Do Men or Women Need More Sleep? | Dr. Allison Brager & Dr. Andy Galpin

Chromosomal Mechanisms Influencing Sleep Differences Between Men and Women00:00

Andy Galpin: What do we actually know about sleep differences between men and women? What I actually want to know about is chromosomally. When you tease out the hormones, whether it's a polymorphism or some other activity at the level of the genome, how is that actually manipulating, manifesting itself into sleep? Any idea what mechanisms would possibly be there if it's not endocrine?

Allison Brager: In terms of mechanism of action, we know there's differences in sleep pressure. If you unpack the onion, sleep pressure is manifest from increasing levels of extracellular adenosine production within the brain, particularly the basal forebrain, which is a wake-promoting area. If sleep pressure is accumulating quickly, which seems to be the case in biological males by way of the testes-determining gene, then there's more rapid accumulation of extracellular adenosine, and the only way to pay off that increasing sleep pressure is through daytime sleep. With females, it just essentially means the rate of accumulation of sleep pressure is lower, which means that the production of extracellular adenosine would be lower. Now, whether that's been studied, it hasn't, but hypothetically, just knowing with all the myriad of studies around accumulating sleep pressure and extracellular adenosine, we predict that's the mechanism of action.

Andy: That's the closest we can come at this point, right?

Allison: Right.

Sleep Onset Latency and Restorative Sleep Differences01:31

Andy: Is it fair? Is it a trope? I certainly know that it feels like the guys that I know versus the girls that I know, guys fall asleep fast.

Allison: Oh, yes.

Andy: Is that actually been demonstrated? Do we know that?

Allison: Yes. That's been demonstrated, again, in these preclinical transgenic mouse models using the four-core genotype. It's also been demonstrated in human studies. In those studies that were done in the '80s by Terry Lee and Rachel Manber, that's exactly what they found is sleep onset for men is much quicker. Then when you look at time to restorative sleep, so that entry into stage 3 non-REM and then REM sleep, the latency is quicker for females. It might take them longer to fall asleep, but to get that restorative sleep, it's much quicker and then much more efficient across the night.

Evolutionary Reasons for Sleep Differences02:35

Andy: Do we have any teleological or evolutionary guess as to why that setup is there?

Allison: I think it all goes back to child-rearing, right? Who's responsible for children? Men are responsible for propagating children, but women, they are the caretakers. I think these are these built-in neurochemical, neuroanatomical circuits that exist because of relationships between who actually takes care of the child.

Psychology vs. Biology in Sleep Differences and Vigilance03:01

Andy: How much of it is, if you know, psychology versus biology there? The classic thing you'll hear is like, "Oh, women ruminate more. They think about stuff more. They're paying attention," or is it simply any host of cascades haven't kicked off yet? The pressure isn't high enough. Do we have any idea of what-- I'm sure it's both are contributing.

Allison: I think that's the psychological aspect, from my lens, is a part of that biological blueprint. It's because females are going to have greater vigilance across the day. What neurochemically is vigilance? It's increased acetylcholine release and activation of acetylcholine areas of the brain, like the basal forebrain, that are going to lead to that. Again, I see the world from the lens of nature versus nurture. I'm not a very good colleague in departments of psychology.

Andy: You have a degree in psychology.

Allison: I have an undergraduate degree in psychology, but really-

Andy: Neuroscience.

Allison: -it's all neuroscience. I was fortunate enough that I did go to a university that really thrived on its neuroscience curriculum.

Andy: Nonetheless, I heard you're a psychologist, and what I just heard you say was psychology is just misunderstood physiology. I get it. That's what you said.

Allison: I agree. Yes, it is. [laughs]

Andy: Dr. Brager said it. Hold my stamp to that.

Sex Differences in Acetylcholine04:00

Andy: Acetylcholine, is that a total concentration issue that generally is higher, or is it a receptor density, or is it both? Do we have any idea of what are actually the sex differences between acetylcholine?

Allison: That's a good question. The studies that I know exist on sex differences focus on one particular area, which is the basal forebrain. That is the seat of major acetylcholinergic production and release and activation within the brain. Then there's cascading effects on other areas. No, I actually think this is the land of great unknown. There haven't been a lot of studies on sex differences and physiology and behavior. If there were, they were done again in the '80s and '90s-

Andy: Totally.

Allison: You got me curious about going back onto PubMed and Google Scholar and looking this up.

Andy: I mean, the stuff that has been done since then, a lot of it is questionnaires. It is. It's pretty low-fidelity stuff, which is good and helpful.

Allison: You need self-report. With our sleep studies that we do in humans now, we always have an objective endpoint endocrine or even behavioral cognitive measure, but it's always paired with self-report. Sometimes the self-report data is what lends the more interesting findings.

Total Sleep Duration, Waking Differences, and Napping06:05

Andy: Women, men fall asleep differently. We get that. What about total duration and waking-up time? Any sex differences that are notable there?

Allison: I'm happy you asked that because I feel like that data has been taken a little bit too far on social media that women need more sleep than men. There is a difference in total sleep time between men and women that was found again in these studies in the 1980s, and it's about 25 minutes to 30 minutes different. I come from this lens, is that clinically significant? I can't answer that, but I feel like in social media that people have taken that information and have run with it that women need to spend-- I think I saw something recently like because women take this long to fall asleep, they need to be in bed for nine and a half hours versus a guy who falls asleep quickly, they only need to be in bed for eight. I think, at a certain point, that's just going to create anxiety around the act of sleeping that it's going to be more harmful than helpful.

Andy: I assume then also, based on this men nap more than women do.

Allison: Yes, we know that. We know that experimentally, we know that anecdotally, you just look at cultures around the world that have siestas and/or it's adopted and celebrated that people nap during the day, as we know that men in general across cultures are more prone to daytime sleepiness and transgenic mice too.

Trends in Napping and Workplace Stigma07:30

Andy: Yes, name there. Are people napping more or less or the same than we have historically?

Allison: That, I don't know. I feel like, at least in the last 10 years, that stigma around napping has been reduced, I would say. It still exists in the military.

Andy: Of course.

Allison: I don't think it's going away. Actually, my colleagues and I from Walter Reed, we have a paper that we published in the flagship journal of sleep around-- it's called The Stigma of Workplace Napping. We strategically anonymously took quotes from senior leaders in the military, and we were flabbergasted. They were like, "No, if my employees nap, they're lazy. They're not productive." I'm like, "Okay. Just whatever." [chuckles]

Andy: If you enjoyed this clip, you can watch the full episode by clicking here. [music]