Effect modification and interaction between ethnicity and socioeconomic factors in severe COVID-19: analyses of linked national data for Scotland

Ronan McCabe; Eliud Kibuchi; Sarah Amele; Patricia Irizar; Aziz Sheikh; Karen Jeffrey; Igor Ruden; Colin R Simpson; Colin McCowan; Lewis Ritchie; Chris Robertson; Alastair H Leyland; Evangelia Demou; Anna Pearce; Srinivasa Vittal Katikireddi

doi:10.1136/bmjopen-2024-092727

Effect modification and interaction between ethnicity and socioeconomic factors in severe COVID-19: analyses of linked national data for Scotland

Ronan McCabe^*, Eliud Kibuchi, Sarah Amele, Patricia Irizar, Aziz Sheikh, Karen Jeffrey, Igor Ruden, Colin R Simpson, Colin McCowan, Lewis Ritchie, Chris Robertson, Alastair H Leyland, Evangelia Demou, Anna Pearce, Srinivasa Vittal Katikireddi

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

Abstract

Objective: Minority ethnic groups disproportionately experienced adverse COVID-19 outcomes, partly a consequence of disproportionate exposure to socioeconomic disadvantage and high-risk occupations. We examined whether minority ethnic groups were also disproportionately vulnerable to the consequences of socioeconomic disadvantage and high-risk occupations in Scotland. Design: We investigated effect modification and interaction between area deprivation, education and occupational risk and ethnicity (assessed as both a binary white vs non-white variable and a multi-category variable) in relation to severe COVID-19 (hospitalisation or death). We used electronic health records linked to the 2011 census and Cox proportional hazards models, adjusting for age, sex and health board. We were principally concerned with additive interactions as a measure of vulnerability, estimated as the relative excess risk due to interaction (RERI). Results: Analyses considered 3 730 837 individuals aged ≥16 years (with narrower age ranges for analyses focused on education and occupation). Severe COVID-19 risk was typically higher for minority ethnic groups and disadvantaged socioeconomic groups, but additive interactions were not consistent. For example, non-white ethnicity and highest deprivation level experienced elevated risk ((HR=2.7, 95% CI: 2.4, 3.2) compared with the white least deprived group. Additive interaction was not present (RERI=−0.1, 95% CI: −0.4, 0.2), this risk being less than the sum of risks of white ethnicity/highest deprivation level (HR=2.4, 95% CI: 2.3, 2.5) and non-white ethnicity/lowest deprivation level (1.4, 95% CI: 1.2, 1.7). Similarly, non-white ethnicity/no degree education (HR=2.5, 95% CI: 2.2, 2.7; RERI=−0.1, 95% CI: −0.4, 0.2) and non-white ethnicity/high-risk occupation (RERI=0.3, 95% CI: −0.2, 0.8) did not experience greater than additive risk. No clear evidence of effect modification was identified when using the multicategory ethnicity variable or on the multiplicative scale either. Conclusion: We found no definitive evidence that minority ethnic groups were more vulnerable to the effect of social disadvantage on the risk of severe COVID-19.

Original language	English
Article number	e092727
Journal	BMJ open
Volume	15
Issue number	4
DOIs	https://doi.org/10.1136/bmjopen-2024-092727
Publication status	Published - 14 Apr 2025

Funding

This work was supported by the Economic and Social Research Council (grant number ES/W000849/1) and the Medical Research Council (MC_PC_19075). The funders had no role in the study design, data collection and analysis, decision to publish or preparation of the manuscript. RM, SA, EK, ED, AHL, AP and SVK are supported by the Medical Research Council (MC_UU_00022/2) and the Scottish Government Chief Scientist Office (SPHSU17). SVK acknowledges funding from an NRS Senior Clinical Fellowship (SCAF/15/02), the Medical Research Council (MC_UU_00022/2) and the Scottish Government Chief Scientist Office (SPHSU17). AP acknowledges funding from Wellcome Trust (205412/Z/16/Z).

