Previous meta-analyses, based on small numbers of heterogeneous studies, have reported coffee consumption to reduce the risk of cognitive disorders.
Researchers Wu et al. attempted to strengthen the evidence related to coffee consumption and cognitive decline with a meta-analysis specific to prospective cohort studies and including a dose-response analysis.
The meta-analysis included nine prospective cohort studies, representing a total of 34,282 participants.
Coffee consumption was assessed at baseline and duration of follow-up ranged from 1.3 to 28 years.
The outcome measure was the incidence of cognitive disorders, including Alzheimer’s disease, dementia, cognitive decline and cognitive impairment.
In the overall pooled analysis, compared with drinking less than one cup of coffee per day, drinking 1-2 cups per day was significantly and inversely related with the occurrence of cognitive disorders (RR=0.82; 95% CI, 0.71-0.94).
In contrast, drinking more than three cups of coffee per day was associated with an increased incidence of cognitive disorders, but the association was not statistically significant.
Dose-response analysis found a J-shaped curve relationship, such that 1-2 cups per day was associated with the lowest incidence of cognitive decline.
This meta-analysis did not evaluate the type of coffee consumed: it did not distinguish between caffeinated or decaffeinated coffee, the type of brewing method or whether the coffee was taken with cream, milk or sugar.
It also did not define the serving size for a “cup” of coffee.
Despite these limitations, this was a well-conducted meta-analysis of prospective cohort studies. The results suggest that moderate consumption of coffee may confer some protection against the incidence of cognitive decline.
