Coding the Everyday Discrimination Scale: implications for exposure assessment and associations with hypertension and depression among a cross section of mid-life African American women.

BACKGROUND: Studies suggest that racial discrimination impacts health via biological dysregulation due to continual adaptation to chronic psychosocial stress. Therefore, quantifying chronicity is critical for operationalising the relevant aetiological exposure and hence maximising internal validity. Using one of the most common discrimination scales in the epidemiological literature, we develop a novel approach for more accurately assessing chronicity and compare it with conventional approaches to determine whether coding influences differential exposure classification and associations with hypertension and depression among African American women.
METHODS: Data are from a socioeconomically diverse cross section of 208 mid-life African American women in Northern California (data collection: 2012-2013). Racial discrimination was assessed using the Everyday Discrimination Scale (α=0.95), and was coded using two conventional approaches: (1) situation-based coding: number of different situations ever experienced; (2) frequency-based coding: sum of Likert scale responses ranging from 'never' to 'almost everyday'; and (3) a new chronicity-based coding approach: sum of responses, weighted to capture annual chronicity (eg, 'a few times a month'=3×12=36×/year). Outcomes are hypertension and depressive symptomatology (10-item Center for Epidemiologic Studies-Depression Scale).
FINDINGS: Exposure classification differed by coding approach, by up to 41%. There was a positive association between racial discrimination and hypertension prevalence for chronicity coding only (prevalence ratio=1.61, 95% CI 1.03 to 2.49). For depressive symptoms, a dose-response relationship of similar magnitude was observed for all three coding approaches.
CONCLUSION: Scale coding is an important methodological consideration for valid exposure assessment in epidemiological research. Coding can impact exposure classification and associations with important indicators of African American women's mental and physical health. © Author(s) (or their employer(s)) 2019. No commercial re-use. See rights and permissions. Published by BMJ.