Daytime sleepiness: a risk factor in community lire Martikainen K, Urponen H, Partinen M, Hasan J, Vuori I. Daytime sleepiness: a risk factor in community life. Acta Neurol Scand 1992: 86: 337-341. 0 Munksgaard 1992
I
The prevalence of daytime sleepiness and background factors associated with it were investigated in a study carried out at the UKK Institute. The inquiry took the form of a questionnaire mailed to 1600 people of middle age. Daytime sleepiness was found to be associated with disturbed night sleep. Women were more tired than men, but men slept more frequently during the day. Those suffering from tiredness complained of poor health more than other respondents. Traffic accidents and other mishaps attributable to tiredness had occurred in 1.3% of cases, and almost 5 % of male respondents had dozed off while driving at least five times in their lives. The findings indicate a need for increased attention to disturbance of sleep and daytime sleepiness in routine health screening.
The Finnish word “vasymys” may express not only sleepiness but also exhaustion. According to the latest international classification of sleep, sleepiness means difficulty in maintaining an alert waking state, this being divided into three grades of severity. Mild sleepiness manifests itself in states of rest and in tasks requiring for little attentiveness; moderate sleepiness may hamper even slight physical activity and tasks calling for a moderate degree of alertness, as for example driving; in its serious form, sleepiness is manifested daily even in the course of physical activities such as eating and walking, and the detriment to social intercourse and work life is considerable. Fatigue and tiredness, on the other hand, are mentioned as daytime symptoms associated with insomnia (1). In material from the sleep clinics the sleep apnoea syndrome is the most common disorder associated with excessive daytime sleepiness; other illnesses inducing tiredness are narcolepsy, idiopathic hypersomnia and nocturnal myoclonus. Not all daytime sleepiness, however, is attributable to illness. In addition to inadequate night sleep (2), a variety of factors such as shift-work and medication may be the cause. A number of those complaining of tiredness are suffering from more general exhaustion, underlying which is in many cases a state of depression. The purpose of the present study was to ascertain the prevalence of subjectively experienced daytime sleepiness, together with factors associated with it, in an unselected middle-aged urban population. With
K. Martikainen’, J. Hasan’, H. Urponen3, I. Vuori3, M. Partinen4
’
Hatanpaanpuisto Hospital, Tampere University Hospital, UKK Institute, Tampere, Department of Neurology, Kivela Hospital, Helsinki, Finland.
Hatanpaanpuistokuja 8, 33 100 Tampere, Finland Accepted for publication January 15, 1992
an eye to obtaining as comprehensive a picture as possible of the situation, particular attention was paid to the diversity of questions on tiredness and the precision of alternative answers (Table 1).
Table 1. Questions on tiredness and alternative answers Have you felt tired during the daytime within the last three months? Not once Less than once a week One or two days a week Three to five days a week Daily or almost daily How often have you taken a nap during the day within the last three months? Not once Less than once a week One or two days a week Three to five days a week Daily or almost daily Have you felt a compulsive desire to sleep in the course of your ordinaty tasks within the last three months? Not once Less than once a week One or two days a week Three to five days a week Daily or almost daily Several times a day Do you feel that you are generally more tired than your friends and colleagues? Not more tired but clearly more sprightly than they Not more tired but soemwhat more sprightly I find no difference Yes, I am somewhat more tired than they Yes, clearly more tired
331
Martikainen et al. Material and methods
The study was carried out in 1985 at the UKK Institute in Tampere, and took the form of a mailed questionnaire. Subjects were picked by a stratified random sample (N = 1600) of the adult population of Tampere, so structured as to comprise 200 men and 200 women from each of the age groups 36-, 41-, 46- and 50-years. The questionnaire was completed by 1190 people, a response constituting 75.2% of the total sample, 81% (N=641) of women and 69% (N=549) of men. The lowest response percentage (53%) was in the group 41-year-old men ( 3 ) . In addition to completing the questionnaire the subjects kept a record of their sleep for one week. Questions on tiredness and quality of sleep focussed on the three months preceding the time of inquiry. Further questions concerned snoring, general health, medication, stimulants, education, occupation, working hours, living habits - here in particular exercise - and height and weight. The designation "tired" was applied to respondents who considered themselves to be clearly more tired than their acquaintances and colleagues, who experienced daily a compulsive desire to sleep in the course of their normal undertakings, or who felt tired every day. The results of the inquiry are crosstabulated by sex and age. Statistical significance was assessed by the X-square test.
