New study suggests link between autoimmune diseases and dementia

01 March 2017

BMJ: Associations between specific autoimmune diseases and subsequent dementia: retrospective record-linkage cohort study, UK

Researchers from the University of Oxford have found that people admitted to hospital for autoimmune diseases are more likely to later be admitted for dementia, supporting the growing association between the immune system and dementia. The study is published today (1 March 2017) in the BMJ.

Autoimmune diseases are caused by unusual activity of the body’s own immune system. In these diseases the immune system, which usually protects the body from disease, attacks healthy cells in the body by mistake. Previous research has shown that the immune system can behave unusually in dementia and contribute to damage to the brain. The researchers in this study set out to see if there might be a link between the two conditions.

Using hospital admission records in England from 1998 to 2012, the researchers analysed how many people admitted to hospital with an autoimmune disease were later admitted with dementia. During this period, they found that 1.8 million people were admitted with an autoimmune disease and that 81,502 of those people were later admitted for dementia. Compared with a group of 7 million people who went into hospital with other conditions, they found that the people admitted with an autoimmune disease were 20% more like to later be admitted with dementia.

Of the 25 autoimmune diseases that the researchers studied, they found that 18 were associated with dementia, although the number of people with rarer autoimmune diseases was often small. The researchers also looked at the forms of dementia that were reported, finding that there was a 28% increased risk of vascular dementia compared with 6% for Alzheimer’s disease in people previously admitted for an autoimmune disease.

The researchers also looked at the difference between men and women, as many autoimmune diseases are more common in women than men. While 68.6% of all the autoimmune disease cases were women, the risk of a subsequent hospital admission for dementia was higher for men, with a 32% increased risk for men compared with 17% for women.

The time interval between the first admission for an autoimmune disease and subsequent first admission for dementia was taken into account in the analyses. The researchers found that while the associations were generally stronger for shorter time intervals (up to one year), the increased risk of admission for dementia remained over five years after the first admission for an autoimmune disease.

Dr Rosa Sancho, Head of Research at Alzheimer’s Research UK, said:

“We are becoming increasingly aware of the important role the immune system plays in dementia, and this new study provides evidence to support this link. As this study is observational and based only on hospital admission records, we cannot draw firm conclusions from its findings, but it supports ongoing work into the contribution of the immune system to dementia.

“There are 850,000 people living with dementia in the UK and there are as yet no treatments that can slow or stop damage to the brain in diseases like Alzheimer’s. Targeting immune and inflammatory responses is a promising approach for researchers working on new dementia treatments. Alzheimer’s Research UK is supporting projects that are designing new drugs that target different aspects of inflammation as a way to treat Alzheimer’s disease and other forms of dementia.

“The current best evidence for reducing our risk of dementia is that what is good for the heart is good for the head. Not smoking, eating a healthy balanced diet, keeping physically active, drinking in moderation, keeping cholesterol and blood pressure in check, and maintaining a healthy weight are all ways we can reduce our risk of dementia.”