An Interplay between Health Equity and Disparity in Cognitive Decline

Abstract

AbstractBackgroundCognitive decline may be an early indicator of Alzheimer diseases and related dementia (ADRD). To identify the intervention targets that ameliorate disparities in ADRD, it is critical to employ disparity measures that account for health equity. We aimed to investigate disparity estimates in cognitive decline built on three health equity measures.MethodThe study sample (n = 451) was derived from the bi‐ethnic community‐dwelling San Antonio Longitudinal Study of Aging (SALSA). The latent variable mixture model classified cognitive function trajectory strata based on four repeated measures of the Mini Mental Status Examination (MMSE) over 8.5±1.3 years of follow‐up. Three risk adjustments were employed to optimize equity in social determinants of health (SDoH: income, education, social interactions) between Hispanics and non‐Hispanics. 1) Average constrained regression adjustment minimized the impact of SDoH for Hispanics. 2) Covariance constrained adjustment derived estimates with a near independence between the residuals with ethnicity. 3) Net compensation penalized regression imposed a penalty for excess lower MMSE among Hispanics. Inverse propensity score weighting (IPSW) estimates of disparity further adjusted away confounding due to covariates (demographics, disease burdens) between ethnic groups.ResultTable 1 contrasted baseline characteristics of the study sample between Hispanics and non‐Hispanics. Two MMSE trajectory strata were identified: cognitive decline stratum (38%) with mean MMSE decreased from 23.9 to 21.2; and stable cognitive function stratum (62%) with mean MMSE around 28 throughout. Average constrained and covariance constrained risk adjustments attained optimal SDoH equity across three fairness metrics: predictive ratios, fair covariance, and net compensation (Table 2). Ethnic disparity in cognitive decline (Table 3) was strong conditioned on SDoH equity alone (log(aOR) = 4.27, p<0.001). Balancing covariates alone via IPSW without equity in SDoH also fell short for parity (aOR = 1.16, p<0.001). Parity in cognitive decline could be achievable under both SDoH equity and balanced covariates between ethnic groups (aOR = 0.85, p = 0.21).ConclusionOur study suggested that integrating equity metrices in ADRD disparity research could guide the paths to improve equity and reduce disparity. The field would be better served by identifying the causal drivers of disparities through the advancement in equity metrices and mediation analyses that delineate intricate interactions between SDoH and ADRD risk factors.