Results Prevalence of tiredness
On the above criteria, a total of 117 (9.8%) people were classified as tired; of these, 38 (32.5%) were men and 89 (67.5%) women. Four of the total, two men and two women, had complained of all the forms of tiredness mentioned. The condition was clearly more common among women; of the women responding to the inquiry 12% were classed as tired, as against 6.9% of the men. On the other hand, men more frequently slept during the day. The material included two narcoleptic patients, both of them women.
Table 2. Tiredness (%I by age and sex ~
~
~
Men (N=549)
Age groups Daytime sleepiness Never More seldom than once a week 1-2 daysa week 3-5daysaweek Daily
Women (N=641I
36 %
41 %
46 %
50 Total 36 % % %
10
12
11
12
11
39 3 1 37 39 31 35 39 30 12 10 9 11 8 6 4 8
38 34 10 7
Compulsion to sleep Never 13 73 6 1 15 72 More seldom than once a week 20 21 24 17 21 1-2 days a week 5 3 6 6 5 3-5 days a week 1 2 2 1 1 Daily or many times a day 1 1 1 1 1 Generally more tired Clearly more alert More alert No difference More tired Clearly more tired
6 4 8 6 8 7 1 3 5 79 82 12 79 6 5 1 9 1 2 - 1
41 46
%
%
5
4
50 Total % %
7
5
35 3 1 39 29 42 40 35 41 5 9 8 11 13 9 1 4 1 2
35 40 8 12
6 1 71
13 66
69
22 19 20 18 6 5 2 1 2 2 3 1 2
20 6 2
5
3
2
4
6
3 8 2 10 9 1 1 78 71 12 16 1 1 6 1 1 3 1 - - 3
8
2
3
8 8 71 1 1
5 10 12 1 1
Overweight
Fig. 1 shows the correlation between tiredness and overweight. Those complaining of tiredness were on the average heavier than others: at least 20% overweight (BMI > 30 kg/m2) was recorded for 2 1% of sufferers, as against only 9.3% of all respondents. Quality of sleep
Twenty-seven questions were devised to elicit data on quality of sleep and factors disturbing it ( 3 ) . On
% iM,
,
60
Age
Reports of tiredness were particularly evenly distributed over the various age groups. The only statistically significant association of age was with daytime sleeping among the men (p = 0.004). Men over 50 were most prone to take a nap during the day, 21 % of them on at least three days a week and 10% daily. The occurrence of the various forms of tiredness is set out in Table 2.
338
40
20
0
...
Men
'
TIRED
Men
Women
Normal + 10% overweight
Approx. 20 X overweight
Fig. 1 . Tiredness and overweight.
ALL
Women Approx. 30 % werweiQhl
Daytime sleepiness Table 3. Subjective assessment of health in tired group and whole material (%) Tired
Table 4. Characteristics of subjects involved in traffic accidents attributable to tiredness
N=15
Total
Men %
Women %
Total %
Men %
Women %
Total %
Good Fairly good Average Rather poor or poor
16 40 32
15 24 47
15 29 42
34 40 23
30 40 26
13
14
14
3
4
3
N
38
89
117
549
641
1190
32 40 25
average, those complaining of tiredness reported all the disturbing factors involved more consistently than did the group as a whole. There were, however, no significant differences in respect of the use of sedatives. Tired subjects were more apt than respondents in general to consider their sleep poor; this applied to 5 % of those reporting tiredness, in contrast to 0.7% of the total. A particularly common disturbance reported by the former was waking during the night, mentioned by 42% of tired subjects as against 18% in the whole material. Subjective state of health
The respondents’ own assessment of their health was elicited with the question: How good do you consider your general state of health to be at the moment? Those complaining of tiredness gave more negative assessments than the average, and the most negative assessments came from those who felt they were more tired than others. Of these, 14% considered their health rather poor and 4% poor, while only 9% felt they were in good health. Of those reporting proneness to fall asleep, 12% considered their health rather poor and 4.9% poor. The health of sufferers compared to that of other respondents is shown in Table 3. Work
Among those reporting tiredness, 2 1 (18 %) were on 2- or 3-shift work or night work, the corresponding figure for the whole material being 13%; 15% of sufferers, again, described their work as irregular, as against 10% of all respondents. Those complaining of a compulsive tendency to doze were more likely than other tired subjects to be totally withdrawn from work life, and none was engaged in night work. Only eight subjects had been reprimanded at work in consequence of tiredness, three of these belonging to this group.
