Young-onset dementia risk increased by Vitamin D deficiency and depression, study says

Vitamin D deficiency, depression and diabetes are among a number of health issues that increase the risk of young-onset dementia, a major study suggests.

The condition - which around 70,000 people in the UK are thought to be living with - is when symptoms of dementia develop before the age of 65.

The study challenges the notion that genetics are the sole cause of the condition, researchers have said.

Targeting the factors they identified could help reduce the risk, they added.

A list of 15 factors - which is similar to that for late-onset dementia - includes alcohol abuse, stroke, social isolation and hearing impairment.

Those with a higher formal education were seen to be at less of a risk.

The study "breaks new ground" and could "herald a new era" for interventions to reduce new cases, said Dr Janice Ranson, one of the study's authors.

The most common feature of dementia is memory loss, but other symptoms include changes in behaviour, and becoming lost in familiar places.

The study, conducted by scientists from the UK and the Netherlands, is the "largest and most robust study of its kind ever conducted", one of it's authors, Professor David Llewellyn, has said.

It looked at data from over 350,000 under-65s from across the UK.

Prof Llewellyn said there was still much to learn but the study "reveals that we may be able to take action to reduce risk of this debilitating condition".

"This pioneering study shines important and much-needed light on factors that can influence the risk of young-onset dementia."

Dr Stevie Hendriks, a researcher at Maastricht University in the Netherlands, said: "Young-onset dementia has a very serious impact, because the people affected usually still have a job, children and a busy life.

"The cause is often assumed to be genetic, but for many people we don't actually know exactly what the cause is. This is why we also wanted to investigate other risk factors in this study."

Meanwhile Dr Leah Mursaleen, the head of clinical research at Alzheimer's Research UK - which co-funded the study - said the results started to fill "an important gap in our knowledge".

"We're witnessing a transformation in understanding of dementia risk and, potentially, how to reduce it on both an individual and societal level," she said.

The study was published in the Jama Neurology journal.