I have been noticing a lot of videos recently about the importance of getting
a good night’s sleep for your fertility. Is this true? Is your fertility lower if
you do not get a good night’s sleep? What does a good night’s sleep even mean? Is
this just a trick to get people to buy a fancy sleep tracking watch? Stay tuned.
There are potentially a few different factors to consider when determining what goes into
having a good night’s sleep. First is the total length of time spent sleeping each night. This
is determined, of course, by when you go to bed and when you wake up the next morning but
is also determined by other factors such as how long it takes to fall asleep and
how often and for how long you wake up during the night. A second factor which determines a
good night’s sleep is the amount of time spent in various sleep stages such as light sleep,
deep sleep and REM sleep. Once you lay down and fall asleep, your body will cycle through
these different sleep stages including waking up multiple times during the night.
For example, here is a graph of my sleep cycles from last night from my watch. As you can see,
I spent some time in deep sleep, light sleep, REM sleep and there were multiple
times where I woke up during the night. Importantly, I don’t remember waking up at
all. This is very important. I went to bed at 10:25 p.m. and woke up this morning at
5:53. That’s 7 hours and 28 minutes. But I was not asleep that entire time. If you subtract
the times that I woke up during the night, I actually only got 6 hr and 37 minutes of sleep.
So if a researcher is trying to do a study regarding the impact of sleep on fertility,
what do they measure? There are three techniques: a survey, in which you just ask people questions
like “how long did you sleep last night?” or “do you feel rested today?” This is the easiest method
but is the least accurate way to assess sleep. Next you can have people wear a sleep monitor,
like a watch to measure their movements and heart rate during the night. The
most accurate method measures your brain’s electrical activity as well
as other parameters like your heart rate and breathing rate. This is called polysomnography
Looking at studies about sleep and fertility, we see that they all use the least accurate
method to assess sleep - a questionnaire. The largest and most complete study to date looked
at 6,873 female partners of couples attempting to become pregnant for <6 months. They found
no association between sleep duration during the previous month and their ability to get pregnant.
More recently, a smaller study looked at 250 women with infertility compared to 1500 with
normal fertility. There was no difference in the hours of sleep between the two groups. On the
other hand, about 37% of the infertility group answered “yes” to this question:
“have you ever told a doctor or other health professional that you had trouble sleeping”
whereas only 25% of the fertile group answered yes. So trouble sleeping was reported 7% more
often in a group with infertility. This does not tell us, however, that sleep problems were
the cause of infertility in these couples. In fact, it is likely that the reverse is true,
that the stress of having infertility may have caused them to have sleep problems.
A few studies have found that people diagnosed with PCOS have an increase in some self reported
sleep problems such as short sleep duration, feeling sleepy during the day and snoring compared
to women with unexplained infertility. In these studies, women with unexplained
infertility did not have a higher rate of sleep related problems compared to average women.
There have also been a few studies trying to determine if sleep problems reduce the chance
for IVF success. A study of 656 women undergoing IVF did not find any correlation between sleep
duration and either the number of eggs retrieved or the fertilization rates. A
much larger study of over 7800 women found that those who had good sleep quality on
a questionnaire had a slightly higher live birth rate than those who did not.
After looking in more detail, it was only true for women under the age of
35 who did a fresh embryo transfer. The total duration of sleep did not matter.
Our Infertility TV bottom line is this. The science here is very poor. The duration of
sleep doesn't seem to make any difference at all for your fertility. It is unclear whether sleep
problems interfere with fertility or whether people with infertility are more likely to have
developed sleep problems. Is it worthwhile to try to improve your sleep quality? Sure,
there is no downside. But as far as wondering whether this is interfering
with your ability to get pregnant? Well, I wouldn't lose any sleep over it.