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SF-36: Evaluation of Quality of Life in Severe and Mild Insomniacs Compared With Good Sleepers

From Centre du Sommeil (D.L., K.S., P.P., M.P.), Hôtel-Dieu de Paris, Paris, France; and the Sleep Disorders Clinic (C.G.), Stanford University, Stanford, California.

Address reprint requests to: Damien Léger, MD, Centre du Sommeil, Hôtel-Dieu de Paris, 1 Place du Parvis Notre-Dame, 75151 Paris Cedex 04, France.

	ABSTRACT

TOP ABSTRACT INTRODUCTION METHODS RESULTS DISCUSSION ACKNOWLEDGMENTS REFERENCES

 
OBJECTIVE: Despite many studies, the impact of chronic insomnia on daytime functioning is not well understood. The aim of our study was to detect this impact by evaluating quality of life (QoL) using a validated instrument, the 36-item Short Form Health Survey of the Medical Outcomes Study (SF-36), in three matched groups of severe insomniacs, mild insomniacs, and good sleepers selected from the general population.

METHODS: Three matched groups of 240 severe insomniacs, 422 mild insomniacs, and 391 good sleepers were recruited from the general French population after eliminating those with DSM-IV criteria for anxiety or depression. All subjects were asked to complete the SF-36. Scores for each QoL dimension were calculated and compared statistically among the three groups.

RESULTS: Severe insomniacs had lower QoL scores in eight dimensions of the SF-36 than mild insomniacs and good sleepers. Mild insomniacs had lower scores in the same eight dimensions when compared with good sleepers. No dimension was significantly more altered than the other.

CONCLUSIONS: The mental health status and role of emotional QoL dimensions were worse in severe and mild insomniacs than in good sleepers. This result held even though we screened for psychiatric diseases, which shows a clear interrelation between insomnia and emotional state. General health status was also worse in severe and mild insomniacs than in good sleepers. However, we could conclude only that insomnia was related to a worse health status and not whether it was a cause or consequence of this worse health status. Finally, the degradation of QoL scores was correlated with the severity of insomnia.

Key Words: insomnia • quality of life • sleep.

Abbreviations: ANOVA = analysis of variance; DSM-IV = Diagnostic and Statistical Manual of Mental Disorders, fourth edition; ICSD = International Classification of Sleep Disorders; MSLT = multiple sleep latency test; QoL = quality of life; SF-36 = 36-item Short Form Health Survey of the Medical Outcomes Study.

	INTRODUCTION

TOP ABSTRACT INTRODUCTION METHODS RESULTS DISCUSSION ACKNOWLEDGMENTS REFERENCES

 
Insomnia is a common complaint in the general population (1–3). Patients suffering from insomnia usually complain of poor sleep and impaired daily functioning. Indeed, the definition of insomnia (4, 5) includes its daytime consequences, especially daytime sleepiness. The ICSD (5) notes that "insomnia is always associated with a complaint of decreased functioning during wakefulness." The DSM-IV (4) describes insomnia as a condition "serious enough to induce severe fatigue or signs attributable to insomnia and marked by symptoms such as irritability or disability in daytime functioning" or that "is frequently accompanied by nonspecific symptoms such as mood disorders, memory troubles, or lack of concentration."

However, only a few of the epidemiological studies conducted on insomnia have focused specifically on the evaluation of these daytime impairments, and it is still difficult to establish a direct correlation between chronic insomnia and daytime sleepiness (1, 6, 7). Many studies have shown the impact of transient insomnia on daytime functioning. A temporary loss of sleep may affect dramatically the daytime functioning of these subjects (8). When experiencing unusually poor sleep, people report a decrease in performance during the day that is linked to increased sleepiness due to the sleep deprivation experienced the night before (9). In chronic insomniacs, however, who continuously experience poor sleep, studies are less consensual. Some studies have tried and failed to demonstrate the impact of chronic insomnia on daytime functioning. For example, Stepanski et al. (10) showed that, compared with control subjects during MSLTs, chronic insomniacs do not have impaired alertness. One may argue that insomniacs who already experience difficulties in falling asleep at night might also have difficulties in resting during daytime. It may also be proposed that objective tests like MSLTs are too rough to assess the daily impact of insomnia and that, consequently, QoL instruments may reflect more accurately the daily impact of insomnia. However, up to now, little has been known about the QoL of insomniacs.