Alcohol consumption over 10 occasions a week Unemployed of absent from work Poor sleep Snores every night Daytime sleepiness 3-5 days in the week Overweight by over 20% Shift-work Tiring medication
n
% 40 40 40 27 27 27 20 20
Driving
Among those in the whole material who drove a car or other vehicle, 15% (173 people) had dozed off at the wheel at least once in their lives. Among the men 4.6% reported at least five such occasions. Traffic accidents or other mishaps attributable to tiredness had occurred to 15 persons, that is, 1.3% (1.8% of the men, 0.3% of the women). Only one of these belonged to the last-described group of tired subjects, but four of them reported tiredness on at least three days in the week, and in three cases the tiring effect of medication was possibly a contributing factor. Other background factors to emerge were nightly snoring, heavy consumption of alcohol, unemployment, shift-work, disturbance to sleep and overweight (Table 4). The proportion of absentees from work was clearly greater than expected in the group involved in accidents as compared to the rest (40% vs 5.8%). Probable causes of tiredness
Judging from the replies to the questionnaire and the sleep log material, the most common cause of tiredness was disturbance of night sleep ( 5 6 % ) . Here, the most frequent disturbing factor was snoring, which in some cases (7/31) also involved irregular breathing with respiratory pauses during sleep. Nightly snoring was reported by 32% of those suffering from tiredness. Other common sources of disturbance to sleep were anxiety and tension, especially in the case of older women various pains, and among young women, their children and pregnancy. Two subjects reported that asthma symptoms broke their sleep, and one subject mentioned the frequent need to relieve himself. Tiredness attributable to psychosocial factors without actual disturbance to sleep troubled 18% of respondents. Among tired subjects, 12% were on shift-work and in 9% the probable reason for tiredness was excessively short night sleep. Diagnosed narcolepsy was the source in 1.7 % of tired subjects (N = 2, 0.17% of all respondents).
Martikainen et al. A number of cases clearly involved several concomitant factors inducing tiredness; subjects suffering from tension and insomnia resorted to sedatives for relief. Shift-work frequently involved disturbed and occasionally curtailed night sleep. The role of alcohol as a source of disturbance to sleep was difficult to ascertain by reason of the inadequacy of answers on alcohol consumption. Discussion
Tiredness may take the form of sleepiness outright, involving a tendency to doze off. On the other hand it may also mean a state of exhaustion. Either case involves detriment to work life and social intercourse. Sleepiness, however, is considered the more dangerous form by reason of the risk of accident, especially in traffic and other situations calling for particular alertness. Figures for the prevalence of daytime sleepiness have varied from 0.5% to 14% (4-9). In a National Pensions Board study (9), 9.3% of the adult population (1099 people aged 29-79 years) reported feeling more tired than their acquaintances. In a questionnaire inquiry conducted by the National Board of Health (2016 people aged 15-64years), 10% of men and 14% of women assessed themselves as more tired than their friends and colleagues, and 3% reported suffering daily or almost daily from a compulsive desire to sleep (5). The type and severity of the daytime sleepiness reported in questionnaire studies are often difficult to assess. Tiredness has not been objectively confirmed in these cases, nor has any closer study been made of background factors possibly contributing to disturbance of night sleep. Daytime sleepiness is a common problem involving detriment to well-being and work efficiency. In most cases it is associated with lack of sleep or deficient quality of sleep. In the present study, tiredness turned out to be a particularly common symptom among people of work age. The figures for prevalence corresponded to those obtained in other Finnish studies. The more specific reasons for tiredness cannot be defined on the basis of the present findings. If, however, the probable causes are judged from answers received, the fact emerges that among subjects complaining of tiredness the majority reported disturbed or curtailed night sleep. Although sleep apnoea is not the most common significant cause of tiredness elicited in a study such as this, the most prominent single group among disturbing factors was nightly snoring. The apnoea syndrome was suspected in seven of the sufferers (6%) on the criterion of loud habitual snoring associated with apnoeas and tiredness. Exhaustion was recorded in 21 cases (18%)
