Socioeconomic disparities in clinical trials on Alzheimer's disease: a systematic review.

BACKGROUND AND PURPOSE: There is now a wide consensus at recognizing social and economic circumstances as main determinants of an individual's health status. Nevertheless, characteristics relating to socioeconomic status (SES) are poorly described in research reports. The aim of the present review was to verify whether the SES of participants is adequately reported in interventional studies targeting Alzheimer's disease (AD), and to explore the impact of SES proxy measures on the efficacy of the considered medications.

METHODS: A systematic review of available randomized controlled trials (RCTs) on the currently marketed drugs for AD (i.e. cholinesterase inhibitors and memantine) was conducted by performing a structured search on PubMed and the Cochrane databases. The following indicators of SES were considered in the retained studies: (i) educational level, (ii) lifetime job category, (iii) income and (iv) wealth. The study quality was assessed using the Cochrane Risk of Bias Tool for Randomized Controlled Trials.

RESULTS: A total of 48 articles were finally selected. Overall, only eight RCTs reported data concerning the four considered SES indicators. Indeed, only information pertaining to the educational level of participants was provided. Only one RCT (n = 60) performed ad hoc, secondary analyses accounting for the SES of participating subjects.

CONCLUSIONS: The research and clinical relevance of SES has mistakenly been overlooked by the vast majority of RCTs on AD. A greater effort should be made to collect and report data on those SES indicators that may significantly affect the clinical manifestations and trajectories of patients with cognitive disturbances.