QoL is a complex and multidimensional term that has been defined as "a concept encompassing a broad range of physical and psychological characteristics and limitations which describe an individual’s ability to function and to derive satisfaction from doing so" (10). It includes the following domains: the physical, encompassing the ability to conduct activities of daily living; the psychological or emotional; and the social, encompassing interactions with family, friends, and community (11). Insomnia may affect all three of these domains.

We therefore decided to focus our study on the QoL of insomniacs. Few studies have been designed specifically to evaluate the impact of insomnia on QoL. Two of these studies were conducted in insomniacs treated with zopiclone (12–14), a third study compared a group of insomniacs and a group of good sleepers selected from a group of managed-care enrollees (15), and another compared a group of insomniacs and a group of good sleepers selected through telephone interviews (16). In our study, we also wanted to explore whether the degree of QoL impairment was linked to the severity of insomnia.

To achieve this, we used the standardized SF-36 to evaluate QoL in three groups selected from the French general population: good sleepers, mild insomniacs, and severe insomniacs.

	METHODS

TOP ABSTRACT INTRODUCTION METHODS RESULTS DISCUSSION ACKNOWLEDGMENTS REFERENCES

 
Subjects and Controls
SOFRES, a French polling institute, was used to select subjects for the study. This institute regularly conducts surveys of a group of 11,372 individuals who are representative of the general French population. Initially, each individual received the first questionnaire (Q1), which assessed insomnia based on DSM-IV criteria (17). This questionnaire had been previously used in epidemiological surveys to select groups of mild and severe insomniacs (18, 19). Severe insomniacs were categorized as having at least two sleep complaints (including difficulties initiating and/or maintaining sleep and experiencing nonrefreshing sleep and/or early awakenings) at least three times a week for at least 1 month along with a complaint of impaired daytime functioning. Of the 8625 individuals who responded to the poll (76%), 690 were classified as severe insomniacs (8.1%). A matched group of 700 persons with mild insomnia and a group of 600 individuals who had no sleep problems at all were also selected. Mild insomniacs were defined as people who had occasional sleep difficulties that were statistically significant when they were compared with good sleepers but who did not meet the criteria to be categorized as severe insomniacs. The three groups were statistically similar for the following variables: age (five age groups were formed: 18–24, 25–34, 35–49, 50–64, and 65 years), sex, occupation (consisting of eight subcategories), location, marital status (married, living together, single, divorced, or widowed), and socioeconomic status (consisting of six subgroups).

Questionnaire Q2
To assess QoL in subjects without depression or anxiety disorders, we subsequently sent Q1 respondents a second questionnaire (Q2). The purpose of Q2 was two-fold: 10 items were aimed at detecting psychiatric disorders (based on DSM-IV definitions of anxiety or depression), and the other questions concerned SF-36 items. General information such as sex, age, occupation, marital and matrimonial status, location, and habitat were also recorded.

The first part of Q2 included 10 items based on the DSM-IV minimum criteria for anxiety and depression; these questions were used to eliminate persons with such conditions. An individual was classified as "presenting a depression profile," and thus eliminated from the study, when he or she had two of the following three symptoms for >15 days: 1) being sad or depressed most of the time during the day, almost every day; 2) having lost interest in activities that are normally pleasing; and 3) being tired all the time. An individual was classified as "presenting an anxiety profile" when, during the last 6 months, he or she had had one of the two main anxiety symptoms (being anxious or worried most of the time or being apprehensive toward daily problems), continued to present the symptom(s), and had had the symptom(s) for >6 months.

