A recent study published in the Nutrients Journal investigated whether changes in body mass index (BMI) were associated with temporal change in cognitive performance in older adults.
Study: Longitudinal examination of body mass index and cognitive function in older adults: The HELIAD study. Image Credit: SewCreamStudio/Shutterstock.com
Cognitive decline and neurodegenerative diseases, including dementia and Alzheimer’s disease, are growing concerns as the population ages.
Statistics indicate that more than 55 million people worldwide suffer from dementia and the number of cases is expected to more than double by 2050.
With no effective treatment options available, solutions largely center on lifestyle management, and current research focuses on identifying and modifying risk factors for cognitive decline, such as obesity. .
Various studies have identified an association between cognitive function and obesity in middle-aged people, with longitudinal studies indicating midlife obesity as a risk factor for dementia.
However, the results of studies on the correlation between obesity and the risk of dementia in the elderly remain contradictory. This could be due to factors such as failure to take into account confounding variables, such as heterogeneity of the study population according to age or inadequate cognitive function tests.
About the study
In the present study, researchers analyzed the association between BMI and temporal changes in cognitive abilities in a cohort of community-dwelling adults over the age of 65.
The association between BMI and cognitive function was analyzed separately for individuals aged 65–75 and those over 75.
Additionally, a comprehensive set of neuropsychological tests were used to assess cognitive function, and researchers adjusted analyzes for potential confounders.
Participants were recruited for the Hellenic Longitudinal Investigation of Aging and Diet (HELIAD) study, which studied the epidemiology of various neuropsychiatric conditions related to aging, such as Alzheimer’s disease, mild cognitive impairment and dementia.
Information on lifestyle and other areas was collected through interviews, with the participation of caregivers whenever necessary.
The height and body weight of the participants were measured to calculate the BMI according to the recommendations of the World Health Organization (WHO). Measurements were taken at baseline and during the first follow-up.
The neuropsychological assessment consisted of a comprehensive set of tests that measured various cognitive domains such as attention and processing speed, verbal and nonverbal memory, executive functioning, visuospatial ability, and language.
Clinical diagnoses of dementia and mild cognitive impairment were determined based on consensus of a team of neurologists and neuropsychologists using established diagnostic criteria.
Depression or depressive symptoms were assessed based on a self-report questionnaire, current medications, and examinations by neurologists.
Demographic data on age, sex, and education level were also collected and blood samples were obtained for apolipoprotein E genotyping to determine genetic predisposition to neurodegenerative diseases.
The results suggest that changes in BMI and obesity are associated with a temporal change in cognitive performance, with the associations changing with age.
For people aged 75 or younger, weight loss from obesity to normal BMI was associated with a lower rate of memory decline, while no change in BMI over three years was not was related to a longitudinal decrease in visuospatial ability.
In contrast, in people over the age of 75, obesity was associated with slower memory decline, and a change in BMI from obesity to normal weight contributed to a more rapid decline in memory domains. attention and processing speed of neurocognitive function.
The authors speculate that the contrast in results for the two groups could be explained by the difference in characteristics of the two age groups, with older people with more comorbidities or chronic conditions being more sensitive to changes such as weight loss. .
Moreover, the paradox of obesity regarding the inverse relationship between obesity and cognitive impairment is explained by the long preclinical phase of dementia.
Weight loss in adults over 75 may result from pathological changes that occur before dementia is diagnosed. Factors such as impaired sense of smell, loss of initiative, predementia apathy and difficulty eating could contribute to weight loss.
Frailty associated with aging could also explain weight loss and cognitive decline due to oxidative stress and inflammation.
Overall, the results suggest that weight loss and temporal decline in cognitive function had a negative association in adults aged 65 to 75.
While in people over 75, obesity was associated with a slower decline in memory, and weight loss was associated with a faster decline in processing ability and attention.