Contracting ailments such as heart disease and diabetes before reaching 55 could heighten the likelihood of developing dementia later in life, according to fresh research. Strokes or the emergence of mental health disorders, including anxiety and depression, between the ages of 55 and 70 may also double the risk, the study suggests.

Researchers at the University of Oxford revealed that as many as 80% of dementia sufferers experience two or more chronic health conditions, yet there remains a “lack of understanding” regarding specific diseases, their timing of onset and their connection to dementia.

The scientists identified “critical time windows” during which particular ailments present the greatest threat to patients. For the research, published in Brain Communications, academics examined data from 282,712 individuals using the UK Biobank and studied patterns across 46 chronic health conditions.

They discovered that cardiac conditions including heart disease and atrial fibrillation, alongside diabetes, occurring before age 55 showed the strongest association with dementia risk.

Nevertheless, between the ages of 55 and 70, mental health disorders such as anxiety and depression, plus conditions like stroke, doubled the dementia risk.

Sana Suri, an associate professor and Oxford Brain Sciences senior fellow, explained: “Although we knew that multimorbidity increased the risk of dementia, it was unclear which combinations of health conditions had the most impact and in what sequence.

“This study has identified how specific illnesses tend to co-exist with each other, and also the critical time windows in which they could pose the greatest risk.”

The research indicates that individuals with conditions like heart disease and diabetes during middle age, subsequently developing stroke and mental health disorders, faced the highest likelihood of dementia onset.

Ms Suri emphasised that the presence of additional ailments should be considered when assessing someone’s dementia risk, potentially informing strategies to minimise danger at particular life stages.

She continued: “This study identified associations between multimorbidity and dementia risk, but we need to understand more about why this happens. We also need to try to replicate the study in more diverse groups of people to ensure the results are representative of the population.

“Future studies could examine whether efforts to manage or prevent cardiovascular problems in early-to-midlife, followed by mental health and neurological disorders when people are in their fifties and sixties, might reduce the risk of dementia.”