A study that included 131,821 men and women found a lower incidence of cognitive decline and dementia among those who consumed daily coffee or tea. The greatest benefits were observed when individuals in the study consumed two to three cups of coffee or one to two cups of tea per day. No protective effect was found for decaffeinated coffee.¹

Compared with individuals whose intake of coffee was among the lowest 25%, individuals in the study whose intake was among the top 25% had an 18% lower risk of developing dementia. Having an intake of tea that was among the top third was associated with a 14% dementia risk compared with the lowest third. When subjectively reported cognitive decline was analyzed, people whose coffee consumption that was among the top 25% of the study population had a 15% lower risk than those whose intake was among the lowest 25%. Individuals whose tea intake was among the top one-third of the group had a 16% lower risk compared with the lowest third.

"Our analysis revealed that the significant association was exclusive to caffeinated coffee and tea, and no similar association was observed with decaffeinated coffee consumption," the authors affirmed. "This finding suggests that caffeine may be the primary putative neuroprotective agent underlying the observed association."

The study included 45,215 men enrolled in the Health Professionals Follow-up Study, which recruited male health professionals aged 40–75 years beginning in 1986, plus 86,606 women enrolled in the Nurses' Health Study, which enrolled women aged 30–75 starting in 1976. During a 43-year follow-up period, 11,033 cases of dementia occurred. Dietary questionnaires completed at enrollment and every two to four years provided information concerning the intake of coffee and tea. Subjective cognitive function, including memory, attention, executive function and visuospatial skill, was evaluated at several time points. Dementia cases were identified via physician diagnoses or death records.

"When searching for possible dementia prevention tools, we thought something as prevalent as coffee may be a promising dietary intervention—and our unique access to high-quality data through studies that have been going on for more than 40 years allowed us to follow through on that idea," senior author Daniel Wang, MD, ScD, of Harvard Medical School stated. "There are lots of important ways to protect cognitive function as we age. Our study suggests that caffeinated coffee or tea consumption can be one piece of that puzzle."