If you have a long memory, you'll recall I discussed work claiming a link between solar radiation and human longevity at the end of last year:
The assumed general mechanism in biology is good, whatever you might think of the rest of the theory; it's essentially covered by the reliability theory of aging - biochemical damage, caused by radiation or otherwise, lowers remaining life expectancy by reducing or destroying the functionality of component parts in the machine that is you.
Some interesting studies are quoted in the article on solar radiation, but it looks very much like a case of having a hammer and seeing nails in everything. It is logical to suppose that demonstrated variations in human longevity and disease by location of birth date in solar and seasonal cycles have something to do with the sun at root - but that certainly doesn't mean that the sun is the direct cause of the biochemical damage that leads to such variations. It might be solar radiation, or it might be one or more differences in other systems caused by variations in solar radiation - diet, weather, hormonal changes, behaviors ... just to rattle off a few. There are certainly many more.
I noticed a new paper from the same researchers today, and I thought I'd point your attention in that direction.
This paper reinforces the findings of others regarding the seasonality of various diseases and that there are factors occurring early in utero that increase susceptibility to diseases later in life. The authors use the vital statistics of 320,247 Maine citizens over a 29-year period to show that those born in 3-year peaks of 11-year solar cycles live an average of 1.5 years (CL 1.3-1.7) less than those born in non-peak years. Males are more sensitive than females to this phenomenon, which is statistically demonstrable well into adult life, showing the effect of probable UVR on the early human embryo despite superimposed adult lifetime hazards.
This study also supports the reliability theory of aging which suggests that events affecting the genome early after conception are important in the expression of adult diseases.
Nice to see them giving the nod to reliability theory in this latest work, but it doesn't look like the authors are any closer to demonstrating likelihood of any one mechanism over another.