February 2, 2022

expert reaction to study looking at association between age at onset of multimorbidity and dementia in later life

A study, published in The BMJ, has looked at the association between age at onset of multimorbidity and dementia in later life. 

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 during midlife were more at risk of developing dementia in later life. While this group of volunteers is not reflective of the UK population as a whole, it is a large group that offers valuable insight into the relationship between multiple health conditions in midlife and dementia later in life.

“Large, long-term studies like this are good for highlighting links, but we need research to explore the mechanisms between individual conditions. This insight will enable researchers to design and deliver appropriate interventions that will reduce the number of people who go on to develop dementia.

“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. We do know that it’s never too early or too late in life to take action on brain health and there are things we can do to reduce our risk of dementia. This includes not smoking, only drinking in moderation, staying mentally and physically active, eating a balanced diet, and keeping cholesterol and blood pressure levels in check can all help to keep our brains healthy as we age. Find information and advice on brain health at www.thinkbrainhealth.org.uk”

Prof Paul Morgan, UK Dementia Research Institute Cardiff, Cardiff University, said:

“This is a landmark study of all-causes dementia in the Whitehall II cohort comprising over 10,000 participants at 30 years follow-up. The primary aim of the study is to test whether there is an association of dementia with number of co-morbidities reported for that individual over the thirty year period. Morbidities were selected from a very long list of chronic diseases and participants broadly divided into groups with 0, 1, 2, 3, 4 or 5 co-morbidities at 5-year intervals from 55 to 70 years. Lifestyle factors known to impact risk of dementia, including smoking and exercise, were included as co-variables. The over-arching conclusion is that the number of co-morbidities and their duration (age of onset) are strongly predictive of risk of all-causes dementia.

“The conclusions are interesting but not surprising, anticipated by previous smaller studies in mild cognitive impairment and early dementia. It is frustrating that, because of limitations in the data, the authors elected to use the rather heterogeneous “all causes”, lumping Alzheimer’s disease with vascular dementia and numerous less common causes. It would have been helpful to see a sub-analysis at least for the two commonest causes of dementia.

“The list of co-morbidities is also rather surprising, including several diseases that are well known to be causes of dementia, notably, Parkinson’s disease (removed in sub-analyses) and stroke, but also other neurological and neuropsychiatric disorders linked to neuroinflammation.

“As noted by the authors, the findings add further support to the proposed role of chronic inflammation as a risk factor for and driver of dementia, debated for more than 50 years but now with solid traction in the field. There is abundant evidence that sustained systemic or central inflammation can cause or accelerate neurodegeneration and anti-inflammatory drugs have been suggested as interventions. So, as well as aggressively treating the underling diseases, dampening inflammation in those with multimorbidities might prevent or delay dementia onset.”  

Prof David Curtis, Honorary Professor, UCL Genetics Institute, said:

“I’m not sure how interesting or novel these findings are. We know that some forms of dementia are associated with poor health generally so it seems unsurprising that people with especially poor health should be at increased risk of subsequently developing dementia. The suggestion is that some dementia cases could be prevented if people could achieve better health, although in fact the current study does not actually prove this because it is an observational study.”

‘Association between age at onset of multimorbidity and incidence of dementia: 30 year follow-up in Whitehall II prospective cohort study’ by Céline Ben Hassen et al. was published in The BMJ at 23:30 UK time on Wednesday 2^nd February.

DOI: 10.1136/bmj-2021-068005

Declared interests

Prof Paul Morgan: No conflicts

Prof David Curtis:  I have no conflict of interest.