The second part of Q2 included the 36 items from the SF-36. The SF-36 contains nine dimensions related to health and functional ability and is currently used to measure QoL. The nine dimensions are physical functioning, social functioning, role limitations due to physical problems, role limitations due to emotional problems, mental health, vitality, bodily pain, general health, and health change in the past year. Each dimension is evaluated through a series of questions (hence, the 36 items) that add up to a score in each dimension, the best score being one that is close to 100. Lower scores indicate a lower QoL. The SF-36 was previously translated into French and has been validated (20).

The questionnaire was mailed with a postage-paid return envelope. Participants received neither a fee nor a reward for taking part in the study.

Of 690 severe insomniac respondents to the Q2, 538 (78%) were nonpsychiatric severe insomniacs; 1060 of 1300 (81%) mild insomniacs and good sleepers (614 and 446 individuals, respectively) had no psychiatric disorders. Persons who, according to DSM-IV minimum criteria for anxiety and depression, presented with psychiatric disorders had been eliminated from each group. After this screening, subjects were matched for socioeconomic status, and the three groups were thus reduced to 240 severe insomniacs (SI group), 422 mild insomniacs (MI group), and 391 good sleepers (GS group) (see Figure 1). These three groups were once more compared for socioeconomic status and were not found to be statistically different in terms of age, occupation, marital and matrimonial status, location, and habitat.

View larger version (50K): [in this window] [in a new window]   Fig. 1. Makeup of the three groups after completion of Q2.

Further statistical analyses were performed using ANOVA with post hoc comparison with Bonferroni and Scheffe tests, Student’s t test, and ² with a level of significance of 95%.

	RESULTS

TOP ABSTRACT INTRODUCTION METHODS RESULTS DISCUSSION ACKNOWLEDGMENTS REFERENCES

 
Table 1 and Figure 2 show the results in the three groups (significance determined by ANOVA with post hoc comparison). Severe insomniacs had worse mean scores in eight dimensions when compared with mild insomniacs and good sleepers. There was no significant difference between the SI and MI groups or the SI and GS groups in the dimension "reported health transition." Mild insomniacs also had worse mean scores in eight dimensions compared with good sleepers. Here again, there was no significant difference in the dimension "reported health transition" between the MI and GS groups.

View larger version (18K): [in this window] [in a new window]   Fig. 2. Distribution of the different subscales of the SF-36 for each of the three study groups. ; = good sleepers (N = 391); ; = mild insomniacs (N = 422); ; = severe insomniacs (N = 240).

Physical Functioning
For all items of physical functioning (divided into normal everyday efforts, unusually hard efforts, effort going up stairs, and walking and lifting efforts), the SI group did significantly worse than the GS and MI groups. Although there was a difference in the total dimension score between the MI and GS groups, there was almost no difference between these groups when this dimension was taken item by item.

Role–Physical Functioning
Subjects in the SI and MI groups felt significantly more impaired in their normal activities because of their physical limitations than subjects in the GS group. SI subjects were also significantly more impaired than MI subjects.

Bodily Pain
SI subjects felt more bodily pain than MI and GS subjects, and there was no difference between the MI and GS groups (see Table 2). However, there was no significant impairment in the accomplishment of their daily tasks due to bodily pain.

Role–Emotional Dimension
SI and MI subjects were significantly more impaired by emotional disturbances than GS subjects during the day (see Table 3).

Reported Health Transition
When asked how they compared their general health status at the time of the study with 1 year before, 79% of GS subjects, 73% of MI subjects, and 63% of SI subjects answered that, on average, it was the same (no significant difference was found when the GS and MI, MI and SI, or SI and GS groups were compared).

