by Nils Osmar. September 10, 2022. Medical Disclaimer
In the modern world, artificial light makes it easy to set our own hours of waking and sleeping. When this happens, we can find ourselves drifting into life patterns that are at odds with our circadian rhythms. There’s increasing evidence that doing so takes a toll on both our health and longevity.
A recent study called Associations between chronotype, morbidity and mortality in the UK Biobank cohort provides more evidence of this phenomenon.
From the study – emphases are mine:
Greater eveningness, particularly being a definite evening type, was significantly associated with a higher prevalence of all comorbidities.
Comparing definite evening type to definite morning type, the associations were strongest for psychological disorders… followed by diabetes.., neurological disorders … gastrointestinal/abdominal disorders … and respiratory disorders….Compared to definite morning types, definite evening types had significantly increased risk of all-cause mortality …
Mortality risk in evening types may be due to… misalignment between internal physiological timing and externally imposed timing of work and social activities.
I was an evening type for most of my life. I’d crash out around 1 a.m. and get up around 7:30 or 8 in the morning.
When I was researching the factors that might slow down or speed up aging a few years ago, I learned about the elements highlighted in this study.
Growth hormone levels
An additional factor was that there’s a natural spike in human growth hormone that occurs, for most folks around 10:30 or 11 pm. If we’re awake at that time, it doesn’t occur later; we just miss it.
This matters from a longevity viewpoint because we need a healthy baseline level of growth hormone to support the functioning of our thymus glands, which literally atrophy if hGH levels drop too low. See study: Rejuvenation of the Aging Thymus: Growth Hormone- and Ghrelin-Mediated Signaling Pathways
Sleep is one of many factors that effects our hGH secretion (which goes into a steep decline due to the aging process). As described in this 2011 study:
The release of GH is greatly enhanced during sleep, especially early in the night; this is associated with the appearance of delta waves on electroencephalography, which are characteristic of SWS , and increased release of GH-releasing hormone (GHRH) in the hypothalamus
Making the shift
With all of this in mind, I decided to shift to going to bed around 9:30 pm and getting up around 4 or 5 in the morning. Same hours of sleep, just shifting everything earlier. (I had some friends who were in the habit of calling to talk around 10 pm; I had to let them know about the change.)
I thought it might be hard to make the change, but it just took a few nights to make the shift. Getting up earlier made it easier to go to bed earlier. I do notice a tendency in myself toward going to bed around 10:30 instead of 9:30, which I have to correct now and then.
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