Keywords

COVID-19
EPIDEMIOLOGY
EPIDEMIOLOGIC STUDIES

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

Access to Document

10.1136/bmjopen-2024-092727Licence: CC BY 4.0

McCabe-etal-2025-Effect-modification-and-interaction-between-ethnicity-and-socioeconomic-factors-in-severe-COVID-19Final published version, 919 KBLicence: CC BY 4.0

Cite this

McCabe, R., Kibuchi, E., Amele, S., Irizar, P., Sheikh, A., Jeffrey, K., Ruden, I., Simpson, C. R., McCowan, C., Ritchie, L., Robertson, C., Leyland, A. H., Demou, E., Pearce, A., & Katikireddi, S. V. (2025). Effect modification and interaction between ethnicity and socioeconomic factors in severe COVID-19: analyses of linked national data for Scotland. BMJ open, 15(4), Article e092727. https://doi.org/10.1136/bmjopen-2024-092727

@article{fab1d71120574b9692b5a84924779502,

title = "Effect modification and interaction between ethnicity and socioeconomic factors in severe COVID-19: analyses of linked national data for Scotland",

abstract = "Objective: Minority ethnic groups disproportionately experienced adverse COVID-19 outcomes, partly a consequence of disproportionate exposure to socioeconomic disadvantage and high-risk occupations. We examined whether minority ethnic groups were also disproportionately vulnerable to the consequences of socioeconomic disadvantage and high-risk occupations in Scotland. Design: We investigated effect modification and interaction between area deprivation, education and occupational risk and ethnicity (assessed as both a binary white vs non-white variable and a multi-category variable) in relation to severe COVID-19 (hospitalisation or death). We used electronic health records linked to the 2011 census and Cox proportional hazards models, adjusting for age, sex and health board. We were principally concerned with additive interactions as a measure of vulnerability, estimated as the relative excess risk due to interaction (RERI). Results: Analyses considered 3 730 837 individuals aged ≥16 years (with narrower age ranges for analyses focused on education and occupation). Severe COVID-19 risk was typically higher for minority ethnic groups and disadvantaged socioeconomic groups, but additive interactions were not consistent. For example, non-white ethnicity and highest deprivation level experienced elevated risk ((HR=2.7, 95% CI: 2.4, 3.2) compared with the white least deprived group. Additive interaction was not present (RERI=−0.1, 95% CI: −0.4, 0.2), this risk being less than the sum of risks of white ethnicity/highest deprivation level (HR=2.4, 95% CI: 2.3, 2.5) and non-white ethnicity/lowest deprivation level (1.4, 95% CI: 1.2, 1.7). Similarly, non-white ethnicity/no degree education (HR=2.5, 95% CI: 2.2, 2.7; RERI=−0.1, 95% CI: −0.4, 0.2) and non-white ethnicity/high-risk occupation (RERI=0.3, 95% CI: −0.2, 0.8) did not experience greater than additive risk. No clear evidence of effect modification was identified when using the multicategory ethnicity variable or on the multiplicative scale either. Conclusion: We found no definitive evidence that minority ethnic groups were more vulnerable to the effect of social disadvantage on the risk of severe COVID-19.",

keywords = "COVID-19, EPIDEMIOLOGY, EPIDEMIOLOGIC STUDIES",

author = "Ronan McCabe and Eliud Kibuchi and Sarah Amele and Patricia Irizar and Aziz Sheikh and Karen Jeffrey and Igor Ruden and Simpson, {Colin R} and Colin McCowan and Lewis Ritchie and Chris Robertson and Leyland, {Alastair H} and Evangelia Demou and Anna Pearce and Katikireddi, {Srinivasa Vittal}",

year = "2025",

month = apr,

day = "14",

doi = "10.1136/bmjopen-2024-092727",

language = "English",

volume = "15",

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McCabe, R, Kibuchi, E, Amele, S, Irizar, P, Sheikh, A, Jeffrey, K, Ruden, I, Simpson, CR, McCowan, C, Ritchie, L, Robertson, C, Leyland, AH, Demou, E, Pearce, A & Katikireddi, SV 2025, 'Effect modification and interaction between ethnicity and socioeconomic factors in severe COVID-19: analyses of linked national data for Scotland', BMJ open, vol. 15, no. 4, e092727. https://doi.org/10.1136/bmjopen-2024-092727

TY - JOUR

T1 - Effect modification and interaction between ethnicity and socioeconomic factors in severe COVID-19

