New UK research suggests that those with an autoimmune disease may be also be at an increased risk of developing dementia.
The new large-scale, long-term study looked at hospital admissions data, including day cases, from 1998 to 2012 in England.
During this period, more than 1.8 million people were admitted with an autoimmune disease.
The team wanted to find out if admission to hospital with one of 25 autoimmune diseases, including celiac disease, multiple sclerosis (MS), rheumatoid arthritis, and ulcerative colitis, was associated with a increased risk of a future admission to hospital with dementia.
It has been previously been suggested that autoimmune diseases and inflammatory activity may play a part in the development of the condition.
The research showed that when compared to people admitted to hospital for other causes, those admitted with an autoimmune disorder were 20 percent more likely to be admitted subsequently with dementia.
In addition, from the 25 autoimmune diseases included in the study, 18 were significantly associated with dementia, including Addison's disease (48 percent heightened risk); MS (an almost doubling in risk); psoriasis (29 percent heightened risk); and systemic lupus erythematosus (46 percent increased risk).
Although the type of dementia was not always specified, the research did show that the risk was 6 percent higher for Alzheimer's disease, which although small, is consistent with the existing theory that Alzheimer's disease may have an autoimmune component.
The risk was also 28 percent higher for vascular dementia, the second most common type of dementia after Alzheimer's and caused by conditions that block or reduce blood flow to the brain such as a stroke.
The team suggested that the higher risk for vascular dementia might be caused by the association between autoimmune disease and risk factors for cardiovascular and cerebrovascular diseases in general, with those with an autoimmune disease 53 percent more likely to be later admitted to hospital for coronary heart disease and 46 percent more likely to be admitted with a stroke.
Perhaps surprisingly however, those who had previously been admitted to hospital admission for rheumatoid arthritis had a lower risk of being admitted due to dementia, possibly because sufferers are more likely to take non-steroidal anti-inflammatory drugs, such as aspirin and paracetamol, which have been associated with a reduced risk of Alzheimer's disease.
The team also found that men with MS had a significantly higher risk of been admitted with dementia than for women with MS, but for most of the other conditions the risks were similar for both sexes.
However as an observational study no firm conclusions can be made about cause and effect, with the researchers also pointing out that the size of the associations found in the study was small, and results should be taken as indicative rather than definitive, advising that further research is now needed.