2.5. Primary outcomes

Our three primary outcomes include one from each of the hypothesized mechanisms of action of the choir intervention: cognitive, physical, and psychosocial engagement.

The Trail Making Test (TMT), a test of executive function [24], [25], was used as the primary cognitive outcome. The TMT has two conditions: Part A (connecting 25 numbers in order as quickly as possible) and Part B (connecting 25 numbers and letters, alternating in order as quickly as possible). We limited the time to complete each part to 180 s to reduce testing burden (instead of the traditional 300 s time limit) [26]. Our final measure is the time (seconds) to complete TMT-B minus the time to complete TMT-A, which is an index of executive function that isolates the executive control component of the TMT [27]; higher scores indicate better executive function. For descriptive purposes, we also report the time in seconds to complete parts A and B and the number of correct lines per minute on the TMB-B to take into account participants who were unable to complete TMT-B in the maximum time [28].

The primary physical outcome was a timed test of repeated chair stands, one of several tests on the, a performance-based measure of lower body strength from the Short Physical Performance Battery (SPPB) [29]. We recorded the time in seconds to complete five chair stands with a maximum time allowed of 60 s. The possible range is 0–60 s, and higher scores indicate worse functioning (slower performance). In accordance with published guidelines, we also calculated five categories based on seconds to complete (0 = unable, 1=>16.7 s, 2 = 16.6–13.7 s, 3 = 13.6–11.2 s, and 4=< 11.1 s) [29].

The eight-item Patient Health Questionnaire (PHQ-8) [30] assessed depressive symptoms as the primary psychosocial outcome. Raw scores were used as our primary outcome. The possible range was 0–24, with higher scores indicating more depressive symptoms. The internal-consistency reliability for the entire sample was 0.77. There were some differences by language of interview: Cronbach's alpha was 0.74 for the English speakers and 0.84 for the Spanish speakers. We also report frequencies for the published categories of 1–5 (ranging from no symptoms to severe symptoms) and the percent with a PHQ-8 score > 10, considered to indicate clinically significant depression [30].