Recent epidemiological surveys revealed that between 23 to 33% of individuals over the age of 65 complain about their sleep (1-6).

Compared to their younger counterparts, elderly:

• spend more time in bed but sleep less (7) and
• have a sleep fragmentation which is more important and is often accompanied with daytime sleepiness (8-10).

Other studies have shown that sleep duration tends to increase with age (11-14). It has been hypothesized that a disturbance in the circadian rhythm might be responsible for the altered sleep patterns observed in some elderly (11, 13, 15-19). According to this hypothesis, the total sleep duration remains the same across the entire life span but its distribution changes during the later years of life: less time is given to night sleep, which is compensated for by napping in the daytime. Still however, other avenues remain to be explored. The changes responsible for this phenomenon could simply be caused by factors such as retirement, decease of the spouse, social isolation, decrease in sensory impulse due to decrease in audition, vision, smell, etc. (20-23).

RESEARCH

This study aimed to explore the relationship the consequences of inactivity and the dissatisfaction with the social life on sleeping habits and insomnia symptoms in the general population. Our hypothesis was based upon the belief that adjustments in changes occurring in life and not age largely contribute to the sleep problems often observed amongst the elderly.

METHODS

The subjects came from three countries: United Kingdom, Germany and Italy. The total sample is composed of 13,057 subjects aged between 15 to 100 years. Elderly subjects (65 years of age or older) represented 18.6% of the sample.

RESULTS

Influence of age on Insomnia

Results of our study confirm our initial hypothesis. Indeed, age alone, after controlling for possible effects of activity and social satisfaction, is not a significant predictive factor for insomnia symptom. These findings indicate that the bidimensional relationship between age and insomnia symptoms can be entirely explained by other factors. In the last years, the linear relationship between aging process and the increase in insomnia symptoms prevalence has been discussed.
For example, in a three-year longitudinal study involving 6,800 elderly, Foley et al (31) concluded that aging process per se was not responsible of incident insomnia. Other factors such as chronic disease, physical disability, depressed mood, poor perceived health, widowhood and use of sedatives explained the incident insomnia. This observation is in line with our finding: healthy elderly (i.e., without physical or mental diseases) has a prevalence of insomnia symptoms similar to that observed in the other age groups.

Influence of inactivity and dissatisfaction with the social life

Furthermore, our results suggest that being active and with a satisfying social life appears to be a protective factor against insomnia symptoms at any age. Other studies also have shown the importance of social engagement in the prevention of cognitive decline in the elderly individuals. In a 12-year longitudinal study involving 2,812 noninstitutionalized persons 65 years of age or older, Bassuk et al (32) observed that social disengagement was significantly associated with a higher probability of cognitive decline at each follow-up period. Conversely, the increase of social engagement was associated with a reduction in the likelihood of cognitive decline.

Daytime activity

Daytime activity was also related to better sleep in elderly by other researchers (12, 33). For example, Habte-Gabr et al (12) found in their elderly sample that social activities (club membership, having a close friend being active in religion involvement) were related to a better sleep quality.

Furthermore, regularity in life-style has been hypothesized to be an adaptive mechanism in age-related changes in the circadian system's sensitivity and therefore, helps to maintain a good health and well-being (34).

Diminished adaptation

However, if poor sleep can be the consequence of declining physical and mental health, declining sleep quality can also be the antecedent to diminished adaptation in the last years of life. For example, Hoch et al (35) found superior sleep quality in a group of very old nuns who had remained engaged in their vocations and who restricted time in bed, as compared with an age-match group of healthy elderly women who were retired, had no religious affiliation and who spent 30-45 minutes longer in bed nightly.

Life adjustments

Life adjustments such as retirement, departure of children from family home, decease of the spouse, etc., can have a great influence on the sleep-wake pattern (20-23). Such major changes often bring a perturbation in the traditional temporal markers. For example, some retirees might neglect the need for keeping a fixed wake up or bedtime schedule. Therefore, these elderly individuals have little or no life constraints that condition their sleep-wake patterns. These observations support our finding that continuing engagement in life, coupled with curtailing time in bed, is associated with preservation of better sleep quality.

Naps

Researchers have also hypothesized that aging may have an influence on biological rhythms as manifested by reduced and fragmented sleep with an apparition of naps to compensate the lack of night sleep among the elderly. Our results show that napping is very different from insomnia symptoms and is not influenced by the activity status nor social life satisfaction.

Physical diseases or chronic illnesses

Sleep can also be modified by other factors such as physical diseases or chronic illnesses which are known to be significant contributors for poor sleep and insomnia symptoms.

This relationship between sleep and health, however, could also be bidirectional. Dew et al (36) observed that inefficient sleep predicted future declines in subjective sleep quality, fewer social activities at follow-up, and higher depressive symptom levels and higher chronic medical burden at one year follow-up.

In our study, we found that physical illnesses and mental disorders are important risk factors for insomnia symptoms and, to a lesser extent, for napping:

• Mental disorders are more frequent among young individuals (less than 45 years of age)
• Physical illnesses are more common in elderly: about one third of elderly reported a physical illness compared with less than 10% in youngsters (15-24 years of age).
• About 20% of subjects before 55 had a mental disorder while this is less than 10% in the elderly.

Mental Disorders

The association between mental disorders and insomnia symptoms has been widely demonstrated in younger populations but has lead to mixed results in geriatric care. However the role of psychological issues on sleep quality in elderly should not be obscured to the favor of other factors such as physical health status. Major life changes experienced with growing old (e.g. retirement or bereavement) also have an impact on insomnia symptoms.

In conclusion, these results illustrate the complexity of insomnia symptoms. Age per se, in healthy individuals, is not a contributing factor for insomnia in the elderly.