Two epidemiological case-control surveys have linked the age at which, growing up, your home got a refrigerator with your chances of getting Crohn’s Disease later in life. The controls (without Crohn’s) got refrigerators later than the cases (with Crohn’s). This is not one of those data-mining correlations. It was (a) predicted and (b) found in two independent studies.
Crohn’s Disease is much more common in rich countries than poor ones so it was reasonable to examine aspects of lifestyle that distinguish rich and poor countries. In rich countries, the likelihood of having Crohn’s seems to be increasing over time, which is more reason to look for environmental explanations. One of the studies was done in Tehran, where a significant fraction of the population didn’t have a refrigerator when they were born. The control group was patients with irritable bowel syndrome, a curious choice. (The differences might have been larger had they chosen a non-inflammatory digestive problem.) The other study was done in England and used a control group of patients with a non-inflammatory disease.
Refrigerators, of course, retard the growth of bacteria, which I believe everyone needs to eat plenty of (the umami hypothesis). Long ago, “ refrigerator mothers ” — mothers who treated their children with insufficient warmth — were blamed for autism and schizophrenia in their children. Now that it is clear that autism is connected with digestive problems there may be ironic truth in the old claim.