Keep naps under 30 minutes—no longer than an hour. If you regularly need a one- or two-hour nap to get through the day, it’s time to see a doctor

People who nap for less than an hour show no increase in mortality or chronic disease risk, and their mental clarity actually improves. In contrast, those who nap for over an hour face roughly a 30% higher risk of coronary heart disease, and about a 20% higher risk of diabetes and obesity. So set that alarm and wake up after half an hour. If you find yourself needing a one- or two-hour nap every day just to function, that’s a clear sign you should get a medical check-up.

Cost

Free. Just set an alarm before you nap; it requires very little willpower.

Benefit

One umbrella meta-analysis compiled data from 16 separate meta-analyses covering 244 health outcomes. An umbrella meta-analysis essentially aggregates findings from multiple existing meta-analyses. Its conclusions: individuals who nap for less than 60 minutes show no rise in overall mortality or chronic disease risk, and experience the greatest improvement in cognitive function (SMD 0.69, 95% CI 0.37–1.00—a reliable range). Naps lasting 20–30 minutes provide the biggest boost to physical performance (SMD 0.99, 95% CI 0.67–1.31). On the other hand, people who nap for over an hour face a roughly 30% higher risk of coronary heart disease, and about a 20% higher risk of diabetes and obesity. Another study used wrist-worn monitors to objectively measure naps in 1,338 adults aged 56 and older, rather than relying on self-reported questionnaires. After up to 19 years of follow-up, 926 participants had died. For every extra hour of napping, mortality risk rose by about 13% (HR 1.13, 95% CI 1.04–1.23). Each additional daily nap added roughly 7% to mortality risk (HR 1.07, 95% CI 1.02–1.13). People who napped in the morning faced a roughly 30% higher risk compared to those who napped earlier in the afternoon (HR 1.30, 95% CI 1.03–1.64).

Notes

This topic remains somewhat controversial. Both of the aforementioned studies merely recorded nap duration without stratifying participants by health status. It’s quite possible that individuals who habitually nap for long periods already suffer from sleep apnea, anemia, hypothyroidism, depression, or other chronic conditions; thus it’s hard to isolate exactly how much of the observed mortality increase is directly attributable to napping itself. Two Mendelian randomization studies involving 453,000 and 541,000 participants respectively found only one consistent link: the more frequently a person naps, the slightly higher their blood pressure and waist circumference become. No causal effect on coronary heart disease or diabetes was detected. Consequently, you shouldn’t view “shortening naps” as a reliable strategy for lowering mortality. The recommendation to “seek medical evaluation” is essentially a Level C suggestion: if daytime fatigue is so severe that you need a lengthy nap, first examine your nighttime sleep quality; be sure to screen for sleep apnea if you snore or experience breathing pauses during sleep, and also run blood tests and thyroid function tests. For tips on how short naps can boost alertness, see Section 3, Item 11 (a 10‑minute nap in the afternoon works wonders). Information on optimal nighttime sleep duration can be found in Section 13 of this chapter (aim for seven hours per night).

Sources · 3

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3. Dashti HS 等 (2021). Genetic determinants of daytime napping and effects on cardiometabolic health. Nature Communications. doi.org/10.1038/s41467-020-20585-3