Researchers in France studying UK civil servants have suggested that people with a healthier midlife diet are as likely to develop dementia 20 years later.

Published in scientific journal, JAMA, previous research on the links between the diet and dementia risk has shown mixed results. Some observational studies link the treatment to a reduced dementia risk, while others suggest that it has little benefit.

Further research suggests the risk depends on the specific type of diet, and the length of time it’s used.

In this study, researchers followed over 8,000 people in the English civil service – the majority of who were men. From 1985-2017, study participants were asked to self-report their dietary habits. They then looked at their electronic health records to see if they went on to develop dementia.

The team looked to see if there was a link between people with a healthier diet and a dementia diagnosis.

The study highlighted that people’s diet was linked to death rates. But the researchers found that diet quality in midlife was not significantly associated with dementia risk. Although the team also looked at people’s thinking changes, they were unable to assess the link between cognitive performance and dementia.

Dr Sara Imarisio, head of research from Alzheimer’s Research UK said: “This is a well-conducted study that has looked at the long-term relationship between diet and dementia risk. As the diseases that cause dementia develop in the brain over decades, it is important that research into potential risk factors spans a similar time-frame.

“While observational studies like this are good at looking at links between lifestyle and dementia risk, looking at the effect of one lifestyle factor in isolation may not tell the whole story. This research doesn’t tell us whether a healthy diet might affect dementia risk in combination with other aspects of healthy living or for particular people with an increased risk of dementia.

“This research relied on people accurately self-reporting their eating habits and there can be a tendency for people to underestimate unhealthy behaviours in this kind of research. The study also based their results on diagnosis records which don’t reflect the full extent of dementia and often miss people who are in the mild stages.

“While the exact link between diet, brain resilience, cognitive decline and dementia remains unclear, healthy eating is associated with a number of other established dementia risk factors. The best current evidence suggests that controlling blood pressure and cholesterol, and maintaining a healthy weight alongside not smoking, drinking within the recommended limits, and staying mentally and physically active can all help us to maintain a healthy brain as we age.

“It’s important to identify the best approaches to encourage lifestyle change and promote healthy brain ageing to prevent dementia within at-risk populations. Alzheimer’s Research UK is now funding work looking at how we can encourage people at risk of dementia to adopt a Mediterranean-based diet in the hope it will reduce their dementia risk.”