It shows rural living appears to be linked to the brain-wasting disease and that people raised in the country, rather than moving there later in life, face the greatest dangers.
The reasons why remain a mystery but researchers who came up with the findings now plan to investigate the cause.
Researcher Dr Tom Russ, from the Alzheimer Scotland Dementia Research Centre at Edinburgh University, said: "We don't really know the mechanism. It could be to do with access to healthcare, exposure to some unknown sub-stance, socioeconomic factors, or a number of other factors. We're currently looking into this question in more detail."
Alzheimer's affects an estimated 820,000 people in Britain, of which 84,000 are in Scotland, and the number is expected to more than double in the next 40 years as the elderly population increases.
Some previous studies have looked at how disease rates vary between urban and rural areas. However, the results have been inconclusive due to different definitions of what constitutes city or country life.
To get a clearer picture, researchers from Edinburgh, the Medical Research Council and University College London pooled the results of dozens of different studies from all over the world going back several decades, a process known as a meta-analysis. Their results, published recently in the International Journal of Epidemiology, showed that being born and brought up in the country more than doubled the risk of Alzheimer's disease later in life. But there was a much smaller increase in risk in other forms of dementia.
The researchers said it is important to identify what might be to blame so that something can be done early on in life to reduce the chances of contracting the incurable condition.
The report comes as Alzheimer Scotland says care services for people with dementia need a radical overhaul.
The charity said many of Scotland's sufferers do not receive the co-ordinated health and social support that is vital to help them live in the community. It added that carers, partners and families of sufferers are also lacking essential support as a result of the current "fragmented" care system.
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