	DISCUSSION

TOP ABSTRACT INTRODUCTION METHODS RESULTS DISCUSSION ACKNOWLEDGMENTS REFERENCES

 
Methods
From a representative sample of France’s general population, we selected groups of individuals who were comparable in all demographic criteria and differed only in the occurrence and severity of sleep disorders. We used a questionnaire based on DSM-IV criteria to define severe insomniacs; therefore, we had no polysomnographic recording to assess whether these subjects were really suffering from insomnia. Moreover, we did not investigate the causes of insomnia in this study, and several subjects may have had their sleep disturbed by somatic diseases. However, we had already used and validated this questionnaire in extensive studies (18, 19); it was deemed appropriate because the aim of the study was not to differentiate primary or secondary insomnia but to evaluate the consequences of poor sleep on QoL.

We also wanted to avoid certain factors of confusion in the determination of the daytime consequences of insomnia. Depression or anxiety disorders may have considerable effects on the daytime functioning of subjects and thus entail significant QoL impairments, especially when evaluating mental health and the role of emotional dimensions. This is why we eliminated patients presenting depression or anxiety disorders from our group. However, it has already been shown that insomnia and psychiatric disorders such as anxiety and depression are intertwined. Mellinger et al. (21) emphasized that "insomnia could be the cause or the consequence of psychological troubles appearing coincidentally." In addition, Ford and Kamerow (22) have already demonstrated in a prospective study that insomniacs without treatment were 4.5 times more likely to develop depression and alcoholism than insomniacs who were treated. In our study, there were also significantly more people with depression and anxiety disorders in the prescreening SI group than in the prescreening GS group. Thus, by eliminating patients with anxiety and depression disorders from our study (some of whom, hence, were probably suffering from depression and anxiety resulting from insomnia), we knew we would be underestimating the impact of insomnia on QoL.

To eliminate patients with anxiety and depression symptoms, we also used a questionnaire, although we were aware that direct interviews with patients would have been a more accurate way to determine their psychiatric status. However, considering the significant number of people studied and their geographic dispersion over the whole French territory, we deemed that these interviews could not be practically conducted because of logistics.

Results
In this study, we showed that chronic insomniacs complain of a worse QoL than do good sleepers and that the more severe the insomnia, the worse the QoL. Furthermore, we established that insomnia seems to affect all dimensions of QoL. There is no particular domain in which insomnia seems to have greater consequences than in others. The only dimension that was not significantly different was the reported health transition dimension, with all groups estimating that their general health status at the time of the study was, on average, similar to that of the previous year. This can suggest that insomnia impairs QoL progressively on a long-term basis (over several years) and not acutely in the short term.

These results are new, because surprisingly very few studies have been devoted to the QoL of insomniacs. The World Health Organization consensus report on sleep and health heavily recommends more studies on the QoL of insomniacs (23). However, to our knowledge, only four studies have been conducted on this subject. Goldenberg et al. (12), using their own QoL instrument, showed that 458 patients from five countries treated with zopiclone for 14 days had significantly greater improvement than placebo recipients in sleep evaluation questions and scores for the activity and social and professional QoL aspects. After completion of this study (8 weeks later), scores for activity and QoL remained significantly higher in patients who had received zopiclone. Also using their own QoL instrument, Léger et al. (13, 14) investigated the QoL of 167 patients who had been using zopiclone for the previous 12 months and compared results with those obtained from a control group of 381 patients with no sleep problems. No significant differences were observed between the two groups in almost all five aspects of the QoL questionnaire explored (leisure, domestic, relational and sentimental, professional, and safety aspects). Hatoum et al. (15) used the SF-36 to evaluate QoL of insomniacs compared with good sleepers selected from a large group of managed-care enrollees and found worse QoL scores in insomniacs in all dimensions of the SF-36. A more recent study (16) also used the SF-36 to explore QoL among a group of 261 insomniacs and a group of good sleepers. It showed that insomnia is associated with significant QoL impairments and suggested that no particular dimension of QoL seemed more affected by insomnia than any other. We found similar results, because in our study results on eight of the nine dimensions of the SF-36 were significantly worse in insomniacs than in good sleepers. However, hitherto, no study had compared these three groups: DSM-IV–defined insomniacs (our SI group), a matched group of mild insomniacs, and a matched group of good sleepers, with all groups selected from the general population. As Figure 2 shows, we found a gradation between the three groups, confirming that the worse the insomnia, the worse the QoL. Also, we confirmed in this study that the SF-36 seems to be a good instrument to assess QoL in insomniacs and, consequently, the daytime consequences of insomnia, because it seems to be sensitive to the severity of insomnia.

