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Written by Maurice M. Ohayon, MD, DSc, PhD

 

 Numerous clinical studies, however, have explored:

•  the function of napping in the circadian rhythm (Campbell & Zulley, 1989; Zulley & Campbell, 1985),
•  its possibility in the treatment of narcolepsy (Roehrs et al., 1986; Garma & Marchand, 1994),
•  its effects in adaptating to shift work (Dinges et al., 1988; Chan et al., 1989; Bonnet, 1990; Rosa, 1993) and
•  its role in the sleep of the elderly (Buysse et al., 1993).

Clinical evidence clearly shows that napping increases linearly with age (Tune, 1969; Kronholm & Hyyppa, 1985). This suggests that sleep physiology changes as a function of age: napping is often considered a normal characteristic of aging on a part with other sleep problems, most notably, disrupted sleep (Carskadon et al., 1980).
 

Research

We explored the relationship between naps, sleep/wake schedule, sleep symptoms, sleep and mental disorders in a representative sample of the non-institutionalized German population composed of 2216 women and 1899 men aged 15-99 years.
A telephone interview survey was performed by lay interviewers using the Sleep-EVAL system.

Results

Napping on at least 2 days per week was cited by 22.2% (95% confidence interval: 20.9% to 23.5%) of the sample and increased linearily with age, reaching 53.3% in subjects 75 years of age and over. Presence of daytime sleepiness was positively associated with napping for all age groups. In subjects younger than 65 years, napping was also related to:

•  night or shift working,
•  presence of a physical illness,
•  bipolar disorder,
•  and idiopathic hypersomnia.

In elderly subjects (over 75 years), only the report of daytime sleepiness and primary snoring were related to napping.

The results show that there are numerous differences between nappers and non-nappers within different age groups:

•  The sleep of nappers under 65 is characterized by an irregular sleep-wake schedule, a shorter sleep time, and a longer sleep latency compared with their non-napping counterparts.
•  Similarly, younger nappers present with many pathological symptoms or disorders (e.g., cataplexy-like symptoms and mental disorders) not observed in non-nappers in the same age group.
•  Elderly nappers have higher occurrence of sleep leg disorders (Periodic limb movment disorder, nocturnal leg cramps or restless leg syndrome), insomnia symptoms, use of sleep medication and physicial diseases.
•  Nappers under 65 years of age have a higher occurrence of depressive disorders, feel more often that napping is unrefreshing, and have their night sleep affected by napping. They are also more likely than elderly nappers to have at least one dysomnia and/or mental disorder.

This suggests that the presence of napping in the younger age groups (<65 years of age) is the consequence of lifestyle and/or of pathology, whereas in the elderly, it is explained in part by disruptive events occurring at night, namely, nocturnal awakenings and primary snoring. This last finding was also observed in laboratory studies (Buysse et al., 1992). In the elderly, it appears that good or poor sleep has little impact on the presence of daytime naps. One hypothesis is that there is a decline in the amplitude of the circadian rhythm in the sleep propensity of the elderly (Carskadon et al., 1980, Buysse et al., 1992).
This hypothesis is supported by the fact that bedtime occurs about 30 minutes earlier for the elderly compared with younger subjects and that overall sleep time including naps is comparable across age groups.
 This suggests a redistribution of sleep over a 24-hour period (Kronholm & Hyyppa, 1985; Buysse et al., 1991; Gerard et al., 1978; Hayter, 1983; Gerber et al., 1985; Liberman et al., 1989; Webb, 1982). Another explanation was put forward by Broughton (1989). According to this author, the human sleep/wake rhythm could be a biphasic one with a two per day rhythm of sleep: a main sleep period occurring at night and a napping period in the mid afternoon. However, societal requirements are not designed to respect this biphasic sleep/wake pattern. In fact, industrialization and productivity are not compatible with daytime napping, which is further illustrated in our data by the dramatic increase in the percentage of men who nap once they are retired and by the higher proportion of non workers who nap. Similarly, previous studies (Webb & Aber, 1984) have shown that daytime napping has little effect on the night sleep of the elderly. This is in line with the claims made by the elderly in our study. An alternative explanation is that most elderly persons have little or no life constraints preventing them from napping whenever they feel the urge. This was reported in other studies (Garma & Marchand,1994; Spiegel, 1981) which observed that opportunity is an important factor in napping. This may explain the higher proportion of nappers among retirees, students and the unemployed. However, in the elderly group, other psychosocial factors such as loneliness (Minors et al., 1989; Monk, 1989) and boredom (Webb & Swinburne, 1971) may also affect changes to sleeping habits.

 

Conclusions

 

Is napping a benign lifestyle habit or should physicians take note?

• First, one should consider that most nappers do not have any sleep or mental disorders: about two thirds of the subjects younger than 65 years of age and four out of five among the elderly did not have any sleep or mental disorders in this study.
• However, further examination is required about the age of the subject.

In subjects under 65, the physician should look for other excessive daytime sleepiness symptoms since napping may indicate a sleep disorder of excessive sleepiness that requires medical attention such as narcolepsy or hypersomnia. The sleep quality should also be investigated, especially symptoms of disordered breathing.
Snoring and sleep apnea are likely to produce daytime somnolence.
Investigation of sleep habits is also indicated.
Poor sleep hygiene but also circadian rhythm disturbance may be responsible for daytime napping.
Finally, the possibility of a mental disorder should also be considered.
Among the elderly, napping appears to be a common habit that is reported by about half of this age group. However, it does not exclude the possibility of an underlying sleep disorder especially those likely to deteriorate the quality of sleep such as snoring, restless legs syndrome, and periodic leg movement disorder.

 

More Information

Snoring

"There ain't no way to find out why a snorer can't hear himself snore" Mark Twain (1834-1910)

 

Snoring and Sleep Apnea
Heavy snoring is the most noticeable feature associated with sleep disordered breathing: there is a noted association with hypertension, cerebrovascular accidents and coronary artery diseases

Naps
Epidemiological data in the general population on daytime napping are scarce. This paucity of information reflects a disinterest from epidemiologists probably due to such popular beliefs that napping is a benign lifestyle habit shared mostly by elderly persons or a cultural phenomenon encountered primarily in warm, southern climates.

Normative Sleep Values
Identifying age-related changes in objectively recorded sleep patterns across the human life span in healthy individuals and clarifying if sleep significantly change with age

Adolescents

Despite the inherent importance of sleep there is scant information available on the epidemiology of sleep behaviors and sleep disturbances among youths

 

Country Surveys

 

 

 

 

The STANFORD JOURNAL of SLEEP EPIDEMIOLOGY