340
among the tired subjects. The predominance of women among sufferers may be due partly to their different life situation but also to their different ways of experiencing and expressing things. In the case of older women an additional factor disturbing night sleep is the menopause. The present observations would indicate that even the forms of tiredness leading to or rendering liable to traffic accidents constitute a significant phenomenon. Over half of those mentioning involvement in accidents as a result of tiredness reported feeling tired many days in the week or snoring every night. The figures for accidents were of the same magnitude as those obtained by Partinen in 1982 (10). In the issuing of driving licenses closer attention should be paid to these considerations than hitherto. Of the clientele of the sleep clinics, the greater proportion of whom suffer specifically from daytime sleepiness, almost half have been involved in motor accidents, and over half have had accidents at work (11, 12). The study and care of daytime sleepiness has in general received scant attention, in spite of the fact that the evergrowing demand for efficiency in work life and the increased volume of motorized traffic emphasize the importance of vigilance. Engagement on work tasks calling for an alert state of mind applies to an increasing proportion of the population, and ever more seldom does merely keeping awake suffice in the discharge of work tasks. If the reasons for symptoms of tiredness cannot be ascertained in basic health service facilities, help can be sought from physicians specializing in disturbances of sleep. Acknowledgement This study was supported by the Yrjb Jahnsson Foundation.
References 1. The International Classification of Sleep Disorders. Diagnostic and coding manual. Am Sleep Disorders Assoc, Rochester, 1990. 2. ROEHRS T, ZORRICK F, SICKLESTEEL J etal. Excessive daytime sleepiness associated with insufficient sleep. Sleep 1983: 6: 319-325. 3. URPONEN H, VUORI I, HASANJ, PARTINEN M. Selfevaluations of factors promoting and disturbing sleep. J SOCMed 1987: 24: 15-27. 4. FRANCESCHI M, ZAMPRONI P, CRIPPAD, SMIRNE S. Excessive daytime sleepiness: a 1-year study in an unselected inpatient population. Sleep 1982: 5: 239-247. 5 . PARTINEN M, RIMPELA M. Sleeping habits and sleep disorders in a population of 2016 Finnish adults. Yearbook Health Ed Res 1982. Helsinki: The National Board of Health, 1982: 26: 253-260. 6. LAVIEP. Sleep habits and sleep disturbances in industrial workers in Israel: main findings and some characteristics of workers complaining of excessive daytime sleepiness. Sleep 1981: 4: 147-158.
Daytime sleepiness 7. LUGARESI E, CIRIGNOTTA F, ZUCCONI M et al. Good and poor sleepers: epidemiological survey on the San Marino population. In: GUILLEMINAULT C, LUGARESI E, eds. Sleep/wake disorders: natural history, epidemiology and longterm follow-up. New York: Raven Press, 1983: 1-12. 8. KARACANI, THORNBY JI, WILLIAMS RL. Sleep disturbance in a community survey. In: GUILLEMINAULT C, E, eds. Sleep/wake disorders: natural history, epLUGARESI idemiology and long-term follow-up. New York: Raven Press, 1983: 37-60. 9. HYYPPAMT, KRONHOLM E, eds. How does Finland sleep? Sleeping habits of the Finnish adult population and the re-
habilitation of sleep disturbances. Turku: SOCInsurance Inst, Finland ML: 68, 1987. 10. PARTINEN M. Sleepinghabits and sleep disorders before and after military service (in Finnish). Acta Milit Fenn: Suppl 1. 11. GUILLEMINAULT C, CARSKADON M. Relationship between sleep disorders and daytime complaints. In: KOELLER WP, OEVINPW, eds. Sleep 1976. Basel: S . Karger, 1977: 95-100. 12. BROUGHTON R, GHANEMQ, HIRSHIKAWA Y etal. Life effects of narcolepsy in 180 patients from North America, Asia and Europa compared to matched controls. Can J Neurol Sci 1981: 8: 299-304.
