Is dairy intake associated with cognitive decline/dementia? Original paper

In this meta-analysis of prospective cohort studies, dairy intake was generally not associated with the risk of dementia or cognitive decline.

Whether dairy intake is associated with the risk of (i) combined dementia/cognitive decline, (ii) dementia, or (iii) cognitive decline.

A total of 312,580 participants (average ages of 53–91).

The participants did not have specific health conditions (e.g., type 2 diabetes, high blood pressure, metabolic syndrome) at baseline.

A meta-analysis of 15 prospective cohort studies was performed. Seven studies were conducted in Europe, 6 in Asia, 1 in the United States, and 1 in Australia. The follow-up duration ranged from 4.8 to 30 years. Ten studies assessed cognitive decline (typically measured using the Mini-Mental State Examination), and 5 studies assessed dementia incidence. A variety of dietary questionnaires were used to assess dairy intake. Most (but not all) studies adjusted their results for age, sex, education, physical activity, BMI, disease history, and energy intake.

Data comparing the group with the highest dairy intake to the group with the lowest intake were extracted from each study, and subgroup analyses were performed to determine whether the type of dairy product (milk or cheese), average age of the participants, geographical region, or length of follow-up influenced the results.

Dose-response analyses were also performed to determine whether there was a nonlinear relationship between dairy intake and dementia/cognitive decline.

In analyses that compared groups with higher and lower dairy intakes, no associations were found between dairy intake and the risk of dementia and/or cognitive decline. Subgroup analyses indicated that higher dairy intakes were associated with a reduced risk of dementia/cognitive decline in Asia (−15%), but not in Europe.

The dose-response analysis suggested that dairy intake was associated with a 12% reduced risk of dementia/cognitive decline at an intake of 150 grams per day, above which the association was no longer statistically significant.

A limitation of this meta-analysis was that most studies only conducted analyses for total dairy intake, so there was limited evidence concerning whether certain types of dairy products are better than others for reducing the risk of dementia/cognitive decline. Furthermore, there was insufficient data to be able to conduct analyses according to the fat content of the dairy products.