Hush

Sleeping-beauty

I have been pretty indignant about the fact that while the dude can do his paper-writing-blog-hopping-book-reading routine until the milk boy arrives, and still be chirpy (or at least reasonably presentable) the next (same) day, a single night show leaves me angry, depressed, exhausted and constipated .

Ever since I heard of the wicked witch who cursed the beautiful princess to sleep for a hundred years, I have been wondering if there is a specific gender-connection to sleep. The answers to this question are varied. Most answers come from surveys such as this and this, and at nOnoscience, we tend to be a little skeptical about surveys.

Listed below are some scientific data that I found, which could be used to make some sort of gender-correlation. I would not, however, draw a conclusion from them (there, the disclaimer is in place!), but these are interesting snippets that could be used to justify my midnight yawns to more nocturnal beings I share my blog and life with !

Estrogen

1. The female hormone estrogen is intimately associated with sleep. Menopausal and post-menopausal women have a fall in estrogen levels, that can cause sleep disorders. Extending the logic, women of reproductive age, have an estrogen surge (especially during specific times of their menstrual cycle), (perhaps) resulting in the need to sleep more. A related search on the male hormone testosterone clarified that while testosterone does not cause sleep, the converse holds good. Less sleep lowers testosterone levels in men.

Hypothalamus

2. The hypothalamus, the "health manager" of the human body is the regulator of the sleep cycle. In particular, the "suprachiasmatic nucleus" has been found to be primarily responsible for the circadian cycle. It has been found that the individual neurons of the suprachiasmatic nucleus contain a genetically driven clock mechanism, with a feedback loop that ensures a nearly 24 h cycle. So, how much of sleep you need is probably coded in your genes. Perhaps there is some X-chromosomal gene that predetermines the functional characteristics of the hypothalamus, but with my limited access to published papers, I have not been able to lay my hands on any such published result.

Melatonin2

3. Melatonin is the most widely studied chemical that orchestrates the sleep cycle in mammals. It is a pineal hormone that is secreted in response to light reception by the eye. Of course, it has its own cycle of secretion, independent of light, otherwise visually challenged people would never be able to sleep, but its regularity is mediated by light. Melatonin is believed to slow down muscular activity, by regulating oxygen and the "energetic" hormones away from muscle tissue and other cells. But the most interesting task of melatonin is as the garbage collector of the body ! While the cells are calling it a day, this chemical collects excess free-radicals and other trash that have been generated in the cell, so that the cell is ready for another big day, with a clean sink (I could do with some help with that in my kitchen- but THAT is not quite the gender connection intended!).

From this paper in the Journal of Neural Transmission I learn that the nocturnal melatonin secretion is lowered to a greater extent in women when exposed to light during the night. Now THAT explains why I wake up with the urge to kick some human in the house, who had the light on all night, writing up his blog entry!

Melatonin_sleep

The above figure goes to prove that I need the light switched off at night! [Reproduced from Ref. 1]

Melatonin is derived from "seratonin" the happiness hormone ! Hint ! Hint !

Cry

4. Special biological pigments called cryptochromes, that come in two varieties - CRY1 and CRY2 present in the skin, eye and part of the brain are linked to vitamin B-2, enable animals and humans to synchronize their circadian clock by absorbing blue light and transferring the light signal through the optic nerve to a different part of the brain from the center for vision. It is believed that Seasonal Affective Disorder (SAD), which affects women more than men, could be caused by abnormalities of these cryptochromes either due to Vit B-2 deficiency or genetically-driven defective pigmentation. CRY problems lead to SAD (pun unintended) and sleep patterns in women?

Have there been systematic studies conducted on gender-correlation on sleep and sleep-biochemicals? If so, I would love to hear about them.

Reference

1. P. Monteleone, G. Esposito, A. La Rocca, and M. Maj; J Neural Transm [Gen Sect] (1995) 102:75-80

1. Lakshmi Says:
   November 30th, 1999 at 12:00 am 

   do his paper-writing-blog-hopping-book-reading routine until the milk boy arrives, and still be chirpy (or at least reasonably presentable) the next (same) day, a single night show leaves me angry, depressed, exhausted and constipated . …..Read more here

2. enjay Says:
   December 21st, 2007 at 3:45 am 

   I’m not aware of any gender-based studies on sleep disorders, but thats a great idea for research! Things are opposite in our household, by the way..I’m the nocturnal owl with a smaller sleep requirement! However, the light and dark (and estrogen surges) do seem to affect my sleep cycle much more than they do the resident male’s! I’m going to do some look-up once I get access at work tomorrow! Love your post.