34 1
I
The prevalence of daytime sleepiness and background factors associated with it were investigated in a study carried out at the UKK Institute. The inquiry took the form of a questionnaire mailed to 1600 people of middle age. Daytime sleepiness was found to be associated with disturbed night sleep. Women were more tired than men, but men slept more frequently during the day. Those suffering from tiredness complained of poor health more than other respondents. Traffic accidents and other mishaps attributable to tiredness had occurred in 1.3% of cases, and almost 5 % of male respondents had dozed off while driving at least five times in their lives. The findings indicate a need for increased attention to disturbance of sleep and daytime sleepiness in routine health screening.
The Finnish word “vasymys” may express not only sleepiness but also exhaustion. According to the latest international classification of sleep, sleepiness means difficulty in maintaining an alert waking state, this being divided into three grades of severity. Mild sleepiness manifests itself in states of rest and in tasks requiring for little attentiveness; moderate sleepiness may hamper even slight physical activity and tasks calling for a moderate degree of alertness, as for example driving; in its serious form, sleepiness is manifested daily even in the course of physical activities such as eating and walking, and the detriment to social intercourse and work life is considerable. Fatigue and tiredness, on the other hand, are mentioned as daytime symptoms associated with insomnia (1). In material from the sleep clinics the sleep apnoea syndrome is the most common disorder associated with excessive daytime sleepiness; other illnesses inducing tiredness are narcolepsy, idiopathic hypersomnia and nocturnal myoclonus. Not all daytime sleepiness, however, is attributable to illness. In addition to inadequate night sleep (2), a variety of factors such as shift-work and medication may be the cause. A number of those complaining of tiredness are suffering from more general exhaustion, underlying which is in many cases a state of depression. The purpose of the present study was to ascertain the prevalence of subjectively experienced daytime sleepiness, together with factors associated with it, in an unselected middle-aged urban population. With
K. Martikainen’, J. Hasan’, H. Urponen3, I. Vuori3, M. Partinen4
’
Hatanpaanpuisto Hospital, Tampere University Hospital, UKK Institute, Tampere, Department of Neurology, Kivela Hospital, Helsinki, Finland.
Hatanpaanpuistokuja 8, 33 100 Tampere, Finland Accepted for publication January 15, 1992
an eye to obtaining as comprehensive a picture as possible of the situation, particular attention was paid to the diversity of questions on tiredness and the precision of alternative answers (Table 1).
Table 1. Questions on tiredness and alternative answers Have you felt tired during the daytime within the last three months? Not once Less than once a week One or two days a week Three to five days a week Daily or almost daily How often have you taken a nap during the day within the last three months? Not once Less than once a week One or two days a week Three to five days a week Daily or almost daily Have you felt a compulsive desire to sleep in the course of your ordinaty tasks within the last three months? Not once Less than once a week One or two days a week Three to five days a week Daily or almost daily Several times a day Do you feel that you are generally more tired than your friends and colleagues? Not more tired but clearly more sprightly than they Not more tired but soemwhat more sprightly I find no difference Yes, I am somewhat more tired than they Yes, clearly more tired
331
Martikainen et al. Material and methods
The study was carried out in 1985 at the UKK Institute in Tampere, and took the form of a mailed questionnaire. Subjects were picked by a stratified random sample (N = 1600) of the adult population of Tampere, so structured as to comprise 200 men and 200 women from each of the age groups 36-, 41-, 46- and 50-years. The questionnaire was completed by 1190 people, a response constituting 75.2% of the total sample, 81% (N=641) of women and 69% (N=549) of men. The lowest response percentage (53%) was in the group 41-year-old men ( 3 ) . In addition to completing the questionnaire the subjects kept a record of their sleep for one week. Questions on tiredness and quality of sleep focussed on the three months preceding the time of inquiry. Further questions concerned snoring, general health, medication, stimulants, education, occupation, working hours, living habits - here in particular exercise - and height and weight. The designation "tired" was applied to respondents who considered themselves to be clearly more tired than their acquaintances and colleagues, who experienced daily a compulsive desire to sleep in the course of their normal undertakings, or who felt tired every day. The results of the inquiry are crosstabulated by sex and age. Statistical significance was assessed by the X-square test.
