"Did you often go to bed hungry as a child?" Seven in ten older adults in a Chinese survey said yes, and their answers still lined up with a thinking test decades later

Some of the questions in big health surveys are technical. This one was not: "Did you often go to bed hungry as a child?" Researchers in Nanjing took the yes or no answers from people aged 65 to 99 in China and asked whether they lined up with how those same people scored on a thinking test many decades on. The analysis was published on 30 October in the Journal of Global Health.

The data come from the 2017 to 2018 round of the Chinese Longitudinal Healthy Longevity Survey. Of 15,874 people, 9,297 had complete answers on hunger and on the test, the Mini-Mental State Examination. Their average age was 81, and roughly nine in ten were born before 1950. The team set the cut-off by schooling, so that having had little education would not by itself count as impairment. That put 1,108 people in the cognitive impairment group and 8,189 in the comparison group, an after-the-fact comparison known as a case-control design.

Childhood hunger was common in both groups: 76.6% of those with impairment reported it, and 69.5% of those without. Before any adjustment the odds of impairment were 44% higher in people who remembered going to bed hungry. Taking account of birth decade, sex, their own and their parents' schooling, their father's job and the loss of their mother in childhood brought that down to 23% (95% confidence interval 4% to 45%). A second statistical method gave a risk ratio of 1.17 and a difference of about 36 cases per 1,000 older adults, though that figure leans on an assumed population rate of 24.9%, taken from an earlier analysis of the same survey, because this sample's own rate was 11.9%. As a check that did not rely on memory, the team also looked at unusually short arm length or knee height, which can be a lasting trace of poor early nutrition. These were more common in the impairment group too, 19% against 14%.

The caveats are large. Hunger was reported from memory by people some of whom had impaired thinking, and they may recall their early years differently. Anyone whom severe hunger killed young is missing from the survey, which the authors think could make the link look weaker than it is. The test is a screening tool, not a diagnosis. The analysis had no data on when the hunger happened or how long it lasted, and it did not look at adult income or health along the way. One more thing stands out in the paper's own table: the impairment group was about ten years older on average (89.9 against 80.0), and the models adjusted for decade of birth rather than exact age, so some of that gap may remain in the result. The authors call their findings exploratory and say causality is not established. What can be said fairly is narrow, and still worth hearing: a child's empty stomach may be one small part of what shapes the ageing brain, and it is one of the few parts that can be fixed while that child is still a child.