During old age people who grow up in the countryside may be twice as likely to develop Alzheimer's disease as compared to those living in the cities, reveals study.
Researchers from Edinburgh University found that people who were born and brought up in rural areas were at greater risk of the condition than those from towns and cities, the Telegraph reported.
Although the cause of the trend is unclear, the scientists suggested factors like access to health care, or exposure to certain substances in either the countryside or in cities, could have played a role, the report said.
Alzheimer's, a form of dementia, affects more than 800,000 in Britain and the number of sufferers is expected to double by 2050, due to the ageing population, it added.
The researchers studied 51 academic papers containing data on the medical records of 12,580 people from around the world, published over several decades.
Rates of dementia as a whole did not differ greatly between rural and urban dwellers, but for Alzheimer's specifically there was a marked difference, according to the results.
Dr Tom Russ, who led the study, emphasized the difference between the two groups could be down to benefits associated with living with cities, rather than harmful factors linked to the countryside.
"We don't really know the mechanism. It could be to do with access to health care, exposure to some unknown substance, socioeconomic factors, or a number of other factors," he said.
"We're currently looking into this question in more detail," he added.
The findings are published in the International Journal of Epidemiology.