Results Prevalence of tiredness
On the above criteria, a total of 117 (9.8%) people were classified as tired; of these, 38 (32.5%) were men and 89 (67.5%) women. Four of the total, two men and two women, had complained of all the forms of tiredness mentioned. The condition was clearly more common among women; of the women responding to the inquiry 12% were classed as tired, as against 6.9% of the men. On the other hand, men more frequently slept during the day. The material included two narcoleptic patients, both of them women.
Table 2. Tiredness (%I by age and sex ~
~
~
Men (N=549)
Age groups Daytime sleepiness Never More seldom than once a week 1-2 daysa week 3-5daysaweek Daily
Women (N=641I
36 %
41 %
46 %
50 Total 36 % % %
10
12
11
12
11
39 3 1 37 39 31 35 39 30 12 10 9 11 8 6 4 8
38 34 10 7
Compulsion to sleep Never 13 73 6 1 15 72 More seldom than once a week 20 21 24 17 21 1-2 days a week 5 3 6 6 5 3-5 days a week 1 2 2 1 1 Daily or many times a day 1 1 1 1 1 Generally more tired Clearly more alert More alert No difference More tired Clearly more tired
6 4 8 6 8 7 1 3 5 79 82 12 79 6 5 1 9 1 2 - 1
41 46
%
%
5
4
50 Total % %
7
5
35 3 1 39 29 42 40 35 41 5 9 8 11 13 9 1 4 1 2
35 40 8 12
6 1 71
13 66
69
22 19 20 18 6 5 2 1 2 2 3 1 2
20 6 2
5
3
2
4
6
3 8 2 10 9 1 1 78 71 12 16 1 1 6 1 1 3 1 - - 3
8
2
3
8 8 71 1 1
5 10 12 1 1
Overweight
Fig. 1 shows the correlation between tiredness and overweight. Those complaining of tiredness were on the average heavier than others: at least 20% overweight (BMI > 30 kg/m2) was recorded for 2 1% of sufferers, as against only 9.3% of all respondents. Quality of sleep
Twenty-seven questions were devised to elicit data on quality of sleep and factors disturbing it ( 3 ) . On
% iM,
,
60
Age
Reports of tiredness were particularly evenly distributed over the various age groups. The only statistically significant association of age was with daytime sleeping among the men (p = 0.004). Men over 50 were most prone to take a nap during the day, 21 % of them on at least three days a week and 10% daily. The occurrence of the various forms of tiredness is set out in Table 2.
338
40
20
0
...
Men
'
TIRED
Men
Women
Normal + 10% overweight
Approx. 20 X overweight
Fig. 1 . Tiredness and overweight.
ALL
Women Approx. 30 % werweiQhl
Daytime sleepiness Table 3. Subjective assessment of health in tired group and whole material (%) Tired
Table 4. Characteristics of subjects involved in traffic accidents attributable to tiredness
N=15
Total
Men %
Women %
Total %
Men %
Women %
Total %
Good Fairly good Average Rather poor or poor
16 40 32
15 24 47
15 29 42
34 40 23
30 40 26
13
14
14
3
4
3
N
38
89
117
549
641
1190
32 40 25
average, those complaining of tiredness reported all the disturbing factors involved more consistently than did the group as a whole. There were, however, no significant differences in respect of the use of sedatives. Tired subjects were more apt than respondents in general to consider their sleep poor; this applied to 5 % of those reporting tiredness, in contrast to 0.7% of the total. A particularly common disturbance reported by the former was waking during the night, mentioned by 42% of tired subjects as against 18% in the whole material. Subjective state of health
The respondents’ own assessment of their health was elicited with the question: How good do you consider your general state of health to be at the moment? Those complaining of tiredness gave more negative assessments than the average, and the most negative assessments came from those who felt they were more tired than others. Of these, 14% considered their health rather poor and 4% poor, while only 9% felt they were in good health. Of those reporting proneness to fall asleep, 12% considered their health rather poor and 4.9% poor. The health of sufferers compared to that of other respondents is shown in Table 3. Work
Among those reporting tiredness, 2 1 (18 %) were on 2- or 3-shift work or night work, the corresponding figure for the whole material being 13%; 15% of sufferers, again, described their work as irregular, as against 10% of all respondents. Those complaining of a compulsive tendency to doze were more likely than other tired subjects to be totally withdrawn from work life, and none was engaged in night work. Only eight subjects had been reprimanded at work in consequence of tiredness, three of these belonging to this group.
