Developing strategies and quality control in the Ageing and Brain Working Study in ELSA-Brasil.

The Ageing and Brain Working Study was linked to ELSA-Brasil, a prospective cohort of 15,105 civil servants aged 35-74 followed since 2008.

• ELSA-Brasil (Estudo Longitudinal de Saúde do Adulto) is a Brazilian Longitudinal Study of Adult Health.
• The cohort has been followed up since 2008.
• Participants were civil servants aged 35-74 years at enrollment.
• The São Paulo investigation center (Centro Investigação São Paulo) was the source of the subsample used in this study.

A representative sample of 2,165 individuals was calculated from 4,566 alive ELSA-Brasil São Paulo participants at the time of sample selection in September 2022.

• The base population consisted of n = 4,566 participants alive at the beginning of sample selection in September 2022.
• The final representative sample comprised 2,165 individuals.
• The sample was divided into two distinct subsamples based on age and cognitive criteria.
• Sample selection began in September 2022.

The first subsample consisted of 1,670 participants under 70 years old in Wave 3, randomized according to cognitive trajectory from Wave 1 to Wave 3.

• Wave 3 was conducted from 2017 to 2019.
• Participants were randomized based on their cognitive trajectory across three waves of data collection.
• This subsample included individuals aged less than 70 years at Wave 3.
• n = 1,670 participants were included in this subsample.

The second subsample was a SuperAgers case-control sample of 495 participants aged 70 or older in Wave 3, defined based on episodic memory performance.

• SuperAgers cases were defined based on late episodic memory performance in Wave 3.
• The subsample included 171 cases and 324 controls.
• Participants were aged ≥ 70 years at Wave 3 (2017-2019).
• Total SuperAgers subsample size was n = 495 participants.

Multiple quality control processes were implemented prior to data collection to ensure standardization and data integrity.

• Processes included selection of data collection instruments, training and certification of teams, and preparation of a manual of definitions and standardized operating procedures.
• Additional processes included pilot studies, data collection logistics, harmonization of imaging protocols, and creation of an anti-noise device.
• The multicenter nature and diversity of measures required effective quality assurance and control protocols.
• Weekly reports and statistical monitoring of the sample were conducted during field activities.

After implementing quality assurance and control processes, final stages of clinical and imaging data collection were conducted with continuous monitoring.

• Field activities were managed with weekly reports.
• Statistical monitoring of the sample was performed continuously.
• Both clinical and imaging data collection were included in the final stages.
• The quality control framework ensured methodological consistency and data integrity at all stages.