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by Maurice Ohayon In the past twenty years, over 20 epidemiological surveys assessing insomnia in the general population have been published. However, the definition of insomnia symptoms varies considerably across these studies, as do the time frame and the wording of questions. Most investigations define insomnia symptoms differently. Few specifically address the daytime consequences or distress accompanying insomnia symptomatology. The mental health status of insomnia complainers had rarely been explored, despite the fact that it is the most frequently associated factor with insomnia observed in sleep clinics. This research into insomnia symptomatology has established that sleep complaints are common in the general population and affect primarily women and the elderly. Epidemiologists must now distinguish between the various subtypes of insomnia. Few surveys present insomnia complaints as a whole when assessing their causes and consequences. Moreover, epidemiological data on transient and seasonal patterns of insomnia are non-existent. Longitudinal epidemiological data on the evolution and consequences of insomnia complaints are still lacking. To date, only two surveys have addressed this specific subject in the general population. The epidemiology of sleep disorders is still a fledgling discipline encompassing a broad range of phenomena. Surveys in the field remain scarce and existing figures are difficult to compare owing primarily to the considerable shift undergone by sleep disorder classifications over the years. This in itself may account in large part for the wide variance in prevalence rates between the earliest and the most recent studies. Methodological differences and sample size are other factors warranting scrutiny. Also, the interpretation of results is limited by the near exclusive reliance on self-reported data. This is due to the difficulty in recording polysomnographic data from a general population especially when a whole country is involved. However, future epidemiological research should try to increase the reliability of data collected. One possibility is to conduct a study with polysomnographic recordings of a cohort randomly drawn from the general population.
At this point in time, the picture of sleep disorders in the general population remains hazy, but a
sharper resolution is in the offing as the research steadily grows and improves.
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