Mediterranean Diet and Cognitive Decline

To the Editor: Dr Féart and colleagues¹ performed a prospective cohort study and concluded that adherence to a Mediterranean diet was associated with slower cognitive decline as assessed by the Mini-Mental State Examination (MMSE). We have a number of concerns about the study.

First, the study participants were not blinded, and using the 24-hour dietary recall introduced potential recall bias because participants might recall differently depending on their disease status.² Second, using MMSE as a scale for assessing cognitive function may not have been an optimal choice. A study using the French versions of the Severe Impairment Battery and MMSE in 69 patients with probable Alzheimer disease concluded that the Severe Impairment Battery was better able to discriminate among patients who had scores lower than 11 points on the MMSE.³ Third, accuracy of the MMSE depends on the educational status of the individual.⁴ Fourth, accuracy of the MMSE has also been shown to vary based on age.⁵