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reference
Campbell SS, Stanchina MD, Schlagang JR, Murphy PJ. Effects of a month-long napping program in the elderly.J Am Geriatric Soc. 2011;59:224-232.
design
Open-label observational study with 3 sleep sessions in the laboratory and 2 weeks of home recordings in between. Comparing 45-minute (short naps) versus 2-hour (long naps) times on nighttime sleep and wakefulness over a month. Adherence to such a nap program was also assessed.
Participant
22 participants (11 men, 11 women) aged 50 to 83 years (mean = 70 years). Although recruitment was open to individuals without sleep problems, all subjects reported age-related sleep disturbances in the maintenance or duration of sleep. None of the subjects had obvious sleep disorders (e.g. apnea, restless legs syndrome, circadian rhythm sleep disorder) as this was used as an exclusion criterion. Participants did not take a regular nap at the time of enrollment.
Target parameters
Objective and subjective measures were used to assess participants, including polysomnography (sleep EEG), actigraphy, sleep diaries, neurobehavioral performance, and sleep latency testing.
Key findings
Combined, both the short and long nap groups averaged more than 5 naps per week, although there were large individual differences. The nap had no impact on nighttime sleep. For both groups, the average nighttime sleep duration on nap days was 7:57 ± 1:22 hours, compared to 8:06 ± 1:49 hours on non-nap days. Sleep quality (i.e., sleep onset latency, sleep efficiency, sleep architecture) remained unchanged by napping in both groups. Neurobehavioral performance improved in both groups on 3 of 4 tasks measured. Finally, there was an increase in total 24-hour sleep time and a resulting decrease in daytime sleepiness in both groups compared to individual baseline values. Compliance was more favorable in the short nap group than in the long nap group.
Effects on practice
A nap is a custom in many cultures around the world. Whether such naps affect nighttime sleep patterns by shortening the duration or quality of nighttime sleep has been debated. This study suggests that the duration and quality of nighttime sleep is not affected by regular naps. This is consistent with a 2005 paper by the same authors showing that the amount of sleep in a 24-hour period can be improved by adding a daytime nap and that this can improve waking function.1While naps are not a cultural norm in America, there are numerous studies showing that naps, particularly in older people, can improve overall functioning.2,3,4
The authors postulate that the stress-relieving properties of napping may play a role and that working men may benefit more from it due to greater stress reduction.
Other studies have shown that naps can have a greater impact than just improving everyday functional performance. Dr. Androniki Naska studied 23,681 Greek men and women (aged 20-86) and found that people who napped had a 34% lower risk of dying from heart disease than those who didn't nap over more than six years of follow-up. This difference was greatest among working men who napped, with a 64% lower risk of dying from heart disease, compared to a 36% decrease among non-working men.5The authors postulate that the stress-relieving properties of napping may play a role and that working men may benefit more from it due to greater stress reduction.
While the majority of studies on daytime napping have found positive results, some have questioned whether naps are generally beneficial. In a fairly large study of 8,101 Caucasian women (<69 years old) followed over a seven-year period, women who reported napping daily were 44% more likely to die from any cause and 58% more likely to die from cardiovascular causes than women who did not nap.6In the same study, women who reported sleeping 9-10 hours in a 24-hour period had a higher risk of all-cause mortality than women who slept 8-9 hours. Notably, these correlations were not significant when weekly naps totaled less than 3 hours, suggesting that there is no correlation for very short naps. There was no indication whether psychological factors such as depression were included in the study.
A community-based study conducted in Guangzhou, China showed a link between daytime naps and the development of type 2 diabetes. The participants, 19,567 Chinese men and women, completed a questionnaire about nap frequency. Diabetes was assessed by blood glucose levels or reports of a doctor-prescribed diagnosis or treatment. Those who reported napping four to six times a week had a 42% higher risk of developing type 2 diabetes, and those who reported napping daily had a 52% higher risk. This connection has also been found between napping and impaired glucose utilization. Adjustments for confounding factors such as demographics, lifestyle and sleep habits, health status, obesity and metabolic markers did not change the significance of the association.7Whether these data can be generalized to other, more heterogeneous genetic populations remains unknown. However, elucidation of this association should be pursued as the prevalence of type 2 diabetes is increasing rapidly in China.
Of course, link and cause are not the same, and although the observational studies showing possible harm should be taken into account, possible underlying factors, such as genetic predisposition or increased napping in people with depression, may not have been taken into account. Nonetheless, it appears that shorter nap and nap durations in otherwise healthy individuals (i.e., without an overt diagnosis of sleep deprivation) are safe and potentially beneficial for our patients. A warning for people of Chinese descent is prudent, and perhaps maintaining a “normal” total number of hours of 8 hours of total sleep per 24-hour cycle can reduce any possible risk for our postmenopausal population.
restrictions
In the study, it is possible that the improved neurobehavioral performance in both groups was due to repeated exposure to the tests, as there was little correlation with 24-hour sleep times. Because this study only lasted one month, it is possible that further improvements or different results may be achieved over a longer period of time. Of course, none of these participants had obvious sleep disorders, so extrapolation of these data to patients with sleep disorders cannot be made. This study was small - only 22 subjects - so repeating such a study on a larger scale would be necessary to support these results.