4 ms·

Leonid Gavrilov and Natalia Gavrilova are a good resource for this sort of demography and epidemiology of aging. [1] In particular they have a lot of material o

Leonid Gavrilov and Natalia Gavrilova are a good resource for this sort of demography and epidemiology of aging. [1] In particular they have a lot of material on season of birth effects. [2] Tangentially related to the seasonal effects is data suggesting that solar cycles also influence longevity, possibly through quite indirect responses to levels of UV exposure in pregnant women. [3] You can see how this might be relevant to season as well, but it is only one of a number of mechanistic theories on the subject. This sort of thing ties back in to application of reliability theory to aging [4], wherein to make the models fit the observed data individuals have to be born with a preexisting non-zero damage load. [1]: http://longevity-science.org/ http://longevity-science.org/ [2]: http://longevity-science.org/Season-of-Birth.pdf http://longevity-science.org/Season-of-Birth.pdf [3]: http://rspb.royalsocietypublishing.org/content/282/1801/20142032 http://rspb.royalsocietypublishing.org/content/282/1801/2014... [4]: https://en.wikipedia.org/wiki/Reliability_theory_of_aging_and_longevity https://en.wikipedia.org/wiki/Reliability_theory_of_aging_an...

ekianjo 12y ago
But the data in the post does not seem to be super correlated to seasons. You can see that the decrease in life expectancy occurs way before spring (as soon as February) which is still supposed to be a winter month. So the season link is weak.
- vlasev 12y ago
  I'm thinking it has to do with the continuous day/night cycle. It'll be interesting to see if there are any changes with latitude, in particular, what happens in countries closer to the equator.
  - ekianjo 12y ago
    But is there any rationale behind that anyway ? Do we see people born during summer being usually in poorer health than people born during November-December, let's say ?
jrapdx3 12y ago
The differential exposure to UVB, that is, sunlight, was the first thing I thought of reading this article. It is especially likely among people born in the industrial-era 19th century, at a time before the nature of the link between health and sunlight was clearly identified. Around a hundred years ago, the role of UV in preventing rickets was confirmed. By the 1930's, vitamin D supplementation of foods became widespread, and the most obvious manifestations of deficiency (e.g., rickets) essentially disappeared. Studied intensively since the 1930's numerous effects of D (or lack of it) have been reported, and recently interest has exploded. Increasingly evidence implicates low vitamin D levels in a wide range of conditions, such as autoimmune disorders, cancer, and metabolic disease, that are likely contributors to reduction of life expectancy. Seasonality of vitamin D level is well known. In northern latitudes (>=45th parallel) the nadir occurs around March-April, and the peak is measured on average in September-October. The timing of these fluctuations appears quite congruent with the article's assertions about life expectancy, so it's reasonable to think there is a connection. For anyone interested in vitamin D, I highly recommend this excellent review: http://www.tandfonline.com/doi/full/10.4161/derm.24494 http://www.tandfonline.com/doi/full/10.4161/derm.24494

ekianjo 12y ago

But the data in the post does not seem to be super correlated to seasons. You can see that the decrease in life expectancy occurs way before spring (as soon as February) which is still supposed to be a winter month. So the season link is weak.

vlasev 12y ago
I'm thinking it has to do with the continuous day/night cycle. It'll be interesting to see if there are any changes with latitude, in particular, what happens in countries closer to the equator.
- ekianjo 12y ago
  But is there any rationale behind that anyway ? Do we see people born during summer being usually in poorer health than people born during November-December, let's say ?

jrapdx3 12y ago

The differential exposure to UVB, that is, sunlight, was the first thing I thought of reading this article. It is especially likely among people born in the industrial-era 19th century, at a time before the nature of the link between health and sunlight was clearly identified. Around a hundred years ago, the role of UV in preventing rickets was confirmed. By the 1930's, vitamin D supplementation of foods became widespread, and the most obvious manifestations of deficiency (e.g., rickets) essentially disappeared. Studied intensively since the 1930's numerous effects of D (or lack of it) have been reported, and recently interest has exploded. Increasingly evidence implicates low vitamin D levels in a wide range of conditions, such as autoimmune disorders, cancer, and metabolic disease, that are likely contributors to reduction of life expectancy. Seasonality of vitamin D level is well known. In northern latitudes (>=45th parallel) the nadir occurs around March-April, and the peak is measured on average in September-October. The timing of these fluctuations appears quite congruent with the article's assertions about life expectancy, so it's reasonable to think there is a connection. For anyone interested in vitamin D, I highly recommend this excellent review: http://www.tandfonline.com/doi/full/10.4161/derm.24494 http://www.tandfonline.com/doi/full/10.4161/derm.24494