People born in the Fall tend to live longer than those born in the Spring. That’s the statistically significant conclusion based on a dataset of over one million people, according to a 2001 paper by James Vaupel of the Max Planck Institute for Demographic Research. Interestingly, the opposite is true for people born in the southern hemisphere
He thinks it may have something to do with the diet of the pregnant mothers, who perhaps eat better (more fresh fruits/vegetables?) in the Summer than in the Winter. But I have an easier explanation: it’s the amount of sunshine.
Sun affects Vitamin D levels, which are clearly linked to all kinds of health. And contrary to what you read, reasonable sun exposure is inversely linked to skin cancer. It’s also possible that sunshine affects the number and type of microbes around, with some “blooming” more in the summer than winter, and maybe that has an affect too.