Humans Need More Sleep in the Winter: Say What?
时间：2012-10-22 05:18:18
（单词翻译:单击）
Humans Need More Sleep in the Winter: Say What?
During this time of year, it’s hard to not be jealous of the various squirrels, hedgehogs, possums, chipmunks1, bats, skunks2, lemurs, and other small mammals that lower their body temperatures and their metabolisms3 for the winter, napping in their burrows4 until the snow goes away. Bears don’t exactly hibernate5, but they do spend winters in their dens6, napping and caring for newborn cubs7. Even some species of reptiles8 and amphibians9 hibernate, remaining in a sluggish10 torpor11 throughout the winter when there’s not enough heat to raise their body temperatures.
Humans, of course, do not hibernate, but it can feel much more difficult to get out of bed on a
chilly12 winter morning than it does in the height of summer. Some people take this as a welcome sign that being awake during the winter is an
affront13 to nature. Or at the very least, they assume that humans need more sleep during winter. Is that true?
The Straight Talk
We don’t exactly need more sleep during the wintertime, but due to factors beyond our control, we definitely want it.
Humans’ sleep and wake cycles are regulated by light. Light suppresses the production of melatonin by the brain’s pineal
gland14. As daylight fades, the pineal gland produces more melatonin, which causes us to feel sleepy. In the morning, the gland is instructed to stop producing the
hormone15, which aids in waking up. We feel sleepier in the winter because there’s less daylight, hence more melatonin. We wake up when it’s still dark outside, before the pineal gland has been instructed to shut down, and it starts up again long before we’re actually ready to go to bed. That adds up to many
lethargic16 mornings and evenings.
Another dirty trick that makes us want more sleep is that wintertime affords us with prime sleeping conditions. It’s dark outside and the house is cool and still—a perfect recipe for a good night’s sleep. No wonder so many people have trouble leaving bed on a January morning.
Although many people end up waking later and retiring earlier during the cold, dark months, there’s no real biological need for getting extra sleep during the winter. There’s more variation in sleep needs among individuals than there is in a single individual between seasons. That is, some people naturally need more sleep than others need in order to function
optimally17, and that number doesn’t change with the seasons.
Even though our body clock is triggered by light and dark, our sleep needs don’t correspond exactly with the length of the days. Think about it: in Scandinavian countries where there may be only a few hours of light per day in the winter, people don’t suddenly need eighteen or twenty hours of sleep per night. Likewise, in the summer when there are only a few hours of darkness, people aren’t suddenly able to get by on only two or three hours.
The imbalance of light and dark is a prime culprit in the development of
seasonal18 affective
disorder19 (SAD), a wintertime malaise characterized by
fatigue20, depression, and weight gain. Sound familiar? It’s no coincidence that treatment for SAD commonly includes light therapy to
reset21 and regulate the body’s circadian rhythms.
The Takeaway
If you’re already getting your optimum amount of sleep, you don’t need extra just because it’s winter. But if you regularly don’t get enough, feel free to fight the freeze by staying
snug22 in your bed as long as possible.
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