Alcohol consumption over 10 occasions a week Unemployed of absent from work Poor sleep Snores every night Daytime sleepiness 3-5 days in the week Overweight by over 20% Shift-work Tiring medication
n
% 40 40 40 27 27 27 20 20
Driving
Among those in the whole material who drove a car or other vehicle, 15% (173 people) had dozed off at the wheel at least once in their lives. Among the men 4.6% reported at least five such occasions. Traffic accidents or other mishaps attributable to tiredness had occurred to 15 persons, that is, 1.3% (1.8% of the men, 0.3% of the women). Only one of these belonged to the last-described group of tired subjects, but four of them reported tiredness on at least three days in the week, and in three cases the tiring effect of medication was possibly a contributing factor. Other background factors to emerge were nightly snoring, heavy consumption of alcohol, unemployment, shift-work, disturbance to sleep and overweight (Table 4). The proportion of absentees from work was clearly greater than expected in the group involved in accidents as compared to the rest (40% vs 5.8%). Probable causes of tiredness
Judging from the replies to the questionnaire and the sleep log material, the most common cause of tiredness was disturbance of night sleep ( 5 6 % ) . Here, the most frequent disturbing factor was snoring, which in some cases (7/31) also involved irregular breathing with respiratory pauses during sleep. Nightly snoring was reported by 32% of those suffering from tiredness. Other common sources of disturbance to sleep were anxiety and tension, especially in the case of older women various pains, and among young women, their children and pregnancy. Two subjects reported that asthma symptoms broke their sleep, and one subject mentioned the frequent need to relieve himself. Tiredness attributable to psychosocial factors without actual disturbance to sleep troubled 18% of respondents. Among tired subjects, 12% were on shift-work and in 9% the probable reason for tiredness was excessively short night sleep. Diagnosed narcolepsy was the source in 1.7 % of tired subjects (N = 2, 0.17% of all respondents).
Martikainen et al. A number of cases clearly involved several concomitant factors inducing tiredness; subjects suffering from tension and insomnia resorted to sedatives for relief. Shift-work frequently involved disturbed and occasionally curtailed night sleep. The role of alcohol as a source of disturbance to sleep was difficult to ascertain by reason of the inadequacy of answers on alcohol consumption. Discussion
Tiredness may take the form of sleepiness outright, involving a tendency to doze off. On the other hand it may also mean a state of exhaustion. Either case involves detriment to work life and social intercourse. Sleepiness, however, is considered the more dangerous form by reason of the risk of accident, especially in traffic and other situations calling for particular alertness. Figures for the prevalence of daytime sleepiness have varied from 0.5% to 14% (4-9). In a National Pensions Board study (9), 9.3% of the adult population (1099 people aged 29-79 years) reported feeling more tired than their acquaintances. In a questionnaire inquiry conducted by the National Board of Health (2016 people aged 15-64years), 10% of men and 14% of women assessed themselves as more tired than their friends and colleagues, and 3% reported suffering daily or almost daily from a compulsive desire to sleep (5). The type and severity of the daytime sleepiness reported in questionnaire studies are often difficult to assess. Tiredness has not been objectively confirmed in these cases, nor has any closer study been made of background factors possibly contributing to disturbance of night sleep. Daytime sleepiness is a common problem involving detriment to well-being and work efficiency. In most cases it is associated with lack of sleep or deficient quality of sleep. In the present study, tiredness turned out to be a particularly common symptom among people of work age. The figures for prevalence corresponded to those obtained in other Finnish studies. The more specific reasons for tiredness cannot be defined on the basis of the present findings. If, however, the probable causes are judged from answers received, the fact emerges that among subjects complaining of tiredness the majority reported disturbed or curtailed night sleep. Although sleep apnoea is not the most common significant cause of tiredness elicited in a study such as this, the most prominent single group among disturbing factors was nightly snoring. The apnoea syndrome was suspected in seven of the sufferers (6%) on the criterion of loud habitual snoring associated with apnoeas and tiredness. Exhaustion was recorded in 21 cases (18%)
