Moderate to severe mid-life anxiety may be linked to dementia in later life, suggests an analysis of the available published evidence in the online journal BMJ Open.
But as yet, it's not clear whether active treatment could curb this risk, and whether non-drug therapies, such as mindfulness and meditation, which are known to reduce anxiety might help, say the researchers.
A mounting body of evidence suggests that mental illness may be associated with dementia in older age, but it's not clear if it represents initial (prodromal) symptoms before the advent of fully fledged disease or if it acts as an independent risk factor.
To probe this further, the researchers trawled research databases for studies looking at the association between mid-life anxiety, in isolation or combined with depression, and the development of dementia.
Only four out of more than 3500 studies met these criteria, but they involved a total of nearly 30,000 people.
All of the studies accounted for a range of potentially influential demographic, physical, and psychological factors, and all found an association between moderate to severe anxiety and future dementia, with a gap of at least 10 years in between diagnoses.
Because the study design differed so much, pooled analysis of the data couldn't be undertaken, but the studies were all of high quality, strengthening the findings, say the researchers.
The findings back up recent evidence pointing to a link between anxiety and risk of mild cognitive impairment, and lend weight to the known association between depression and dementia, they say.
An abnormal stress response, which is typical of moderate to severe anxiety, may speed up brain cell ageing and degenerative changes in the central nervous system, so increasing vulnerability to dementia, they suggest.
"Whether reducing anxiety in middle age would result in reduced risk of dementia remains an open question," they write. But approaches other than anti-anxiety drugs may be worth testing, they say.
"Non-pharmacological therapies, including talking therapies and mindfulness-based interventions and meditation practices, that are known to reduce anxiety in midlife, could have a risk reducing effect, although this is yet to be thoroughly researched," they caution.
But they suggest that given the prevalence of anxiety, it may be worth doctors considering anxiety a risk factor for dementia as well as depression.
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Support for midlife anxiety diagnosis as an independent risk factor for dementia: a systematic review, BMJ Open (2018). DOI: 10.1136/bmjopen-2017-019399