A new study has shown that adults over the age of 65 who are underweight or fluctuate by more than 5 per cent may be more likely to experience more rapid cognitive decline than others. The results of the research by a team from the Department of Nutritional Sciences at Pennsylvania State University were published in the journal Obesity.
“We examined 11 years of data on weight, BMI and waist circumference. Any way we looked at the data, the relationship was crystal clear — the more a person’s weight varied from year to year, the faster that person experienced cognitive decline,” said Muzi Na, associate professor of nutritional sciences and senior author of the study.
The researchers used data from 4,304 participants in the US National Health and Ageing Study between 2011 and 2021. The measurements included tests of memory, orientation and executive function, and were combined into a composite index to measure cognitive performance.
According to the results, people who maintained a stable weight had the lowest rates of cognitive decline, while those whose weight fluctuated the most had two to four times greater rates of decline.
In another analysis, the researchers found that losing 5 per cent or more of weight, or fluctuating between losing and gaining the same amount of weight, was associated with faster cognitive decline. Older adults who only gained weight experienced similar levels of decline to those whose weight remained constant, which does not mean that gaining weight is beneficial, the researchers emphasised.
“Mid-life obesity is a known risk factor for cognitive decline later in life, but there is an ‘obesity paradox,’ associating late-life obesity with a healthier cognitive trajectory,” Na said.
“Some studies have revealed a complex interplay between age-related muscle mass loss and fat gain in older adults, and our study does not suggest older adults should gain weight”.
The team recommended that weight should be continuously monitored as an additional signal to protect cognitive health. But Na emphasised the importance of self-monitoring.
“From one doctor’s appointment to the next, the way weight is measured may not be consistent,” Na said.
“To make sure you understand what is happening to their body and brain, older adults should track their weight at home in a more consistent way. For example, a person could weigh themselves around the same time in the morning after getting up, before breakfast and after a bathroom trip while wearing the same pyjamas. This would provide them with very consistent data.
“Then, if their weight is not stable, they need to let their physicians know”.