Scientists have found a link between muscle health and the risk of dementia

Loss of muscle mass, strength, and physical function in sarcopenia is associated with a 42% increased risk of dementia. At the same time, it is impossible to assess the likelihood of developing the disease only by body weight: the association of obesity with dementia differed depending on age. This was reported in the International Journal of Food Sciences and Nutrition (IJFSN).

What is sarcopenia?

Sarcopenia increases the likelihood of falls and fractures, makes it difficult to move and perform daily activities, and in severe cases can lead to loss of independence. At the same time, the condition differs from the usual weight loss: a person can maintain the same body weight or have excess adipose tissue, while losing muscles and physical strength.

Muscle loss and dementia risk

An international team of scientists has studied how sarcopenia, obesity and their combination are associated with the likelihood of developing dementia. To do this, the authors conducted a systematic review and meta—analysis of cohort studies - studies in which the condition of participants was monitored for a certain period of time.

The search covered publications included in the MEDLINE, EMBASE, Cochrane Database and PsycINFO databases from their inception to February 2026. The analysis of sarcopenia included 14 publications, obesity — 72, sarcopenic obesity — four. The researchers evaluated new cases of dementia of all types and its individual forms, and combined the results using a statistical model with random effects.

According to the results, people with sarcopenia had a 42% higher risk of dementia during the follow-up period than participants without the condition. The combined risk ratio was 1.42, with a 95% confidence interval ranging from 1.26 to 1.58. Since the entire interval was above unity, the authors considered the relationship statistically significant.

However, the results do not prove that it is muscle loss that causes dementia. The meta-analysis includes observational studies, so it reveals a statistical relationship, but does not establish a cause-and-effect mechanism. Sarcopenia also cannot be considered an independent diagnostic sign of dementia: it is impossible to determine from the state of the muscles whether a person is developing the disease.

Why age has changed the link between obesity and dementia

A separate part of the work showed that the association of obesity with the risk of dementia depends on the age at which a person's condition was assessed. In participants under the age of 65, obesity was associated with a 9% increased risk. The combined risk ratio was 1.09, and the 95% confidence interval was from 1.01 to 1.16. This is a small but statistically significant relationship.

For people over the age of 65, the result was the opposite: obesity was associated with a 17% lower risk of dementia. The risk ratio was 0.83 with a confidence interval from 0.76 to 0.89.

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However, the corresponding author of the study, Mario Ciervo, professor at the University of Curtin School of Public Health, warned that this result should not be interpreted as a recommendation to gain weight in old age.

One of the reasons for such different results may be the reverse causality. Dementia can develop long before diagnosis, and at the preclinical stage, a person's metabolism, appetite, and body weight may change. In this case, a lower weight immediately before the detection of the disease may not be its cause, but an early consequence of the processes occurring in the body.

This possibility was previously indicated by an analysis of data from 1.3 million people. In it, a high body mass index was associated with an increased risk of dementia when weight was assessed more than 20 years before diagnosis. In contrast, with a shorter follow-up period, a high body mass index appeared to be a protective factor. The authors explained the discrepancy by the fact that weight loss can begin in the preclinical phase of the disease and distort the statistical picture.

Thus, the feedback obtained in the new meta-analysis between obesity after 65 years and dementia does not prove the protective effect of excess weight. It shows how strongly the result may depend on the age of the participants, the duration of observation, and the time when body weight was assessed.

What did the analysis of sarcopenic obesity show?

The researchers also assessed sarcopenic obesity, a condition in which excess adipose tissue is combined with low muscle mass or impaired muscle function. At first glance, such a combination could be associated with a particularly high risk, but the available data proved insufficient for this conclusion.

The corresponding part of the meta-analysis included only four studies. The combined risk ratio was 1.43, but the 95% confidence interval was wide - from 0.87 to 1.99 — and included one. Therefore, the relationship did not reach statistical significance.

The lack of a significant result does not prove that sarcopenic obesity is in no way related to dementia. It means that based on the four available papers, it is impossible to reliably distinguish a possible effect from statistical uncertainty. According to Siervo, more extensive research is needed to track how changes in muscle and fat tissue interact over time.

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How should the results be understood

The main conclusion of the work is not that the risk of dementia can be assessed by weight or appearance. On the contrary, a meta-analysis shows the limitations of this approach. The same body weight may correspond to different ratios of fat and muscle tissue, and the same body mass index may have different values in middle and older age.

Researchers consider it important to maintain muscle strength and function throughout life. According to Burananuxakul, this is facilitated by regular physical activity and proper nutrition. At the same time, it is important to avoid unhealthy weight gain in middle age, since obesity before the age of 65 was associated with an increased risk of dementia in a meta-analysis.

Warren Harding, Chairman and Head of Research and Partnerships at Alzheimer's WA, also drew attention to the practical significance of the results. According to him, the data on muscle mass and strength complement the already well-known recommendations related to physical activity, nutrition, mobility and prevention of falls in old age.