Why Is Sleep So Important?

I’ve seen social media from doctors and trainers focused on peri/menopausal women’s health, and they have been referring to recent studies saying that women may need 8 to 10 hours of sleep per night to support hormonal regulation. How important is sleep for hormonal regulation? Should I be prioritizing sleep over my strength training in the morning? And I certainly feel different with less than eight hours of sleep, but what’s the actual research?

—Counting Sleeps

One of my favorite developments in the past decade or so is that people have gotten the message that sleep is important. That naturally leads to your question: how much sleep is enough?

Getting enough sleep is important for hormonal regulation but maybe not the hormones most people think of. When we have not slept enough, our body deals with that lack of sleep by stimulating the stress hormone cortisol. Cortisol affects our body in a number of ways. It makes us more insulin-resistant, which leads to increased hunger and carbohydrate craving. It raises our blood pressure and can even increase cholesterol. If cortisol levels are elevated at the right time in our menstrual cycle, it could even disrupt the timing of ovulation and thus our menstrual periods.

In general adults need seven to nine hours of sleep per night. There is no evidence that suggests women need more sleep than men on average to regulate their hormones. In fact, lack of sleep raises cortisol in men and women. And cortisol can affect men’s reproductive hormone levels too, but they don’t have a menstrual cycle, so it is less evident.

What we do know, based on reviews like this one, is that hormonal fluctuations and likely specifically fluctuations in estrogen can affect the quality of our sleep. Dropping estrogen levels at certain times in our menstrual cycle and during perimenopause can lead to sleep disruption and the perception that we are not sleeping well.

If we are not sleeping well, whether it is due to difficulty falling asleep, staying asleep — it is normal to wake once at night to use the bathroom, but it should be relatively easy to get back to sleep — or early waking, we will end up spending more hours in bed to meet our sleep needs. If we sleep poorly a few nights in a row, we will build up sleep pressure and suddenly sleep 9 or 10 hours if our obligations don’t prevent us from doing so.

The takeaway: Sleep is important — not getting enough sleep can raise cortisol levels — but women don’t need more sleep than men on average. Throughout our lives, fluctuations in estrogen levels can lead to increased sleep disruption and the perception that we are sleeping poorly. This can mean we need to spend more time in bed to meet our sleep needs.