New Delhi, July 30 -- GUANGZHOU - The British children who spent their first years under wartime food rationing never gave much thought to what they were not eating. Seventy years later, they are developing dementia at measurably lower rates than the generation that came after, the one that grew up as postwar shelves refilled with sweets and biscuits and tins of sweetened condensed milk.

That gap is now documented in two studies published Tuesday in the journals Neurology and npj Aging, each independently mining Britain's wartime sugar rationing as a natural experiment in early-life nutrition. Together, they draw the longest longitudinal line yet connecting the sugar a child consumes before age two, or is not exposed to in the womb, with...