Design and baseline characteristics of the cocoa supplement and multivitamin outcomes study for the Mind: COSMOS-Mind

Large simple trials are potentially efficient and cost-effective approaches to assess interventions to preserve cognitive function in older adults. High-dose cocoa flavanols supplementation is a promising intervention that warrants additional testing. We describe the design, recruitment success, and baseline characteristics of the Cocoa Supplement and Multivitamin Outcomes Study for the Mind (COSMOS-Mind) trial.

COSMOS-Mind is an ancillary study to the large-scale and predominantly mail-based COSMOS randomized controlled clinical trial. COSMOS is assessing whether cocoa extract (including 600 mg/d cocoa flavanols) and a multivitamin reduce risks for major cardiovascular events and total invasive cancer. COSMOS-Mind uses telephone-based interviews to assess cognitive function and impairment to determine whether cocoa flavanols benefit cognitive function in adults aged 65 years or older, targeting the enrollment of 2000 participants to provide >90% statistical power across 3 years of annual follow-up.

Of the 3224 COSMOS screenees who expressed interest in COSMOS-Mind, 2350 (76%) successfully completed baseline cognitive assessments and 2262 (96%) geographically diverse, eligible individuals were ultimately enrolled over one year. At baseline, the primary outcome, a composite of cognitive test scores, was inversely associated with age in a manner consistent with assumptions used in projections of statistical power.

Older adults are willing to enroll in large simple trials that include telephone-based cognitive assessments. Embedding these trials in large studies of other health outcomes is efficient and expands the scientific knowledge gained from the research. ClinicalTrials.gov Identifiers: NCT03035201 (COSMOS-Mind); NCT102422745 (parent COSMOS).