340
among the tired subjects. The predominance of women among sufferers may be due partly to their different life situation but also to their different ways of experiencing and expressing things. In the case of older women an additional factor disturbing night sleep is the menopause. The present observations would indicate that even the forms of tiredness leading to or rendering liable to traffic accidents constitute a significant phenomenon. Over half of those mentioning involvement in accidents as a result of tiredness reported feeling tired many days in the week or snoring every night. The figures for accidents were of the same magnitude as those obtained by Partinen in 1982 (10). In the issuing of driving licenses closer attention should be paid to these considerations than hitherto. Of the clientele of the sleep clinics, the greater proportion of whom suffer specifically from daytime sleepiness, almost half have been involved in motor accidents, and over half have had accidents at work (11, 12). The study and care of daytime sleepiness has in general received scant attention, in spite of the fact that the evergrowing demand for efficiency in work life and the increased volume of motorized traffic emphasize the importance of vigilance. Engagement on work tasks calling for an alert state of mind applies to an increasing proportion of the population, and ever more seldom does merely keeping awake suffice in the discharge of work tasks. If the reasons for symptoms of tiredness cannot be ascertained in basic health service facilities, help can be sought from physicians specializing in disturbances of sleep. Acknowledgement This study was supported by the Yrjb Jahnsson Foundation.
References 1. The International Classification of Sleep Disorders. Diagnostic and coding manual. Am Sleep Disorders Assoc, Rochester, 1990. 2. ROEHRS T, ZORRICK F, SICKLESTEEL J etal. Excessive daytime sleepiness associated with insufficient sleep. Sleep 1983: 6: 319-325. 3. URPONEN H, VUORI I, HASANJ, PARTINEN M. Selfevaluations of factors promoting and disturbing sleep. J SOCMed 1987: 24: 15-27. 4. FRANCESCHI M, ZAMPRONI P, CRIPPAD, SMIRNE S. Excessive daytime sleepiness: a 1-year study in an unselected inpatient population. Sleep 1982: 5: 239-247. 5 . PARTINEN M, RIMPELA M. Sleeping habits and sleep disorders in a population of 2016 Finnish adults. Yearbook Health Ed Res 1982. Helsinki: The National Board of Health, 1982: 26: 253-260. 6. LAVIEP. Sleep habits and sleep disturbances in industrial workers in Israel: main findings and some characteristics of workers complaining of excessive daytime sleepiness. Sleep 1981: 4: 147-158.
Daytime sleepiness 7. LUGARESI E, CIRIGNOTTA F, ZUCCONI M et al. Good and poor sleepers: epidemiological survey on the San Marino population. In: GUILLEMINAULT C, LUGARESI E, eds. Sleep/wake disorders: natural history, epidemiology and longterm follow-up. New York: Raven Press, 1983: 1-12. 8. KARACANI, THORNBY JI, WILLIAMS RL. Sleep disturbance in a community survey. In: GUILLEMINAULT C, E, eds. Sleep/wake disorders: natural history, epLUGARESI idemiology and long-term follow-up. New York: Raven Press, 1983: 37-60. 9. HYYPPAMT, KRONHOLM E, eds. How does Finland sleep? Sleeping habits of the Finnish adult population and the re-
habilitation of sleep disturbances. Turku: SOCInsurance Inst, Finland ML: 68, 1987. 10. PARTINEN M. Sleepinghabits and sleep disorders before and after military service (in Finnish). Acta Milit Fenn: Suppl 1. 11. GUILLEMINAULT C, CARSKADON M. Relationship between sleep disorders and daytime complaints. In: KOELLER WP, OEVINPW, eds. Sleep 1976. Basel: S . Karger, 1977: 95-100. 12. BROUGHTON R, GHANEMQ, HIRSHIKAWA Y etal. Life effects of narcolepsy in 180 patients from North America, Asia and Europa compared to matched controls. Can J Neurol Sci 1981: 8: 299-304.
34 1
