Long, irregular naps made around noon and early in the afternoon, are associated with higher risk of mortality. This is revealed by American researchers who have analyzed sleep habits of more than 80,000 British seniors aged 63 years at the start of the study.
A napting duration of 40 minutes on average per day
The cohort included exactly 86,565 participants sixty, men (43%) and women (57%). The researchers followed their sleeping habits by activigraphy, an examination which makes it possible to assess the periods of awakening and sleep over several days. The diurnal nap corresponded to the time spent sleeping between 9 a.m. and 7 p.m. The data analysis has shown that the median duration of participants’ naps was 40 minutes a day. The naps were distributed as follows:
- 34% were made between 9 a.m. and 11 a.m.
- 10% were made between 11 a.m. and 1 p.m.;
- 14% were made between 1 p.m. and 3 p.m.;
- 19% were made between 3 p.m. and 5 p.m.;
- 22% were carried out between 5 p.m. and 7 p.m.
The researchers were able to obtain the mortality data of the participants who died thanks to national registers. The study reports that 5,189 participants (6% of the cohort) died during the follow -up period of up to 11 years.
Data analysis has shown that longer naps, greater variability in the duration of dayties and a higher percentage of naps around noon and early afternoon were associated with higher risk of mortality. Note that the results have been adjusted to take into account factors that can increase the risk of mortality, namely the body mass index, smoking, alcohol consumption and the duration of night sleep.
“” “People who slept longer during the day, had irregular diurnal sleep habits or slept more around noon and early afternoon presented an increased risk, even after taking into account factors related to health and lifestyle “, said Chenlu Gao, principal author and postdoctoral researcher at the Massachusetts General Hospital of Boston.
These data contradict current knowledge on naps
Researchers recall that naps of 30 minutes or more can cause a feeling of drowsiness upon waking. This feeling of drowsiness, or “sleep inertia”, can delay the short -term benefits of a nap on performance. On the other hand, short naps (20 to 30 minutes maximum) are more regenerating and can improve vigilance and performance during the day.
“”It is interesting to note that the data showing the risks associated with naps in the middle of the day and in the early afternoon contradict our current knowledge on the nap. Additional research on this link could therefore be necessary “added Gao Chenu.
These results could open the way to taking into account diurnal sleep habits in assessing the risk of mortality in adults.
But beware, if this study suggests a link between long naps and early mortality in seniors, it does not formally establish it, nor explains the mechanisms underlying this possible cause and effect link. In addition, the study presents limits. Analysis of the sleep of the participants was based on the activity, an examination which detects movements, but not brain activity. The calm awakening of the participants could be wrongly classified as sleep. Also, define the diurnal nap as sleep between 9 a.m. and 19 ha could inadvertently include moments of night sleep of the participants, which could affect the precision of the classification.