Drinking coffee in middle age can decrease the risk of dementia later in life, a new study suggests.

The research, published in the Journal of Alzheimer's Disease, found that those who drink coffee in midlife have a lower risk for late-onset dementia and Alzheimer's disease compared to those who drink little or no coffee.

Researchers found the lowest risk among moderate coffee drinkers, or those who drank three to five cups a day. Their dementia or Alzheimer's risk was lowered by 65 per cent.

While tea drinking did not appear to lower the risk of dementia or Alzheimer's, it did not increase the risk for either condition.

"Given the large amount of coffee consumption globally, the results might have important implications for the prevention of or delaying the onset of dementia or Alzheimer's disease," said lead researcher Miia Kivipelto, of the University of Kuopio, Finland and the Karolinska Institute in Sweden. "The finding needs to be confirmed by other studies, but it opens the possibility that dietary interventions could modify the risk of dementia and Alzheimer's disease."

The findings also suggest that the protective effect of coffee may lead to new treatments for those already diagnosed with either condition.

The study included data from patients who had participated in health surveys throughout the 1970s and 1980s. The average follow-up rate was 21 years.

The researchers decided to study the association between coffee and tea consumption in midlife and the development of late-onset dementia or Alzheimer's "because the long-term impact of caffeine on the central nervous system was still unknown" and because the processes that lead to these conditions may start decades before symptoms appear.

Alzheimer's and dementia are characterized by a number of symptoms that include memory loss, impaired judgment or reasoning, and changes in behaviours and mood.

The study's findings are significant given that recently released figures suggest that as many as 1.3 million Canadians may develop dementia or Alzheimer's disease within the next 25 years.