Insufficient sleep - A population-based study in adults

Study objectives: Insufficient sleep (sleep deprivation) is a common proble m of considerable health, social, and economical impact. We assessed its pr evalence and associations, and the role of genetic influences. Design: Panel study based on questionnaires administered in 1981 and 1990. Setting/Patients: 12.423 subjects aged 33-60 years included in the Finnish Twin Cohort, representative of the Finnish population. Interventions: N/A Measurements: A difference of 1 hour between the self-reports of the sleep need and the sleep length was considered insufficient sleep. Associations w ith education, life style, work, psychological characteristics and sleep-wa ke variables were assessed. Structural equation modelling techniques were u sed to compare genetic models among monozygotic and dizygotic twin pairs. Results: In 1990, the prevalence of insufficient sleep was 20.4% (16.2% in men and 23.9% in women). 44% of those with insufficient sleep in 1981 also had it 9 years later (Spearman correlation for persistence 0.334). In multi variate analyses, the strongest positively associated factors were daytime sleepiness (women: odds ratio 3.87, 95% confidence limits 3.24-4.63/men: 3. 77,2.98-4.75), insomnia (2.48,1.92-3.1912.91,2.17-3.90), not able to sleep without disturbance (1.95,1.47-2.60/2.54,1.66-3.89), and evening type (2.10 ,1.65-2.69/1.73,1.25-2.41). Among men, also weekly working hours greater th an or equal to 75 was strongly associated (3.23,1.54-6.78). "Not working" w as negatively associated in both genders (0.68,0.51-0.89/0.59,0.42-0.83). T wo thirds of the interindividual variability in the liability to insufficie nt sleep was attributed to non-genetic factors. Conclusions: Insufficient sleep is a common and long-standing condition, mo st strongly associated with sleep/wake variables. One third of the liabilit y to it is attributed to genetic influences. Sleep sufficiency should be as sesssed in health examinations of working adults.