This goes to show you what you can discover if you have lots of data.
Vision researchers wanted to test the theory that the development of myopia (nearsightedness) is linked to the amount of sunlight the baby receives in the immediate period following birth. They call it the perinatal photoperiod.
They reviewed the complete health records of over 275,000 children and tracked their refractive errors . Next, they did a statistical analysis of those with myopia using a technique called multivariate logistic regression. Stay awake - here comes the good part!
There were seasonal variations in moderate and severe myopia according to birth month, with prevalence highest for June/July births and lowest for December/January. In the northern hemisphere nearsightedness correlates with sunny birth months. It would be very cool to repeat the study in Sydney or Cape Town to see if such numbers are reversed, just like their seasons.
Remember, this information came from looking at piles of old records, a retrospective study. Retrospective studies are far less meaningful because there can be all kinds of obvious and subtle errors in data gathering that escape detection. For example, was every child in every family enrolled? Did some families opt out and disappear from the database?
Having said that, seasonal associations are a familiar oddity to the practice of medicine. Did you know that
is more likely to occur in the spring? Just last year a different team of researchers reported that you are 27 times more likely to have a heart attack
on your birthday than on any other day of the year. Go figure!