A number of studies have shown that persons reporting more persistent insomnia attribute poor waking function to poor sleep (2-6). In the Addison et al. study (4), daytime activities of 27% of a national representative sample were negatively affected by poor sleep at least two days per week. For those dissatisfied with their sleep, this percentage increased to 70%. A later Gallup study (2) found that insomniacs report poor performance at work, memory difficulties, concentration problems, and twice as many fatigue-related automobile accidents as compared to good sleepers. The latter finding regarding automobile accidents was not replicated in the 1995 Gallup study (3). Nevertheless, there is some additional evidence that accident rates in general (7), and drowsy driving are increased in individuals with poor sleep (7, 8). A longitudinal study of Navy personnel found that poor sleepers, in comparison to good sleepers, earned fewer promotions, remained at lower paygrades and received fewer recommendations for reenlistment (9). Academic performance may also be worse in insomniacs. Blum et al. (10) reported 21% of poor sleeping preadolescents had failed at school compared to 11% of good sleepers. Perceived sleep quality also has been reported to be positively associated with academic performance in medical school (11).

A small number of laboratory studies of alertness and performance of chronic insomniacs have found objective deficits in memory, daytime vigilance and gait and balance (12-15, 23); however, a number of other investigations have found essentially no differences between insomniacs and noninsomniacs (18, 25-28). Insomniacs are usually recruited for participation in these laboratory studies and there is evidence that recruited patients may not be representative of insomniacs seeking medical attention (16). Moreover, the studies generally include insomniacs without medical or psychiatric conditions, many of whom would be diagnosed with psychophysiological or primary insomnia. There is evidence that this subtype of insomnia may be "hyperaroused" and thus may not readily show the routine deficits that accompany significant sleep loss (15, 17). Finally, there are studies of chronic insomnia associated with arthritis (19) and periodic limb movement disorder (20) that show moderate levels of daytime sleepiness, as well as an increase in daytime alertness when sleep is improved with a short-acting hypnotic during one week of treatment. In other studies such increases in objectively measured alertness often are accompanied by improved performance on laboratory performance tests.

None of the studies of chronic insomnia allows a conclusion of causality; poor sleep and the waking impairment may both be a result of a psychological or physiological dysfunction. However, the possibility that poor sleep contributes to these reports of impaired waking function cannot be dismissed at this time.

Quality of Life

Quality of life (QoL) is difficult to define, although a widespread and intuitively understood concept. Indeed some authors (29) argue that only patients can characterize those factors which contribute to their QoL. The World Health Organization has defined QoL as individuals' perception of their position in life in the context of the culture and value systems in which they live and in relation to their goals, expectations, standards and concerns (32). Based on this definition, it seems logical that QoL for many individuals with insomnia would be lower than for good sleepers. This judgment is based upon a voluminous literature (35) on insomnia which demonstrates increases in psychological distress, negative mood, psychiatric illness, medical illness, perceived cognitive deficits, health care utilization, institutionalization, and a variety of other negative correlates, relative to non-insomniacs. The degree to which poor sleep independently accounts for these negative associations has yet to be clarified, and will determine, in part, the direct impact of insomnia on QoL.

Generic measures of QoL cited in the literature frequently include items which assess sleep, an indirect acknowledgment that poor sleep negatively impacts QoL. For example, the Sickness Impact Profile (33) includes seven items dealing with sleep and rest and the Medical Outcomes Study (34) included 12 items about sleep. Many disease-specific QoL instruments have been developed, but a search of the English language literature revealed no insomnia-specific QoL instrument.

Very few studies have attempted to measure QoL with relation to insomnia. Goldenberg and colleagues (30) compared the effect of a 14-day administration of either zopiclone 7.5 mg or placebo to 458 insomniacs in five countries. The authors report greater improvement in the active drug group on measures of professional and social life indicators, but not for psychological well-being or a global evaluation item. No non-insomniac control subjects were included. Leger et al (31) compared 167 patients taking zopiclone for 12-months to a control group of 381 normal sleepers. No differences were found between groups for measures of leisure, domestic, professional, relational, and safety aspects of life. No information was presented with regard to the dose or frequency of use (continuous versus intermittent) of zopiclone during the 12-month period.

Almost all studies have either not considered diagnostic subtype of insomnia, or have combined insomnia of various types when measuring consequences. It is possible, in fact likely, that the consequences of insomnia differ among insomnia subtype. For example, there is evidence that primary or psychophysiological insomniacs may be "hyperaroused" and thus may not readily show the routine deficits that accompany sleep loss (15). On the other hand, there are studies of chronic insomnia associated with arthritis (19) and periodic limb movement disorder (20) that show evidence of daytime sleepiness and an increase in daytime alertness when sleep is improved with a short-acting hypnotic.

The outcome measures of waking function have often been brief psychomotor tasks, known or thought to be sensitive to sleep loss . However, the majority of insomniacs recruited to participate in these studies are those who do not appear to be physiologically sleepy during the day (12, 15, 17, 18). More research is needed with outcome measures that assess higher order cognitive, psychological and emotional functions. Cognitive abilities include abstract thinking, concept formation, reasoning, planning, and memory. Cognitive and psychomotor categories are not absolutely dichotomous, as many tasks involve varying degrees of lower and higher order abilities. Nevertheless, it is reasonable to expect differential sensitivity.

Most studies have included subjects recruited specifically for the research investigation, as opposed to studying patients seeking medical attention for their sleep problem; this latter group may represent individuals with more significant waking impairment (16). Somewhat related to this concern, most studies have not documented insomnia severity, in terms of objective sleep disturbance, often relying only upon global self-report. Variability in the degree of physiologic sleep disruption in these samples would be very high, precluding consistent effects upon waking function.

Few studies of insomnia and waking behavior have employed a design which would allow comparison of treated versus untreated insomnia. This is important in that the comparison of insomniacs versus normals may not be as relevant as the comparison of treated versus untreated insomnia. Balter and Uhlenhuth (7) demonstrated with a retrospective survey study that pharmacological treatment did appear to improve waking function in insomniacs. As mentioned above, two studies of chronic insomnia associated with arthritis (19) and periodic limb movement disorder (20) demonstrated an increase in daytime alertness when sleep was improved with pharmacological treatment.