included: the Pittsburgh Sleep Quality Index; Spielberger StatefTrait Anxiety Inventory; Eysenck Personality Questionnaire, Beck Depression Inventory; Fatigue Severity Scale; SF-36; Epworth Sleepiness Scale; Dysfunctional Beliefs About Sleep Scale; Sleep Hygiene and Practices Scale, Sleep Disturbance Questionnaire and the Psychomotor Vigilance Task PVT. An instrument to assess the occupational consequences of insomnia (the Occupational Impact of Sleep Questionnaire; OISQ) was also developed in the course of the study. PWI versus control group comparisons were made with repeated measures multivariate ANOVAs. Differences were consistently and significantly maintained on measures of state (F = 15.85 P <0.001) and trait anxiety (F = 23.46; P < 0.001), depression (F = 18.37; P < 0.001), fatigue (F = 22.20; P < 0.001), and neuroticism (F = 11.09; P < 0.001). Among PWI, mental health (F = 14.04; P < 0.001), pain (F = 6.92; P < 0.001), role-emotion (F = 10.94; p < 0.001), general health perceptions (F = 4.77; P < 0.05), social functioning (F = 6.58; P < 0.01) and energy and vitality (F = 32.08; P < 0.001), on the SF-36, were consistent with inferior health related QoL. In addition, pre-sleep arousal (F = 14.76; P < 0.001), sleep hygiene (F = 35.26; P < 0.001) and sleep disturbance (F = 72.32; P < 0.001) were significantly worse within PWI. Subjectively reported TIB (F = 9.38; P < 0.01), SOL (F = 11.17; P < 0.01) and WASO (F = 21.10; P < 0.001), remained greater within PWI, with SE (F = 15.29; P < 0.001), TST (F = 9.38; P < 0.01) and subjective sleep quality (F = 29.57; P < 0.001) greater within controls.Data averaged over the duration of data collection (252 days) found PWI reported an average SOL >30 minutes, an average WASO of> 30 minutes, SE < 80%. Analysed in terms of night to night sleep quality, both PWI and controls showed a pattern of 'good' (sleep efficiency >80%) and 'poor' (sleep efficiency <80%) nights. However, the probability of individual poor nights remained consistently and significantly higher for PWI across the 9 months of the study. Actigraphy data failed to confirm between group differences in sleep, and correlation with diary measures was low in both groups. PVf performance showed instability. Significant group differences found at baseline, were no longer present at subsequent data collection points. Data support the inconsistency surrounding objective performance among PWI within the literature. However, the inconsistency can be attributed to greater change within control participant's performance, rather than within PWI. Data identified the existence of a stable subgroup of PWI reporting symptoms of daytime sleepiness. Daytime sleepiness was found to be a temporally stable feature for this sub-group of PWI, who also Showed a distinctive psychological profile compared to PWI who did not report daytime sleepiness. No difference, however, was observed in subjectively reported sleep structure, quality or daytime performance between these subgroups of PWI. Insomnia subgroup analyses suggest a trait-like difference between sleepy and non sleepy PWI.The OISO showed an acceptable level of internal consistency reliability (alpha 0.93); and successfully discriminated between PWI and controls. The OISO also showed consistent correlations with measures of global sleep quality and subjective sleep parameters. Expressed in terms of comparative percentage decrement, PWI showed a consistent 10% decrement in subjective occupational performance when compared with controls. The OISO shows that absenteeism and punctuality may not capture the full impact of insomnia on workplace performance.