Three cups of coffee a day keeps the doctor away
The study suggests - for women at least - caffeine could be an ally in warding off the debilitating effects of dementia.
The findings among a group of older women showed self-reported caffeine consumption of more than 261 mg per day was associated with a 36 per cent reduction in the risk of dementia over 10 years of follow-up.
The researchers said the level of caffeine consumption is equivalent to two to three 8-oz cups of coffee per day, five to six 8-oz cups of black tea, or seven to eight 12-ounce cans of cola.
Study lead author Professor Ira Driscoll, of the University of Wisconsin-Milwaukee in the Us, said: "The mounting evidence of caffeine consumption as a potentially protective factor against cognitive impairment is exciting given that caffeine is also an easily modifiable dietary factor with very few contraindications.
"What is unique about this study is that we had an unprecedented opportunity to examine the relationships between caffeine intake and dementia incidence in a large and well-defined, prospectively-studied cohort of women."
Prof Driscoll and her research colleagues used data from 6,467 community-dwelling, post-menopausal women aged 65 or older who reported some level of caffeine consumption.
Their intake was estimated from questions about coffee, tea, and cola drink consumption, including frequency and serving size.
In 10 years or less of follow-up with annual assessments of cognitive function, 388 of the women received a diagnosis of probable dementia or some form of cognitive impairment.
Those who consumed above the median amount of caffeine for the group - with an average intake of 261 mg per day - were diagnosed at a lower rate than those who fell below the median - with an average intake of 64 mg per day.
The researchers adjusted for risk factors such as hormone therapy, age, race, education, body mass index (BMI), sleep quality, depression, hypertension, prior cardiovascular disease, diabetes, smoking, and alcohol consumption.