Stress and sleep : prevalence, vulnerability and day-to-day variation

Abstract

Stress and sleep problems are increasingly common in society with consequences not only for individual health, but also high societal costs. The focus of this thesis is how sleep is affected by day-to-day variation in naturally occurring stress, the impact of individual vulnerability to stress-related sleep disturbances and the causes people attribute their disturbed sleep to. This was investigated through polysomnographically (PSG) recorded sleep in home-settings during periods of different levels of work stress, sleep diaries over extended periods and a population-based survey on prevalence and association of stress and disturbed sleep.

The results suggest that moderate intensity, short-term stress has a limited negative impact on sleep, in terms of a decreased sleep efficiency and self-rated non-restorative sleep. However, the response was stronger in individuals with a pre-existing trait of vulnerability to stress induced sleep disturbances, resulting in a more fragmented sleep and decreased duration of rapid eye movement (REM) sleep. Although the day-to-day variation in sleep quality appeared to be quite sensitive to small variations in stress level, a key factor seemed to be the presence of stressful thoughts and worries at bedtime. The weekend appeared to serve as a possibility to compensate the sleep impairment of the workweek, as sleep duration was extended and the amount of slow wave sleep (SWS) increased. In chronically stressed individuals in the general population however, sleep duration was not compensated, instead a reduction was seen for both weekdays and weekend, suggesting an impaired recovery ability related to a high frequency of stress. The general population, particularly the women and persons in the younger age-groups, most commonly attributed their sleep problems to stress. The highest prevalence of stress was seen in the 35-44 age group, while the peak for prevalence of stress disturbed sleep occurred a little later, in the age 45-54 years. It was concluded that the most common attribution of poor sleep is stress, and that everyday stress had a negative effect on polysomnography, but at a rather modest level, although the effect was larger on those reporting a pre-existing sleep sensitivity to stress.