T2 - analyses of linked national data for Scotland

AU - McCabe, Ronan

AU - Kibuchi, Eliud

AU - Amele, Sarah

AU - Irizar, Patricia

AU - Sheikh, Aziz

AU - Jeffrey, Karen

AU - Ruden, Igor

AU - Simpson, Colin R

AU - McCowan, Colin

AU - Ritchie, Lewis

AU - Robertson, Chris

AU - Leyland, Alastair H

AU - Demou, Evangelia

AU - Pearce, Anna

AU - Katikireddi, Srinivasa Vittal

PY - 2025/4/14

Y1 - 2025/4/14

N2 - Objective: Minority ethnic groups disproportionately experienced adverse COVID-19 outcomes, partly a consequence of disproportionate exposure to socioeconomic disadvantage and high-risk occupations. We examined whether minority ethnic groups were also disproportionately vulnerable to the consequences of socioeconomic disadvantage and high-risk occupations in Scotland. Design: We investigated effect modification and interaction between area deprivation, education and occupational risk and ethnicity (assessed as both a binary white vs non-white variable and a multi-category variable) in relation to severe COVID-19 (hospitalisation or death). We used electronic health records linked to the 2011 census and Cox proportional hazards models, adjusting for age, sex and health board. We were principally concerned with additive interactions as a measure of vulnerability, estimated as the relative excess risk due to interaction (RERI). Results: Analyses considered 3 730 837 individuals aged ≥16 years (with narrower age ranges for analyses focused on education and occupation). Severe COVID-19 risk was typically higher for minority ethnic groups and disadvantaged socioeconomic groups, but additive interactions were not consistent. For example, non-white ethnicity and highest deprivation level experienced elevated risk ((HR=2.7, 95% CI: 2.4, 3.2) compared with the white least deprived group. Additive interaction was not present (RERI=−0.1, 95% CI: −0.4, 0.2), this risk being less than the sum of risks of white ethnicity/highest deprivation level (HR=2.4, 95% CI: 2.3, 2.5) and non-white ethnicity/lowest deprivation level (1.4, 95% CI: 1.2, 1.7). Similarly, non-white ethnicity/no degree education (HR=2.5, 95% CI: 2.2, 2.7; RERI=−0.1, 95% CI: −0.4, 0.2) and non-white ethnicity/high-risk occupation (RERI=0.3, 95% CI: −0.2, 0.8) did not experience greater than additive risk. No clear evidence of effect modification was identified when using the multicategory ethnicity variable or on the multiplicative scale either. Conclusion: We found no definitive evidence that minority ethnic groups were more vulnerable to the effect of social disadvantage on the risk of severe COVID-19.

AB - Objective: Minority ethnic groups disproportionately experienced adverse COVID-19 outcomes, partly a consequence of disproportionate exposure to socioeconomic disadvantage and high-risk occupations. We examined whether minority ethnic groups were also disproportionately vulnerable to the consequences of socioeconomic disadvantage and high-risk occupations in Scotland. Design: We investigated effect modification and interaction between area deprivation, education and occupational risk and ethnicity (assessed as both a binary white vs non-white variable and a multi-category variable) in relation to severe COVID-19 (hospitalisation or death). We used electronic health records linked to the 2011 census and Cox proportional hazards models, adjusting for age, sex and health board. We were principally concerned with additive interactions as a measure of vulnerability, estimated as the relative excess risk due to interaction (RERI). Results: Analyses considered 3 730 837 individuals aged ≥16 years (with narrower age ranges for analyses focused on education and occupation). Severe COVID-19 risk was typically higher for minority ethnic groups and disadvantaged socioeconomic groups, but additive interactions were not consistent. For example, non-white ethnicity and highest deprivation level experienced elevated risk ((HR=2.7, 95% CI: 2.4, 3.2) compared with the white least deprived group. Additive interaction was not present (RERI=−0.1, 95% CI: −0.4, 0.2), this risk being less than the sum of risks of white ethnicity/highest deprivation level (HR=2.4, 95% CI: 2.3, 2.5) and non-white ethnicity/lowest deprivation level (1.4, 95% CI: 1.2, 1.7). Similarly, non-white ethnicity/no degree education (HR=2.5, 95% CI: 2.2, 2.7; RERI=−0.1, 95% CI: −0.4, 0.2) and non-white ethnicity/high-risk occupation (RERI=0.3, 95% CI: −0.2, 0.8) did not experience greater than additive risk. No clear evidence of effect modification was identified when using the multicategory ethnicity variable or on the multiplicative scale either. Conclusion: We found no definitive evidence that minority ethnic groups were more vulnerable to the effect of social disadvantage on the risk of severe COVID-19.

KW - COVID-19

KW - EPIDEMIOLOGY

KW - EPIDEMIOLOGIC STUDIES

U2 - 10.1136/bmjopen-2024-092727

DO - 10.1136/bmjopen-2024-092727

M3 - Article

SN - 2044-6055

VL - 15

JO - BMJ open

JF - BMJ open

IS - 4

M1 - e092727

ER -

Effect modification and interaction between ethnicity and socioeconomic factors in severe COVID-19: analyses of linked national data for Scotland

Abstract

Funding

Keywords

UN SDGs

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