To correctly interpret the results of this study regarding the impact of insomnia on QoL, it is also important to consider the relationship between insomnia and general health status. In this study, we did not investigate the causes of insomnia. It is thus possible that some of the severe insomniacs suffered, concomitantly, from other chronic illnesses that might by themselves have triggered worse QoL scores. The general health status dimension of the SF-36 shows that severe insomniacs complain of a worse health status than good sleepers and mild insomniacs. Several studies have shown that clinical disorders are linked to poor sleep (24). Conversely, insomnia has also been suspected of promoting clinical and psychiatric pathologies (22, 25). One interesting aspect of that debate is illustrated in the SF-36 QoL scale through the relationship between insomnia and bodily pain. Bodily pain caused by various illnesses (cardiac, respiratory, joint diseases, and the like) may of course result in poor sleep and concomitant poor QoL; however, it is also possible that sleep deprivation and poor sleep may increase the sensitivity of insomniacs to pain. Thus, on the basis of the results of this study, we can only say that a strong link exists between insomnia and bodily pain. Similarly, we cannot tell whether the poor QoL observed in severe insomniacs is due to poor sleep or to poor health resulting further in poor sleep. However, we may say that a strong association exists between insomnia and QoL and that the more severe the insomnia, the worse the QoL. The study by Hatoum et al. (15) found that after controlling for demographic variables and comorbid conditions, the negative association of insomnia remained significant in all the participants’ SF-36 QoL scores. It seemed, then, that in addition to the deteriorated QoL due to other diseases, insomnia appeared as an independent factor that could explain the worse QoL of insomniacs when compared with good sleepers. This emphasizes the importance to physicians of carefully investigating the complaint of insomnia.

Another important point highlighted in this study is the emotional impact of insomnia (see Table 3). Patients with insomnia frequently complain of anxiety and emotional problems. Anxiety has been shown to be associated with insomnia, and patients with anxiety also have a high rate of insomnia (26, 27). Despite the fact that we had eliminated subjects with likely DSM-IV–defined anxiety and depression, we found a clear emotional aspect of insomnia that can be assessed by the several items devoted to that topic. To better understand this interrelation between insomnia and emotional aspects, more studies have to be conducted.

In conclusion, we found, predictably, that a more severe form of insomnia was associated with lower levels of QoL. General health status also worsened with the severity of insomnia. As a result, we could not conclude whether insomnia was the direct cause of the lower QoL scores or whether they resulted from a degraded health status that in itself entailed a more severe form of insomnia. Nevertheless, our study showed that the SF-36 was sensitive to the severity of insomnia and seems then to be a reliable instrument for assessing the impact of insomnia on QoL. The use of the SF-36 as a tool to assess the different management strategies of insomnia (28) may be helpful.

	ACKNOWLEDGMENTS

TOP ABSTRACT INTRODUCTION METHODS RESULTS DISCUSSION ACKNOWLEDGMENTS REFERENCES

 
This work was supported by a grant from Theraplix, Rhône-Poulenc-Rorer. We thank J. P. Dreyfus and F. Loos at SOFRES.

Received for publication December 31, 1999.

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TOP ABSTRACT INTRODUCTION METHODS RESULTS DISCUSSION ACKNOWLEDGMENTS REFERENCES

 

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This Article Abstract Figures Only Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Léger, D. Articles by Guilleminault, C. Search for Related Content PubMed PubMed Citation Articles by Léger, D. Articles by Guilleminault, C. Related Collections Quality of Life Sleep and Biological Rhythms