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Illustration of a trees losing its leaves to represent progression of dementia

Research led by Oxford Population Health, and the Albertinen Haus Centre for Geriatrics and Gerontology, University of Hamburg, has found that living with two or more health conditions was associated with a 63% increased risk of developing dementia. The researchers used data from more than 200,000 UK Biobank participants.

It has long been considered that a diverse range of individual health conditions increase the risk of dementia. This includes high blood pressure, diabetes, stroke, depression and possibly even hearing impairment. However, more than a third of people live with two or more conditions, and this increases to two-thirds by the time people reach their 60s. 

The study, published by the Journal of the American Medical Association Network Open, aimed to understand how multiple health conditions that commonly co-occur could impact a person’s chances of developing dementia later in life.

All of the study participants were aged 60 or above and had no evidence of dementia at the start of the study. 89,201 (43%) of the participants had two or more health conditions, known as ‘multimorbidity’. The researchers first investigated the association between multimorbidity and dementia, comparing the results to participants with one or zero health conditions. Then the researchers investigated whether there are certain patterns of co-occurring diseases that are specifically linked with a high risk of dementia.  

Of the 206,960 participants, 6,182 went on to develop dementia.

Key findings

  • Multimorbidity was associated with a 63% increased risk of developing dementia over a period of 15 years.
  • The study found that the more health conditions an individual was living with, the greater their risk of dementia;
  • For both women and men, having co-occurring cardiometabolic and cardiovascular diseases, such as hypertension, diabetes, coronary heart disease and stroke, was associated with more than double the risk of dementia. This finding underlines the importance of managing these often co-occurring conditions to reduce dementia risk;
  • Other identified patterns included less well-established risk factors for dementia such as cancer and respiratory diseases and patterns that grouped diseases from multiple organ systems, such as pain, osteoporosis, and dyspepsia in women and pain, dyspepsia, and prostate disorders in men. Future studies are need to gain a better understanding of the role these diseases might play in developing dementia;
  • The study looked at whether having a strong genetic risk of developing dementia made a difference to the findings. Having multiple conditions was still associated with a greater risk of dementia regardless of having a ‘low’ or ‘high’ genetic risk. This was also found for the different patterns of disease. These findings suggest that multimorbidity could play an important role in dementia risk irrespective of an individual’s genetic predisposition to dementia;
  • Participants with multimorbidity were also more likely to be older, women, of non-white ethnicity, have lower educational qualifications, and be from more socioeconomically deprived areas compared to those with no multimorbidity. 

Dr Thomas Littlejohns, Senior Epidemiologist at Oxford Population Health, and joint senior author, said  ‘Several individual health problems are thought to increase dementia risk. But rather than living with a single disease, more and more people are living with multiple chronic conditions. When considering how to reduce the risk of dementia, our findings suggest that focusing on multiple, rather than single, health conditions is important. More work needs to be done to look into whether these associations are causal, but even if they aren’t, then having multiple conditions might be an important early warning sign for a person’s risk of dementia.’

Dr Elżbieta Kuźma, Albertinen Haus Centre for Geriatrics and Gerontology, University of Hamburg, who jointly led the study, said ‘This is one of few studies to analyse disease patterns in relation to dementia risk later in life. There is still a lot to learn in this area, but our findings have important clinical implications as they may help identify those at increased risk of dementia and to develop new targeted interventions.’

Dr Rosa Sancho, Head of Research at Alzheimer’s Research UK, said ‘One in three people born today will go on to develop dementia in their lifetime. Age, genetics, and lifestyle are all risk factors for developing the condition, but we know age is also a major risk factor for the development of other health conditions.

‘In this research, scientists looked at whether people with more than one chronic disease in their 60s were more at risk of developing dementia in later life. Large, long-term studies like this are good for highlighting links, but more research is needed to explore the mechanisms between individual conditions. It is important to properly manage long-term health conditions and people who have concerns about any aspect of their health should speak to their GP.’

The study involved a collaborative network of researchers based at Oxford Population Health, the Albertinen Haus Centre for Geriatrics and Gerontology, University of Hamburg, and the College of Medicine and Health, University of Exeter.