It's a good idea to take steps early on to prevent dementia. Although we know many of the risk factors associated with it, few treatments are available, so prevention is your best bet. One of those steps could be upping your caffeine consumption, especially if you drink less than two cups of coffee or tea a day.

A recent study by researchers at Harvard and the Massachusetts Institute of Technology used data from two long-term studies that followed tens of thousands of participants for up to 43 years. It found that drinking moderate amounts of caffeinated coffee and tea reduced dementia risk, slowed cognitive decline and helped preserve cognitive function.

People who reported drinking between two and three cups of caffeinated coffee a day had the lowest risk of dementia. Tea drinkers did almost as well.

“When searching for possible dementia prevention tools, we thought something as prevalent as coffee might be a promising dietary intervention,” Daniel Wang, the senior author on the study and an assistant professor at Harvard Medical School and Harvard T.H. Chan School of Public Health, said in a statement, adding that access to data from studies that have been going on for more than 40 years allowed the researchers to follow through on that idea.

The polyphenols and caffeine in coffee and tea have antioxidant and anti-inflammatory effects that could reduce cellular damage and prevent cognitive decline.

Data from 86,600 women enrolled in the Nurses' Health Study and more than 45,200 men enrolled in the Health Professionals Follow-up Study were analyzed. The mean age of participants in the Nurses' Health Study was 46 years old and the mean age of those in the Health Professionals Follow-up Study was 54 years old. Participants did not have cancer, dementia or Parkinson's disease when they enrolled in the studies. More than 11,000 cases of dementia were reported among the almost 132,000 participants during the follow-up period.

Participants in these big, long-term studies filled out a food questionnaire every two to four years. Their responses also enabled researchers to distinguish between coffee and tea and decaffeinated coffee consumption.

Decaffeinated coffee was not found to have any effect on dementia risk and cognitive function, the researchers noted. This suggests that caffeine may be the primary compound associated with these neuroprotective effects, but there may be another reason for this finding. It is possible that people drink decaffeinated coffee because of an underlying health condition that also predisposes them to cognitive decline, Yu Zhang, lead author on the study, told TheDoctor.

Drinking moderate amounts of caffeinated coffee and tea reduced dementia risk. Decaffeinated coffee was not found to have any effect on dementia risk and cognitive function.

People who reported drinking between two and three cups of caffeinated coffee a day had the lowest risk of dementia. They had an 18 percent lower risk than those who did not drink caffeinated coffee. Drinking more than two to three cups a day did not further reduce dementia risk.

Almost eight percent of caffeinated coffee drinkers self-reported cognitive decline or thought that their memory was slipping, compared to more than nine percent of those who did not drink caffeinated coffee.

People in the studies who drank at least one cup of caffeinated tea a day had about a 15 percent lower risk of dementia and better performance on tests of cognitive function than those who drank less.

More than 17,000 women participating in the Nurses' Health Study who were over 70 years old also occasionally completed objective tests of cognitive function. Those who drank caffeinated coffee did better on those tests than those who did not.

Going forward, Zhang, a PhD student at the Harvard T.H. Chan School of Public Health, said the researchers hope to take a closer look at the factors, such as metabolites in the blood, that drive these effects.

The study is published in JAMA: The Journal of the American Medical Medical Association.