Public Health.

Background: The BetterBrains Trial is a prospective behavior-modification blinded endpoint randomized controlled trial to delay cognitive decline in middle-aged adults (aged 40-70) with a family history of dementia. The primary outcome is absence of decline on at-least one out of four cognitive tests at 24-months. We present trial recruitment and current participant completion statistics and baseline demographic, modifiable dementia risk factor (MDRF) and cognitive characteristics of the randomized sample, blinded to intervention arm.

Method: Participants completed online assessments (betterbrains.org.au), including assessment of vascular, sleep, mood, and social/cognitive engagement MDRFs. Participants with ≥1 MDRF were eligible. Participants also completed assessments of cognition, general health, medical history, and lifestyle factors at baseline, 12- and 24-months. Unsupervised cognitive testing was conducted using the Cogstate Brief Battery (see Figure 2 for details). Subjective cognition was assessed using a modified Cognitive Function Instrument.

Result: From August 2021 to July 2023, 1830 participants enrolled and 1053 (57%) were randomized (Figure 1). Randomized participants were on average 59.7 (±6.8) years, 83% women, 90% highly educated (≥12 years of education), 93% White, and 86% reported a first-degree family history of dementia (Table 1). Importantly, 27% resided in regional or rural Australia (Table 1). Participants reported an average of 6.5 MDRFs (max = 18) and a mean Cardiovascular Risk Factors, Aging and Incidence of Dementia risk score (without APOE) of 6.3 (max = 15) (Table 1). Baseline cognitive performance scores are presented in Table 1 and Figure 2. Randomized participants required, on average, 19.2 days to complete baseline assessment. To date, 61% and 70% of randomized participants have completed the 12- and 24-month assessments (respectively), with study attrition at 3% (Figure 1).

Conclusion: Compared to the general population, participants in this decentralised trial exhibit some increased risk of dementia, indicated by high prevalence of first-degree dementia family history, female gender, and prevalent MDRFs. Participant characteristics are similar to those observed within other lifestyle intervention trials. The finding that 27% of the sample resides in a regional or rural area highlights that the BetterBrains methodology facilitates inclusion of hard-to-reach populations. Low attrition and high follow-up rates suggest that the BetterBrains program is acceptable and feasible.