What is the prevalence and impact of multimorbidity in minority ethnic groups?

Problem

The prevalence and impact of multimorbidity in minority ethnic groups is underexplored. Here we describe the prevalence of multimorbidity and its associated mortality across ethnicities in the UK Biobank population.

Approach

A prospective study of UK Biobank: 502,643 participants aged 37-73 years; self-reported demographics, health, and lifestyle data; linked to registries to ascertain deaths. Ethnicity groups: White British, Other-White background, White Irish, Asian/Asian British, Black/Black British, Other, Mixed, or Chinese. Long-term condition (LTC) count at baseline allowed categorisation into: 0, 1, 2, 3, or ≥4 LTCs. Multimorbidity was defined as having ≥2 LTCs.Prevalence of LTC count was stratified by sex and age. Multinomial logistic regression models were used to estimate likelihood of having 0 (reference), 1, 2 , 3, or ≥4 LTCs, adjusting for demographics and lifestyle. Cox proportional hazards models were used to examine associations between LTC count and all-cause mortality (reference group: White British).

Findings

493,646 had complete data; 8,997 (1.8%) with missing data excluded. Minority ethnic groups were under-represented compared to UK population. Compared to White British they had more females, were younger, more socioeconomically deprived, smoked less, and drank alcohol less frequently. After 108.2 months (IQR 17.4) median follow up there were 19,665 (4.0%) deaths.Compared to White British, multimorbidity (stratified by sex and age) was higher in most ethnic minority groups. In those aged 56-65, the highest prevalence of ≥2 LTCs was 45.1% in Black/Black British women and 46.1% in Asian/Asian British men. Chinese generally had the lowest prevalence of multimorbidity (e.g. 24.9% Chinese women aged 56-65 had ≥2 LTCs). This pattern was similar in other age groups and at higher levels of multimorbidity.Compared to White British, adjusted ORs (95%CI) for having multimorbidity (2 vs 0 LTCs) were significantly lower for most ethnic minority groups: White-Other 0.82 (0.78-0.86); Black/Black British 0.87 (0.81-0.93); Chinese 0.63 (0.54-0.74); and Other 0.80 (0.73-0.88). However, equivalent OR for Asian/Asian British was significantly increased: 1.10 (1.04-1.17). There were lower hazard ratios for mortality for all ethnic minority groups at all levels of multimorbidity. Asian/Asian British, White-Other, and Mixed ethnicity with 2 LTCs had significantly lower mortality compared to White British: HR (95%CI) 0.73 (0.57-0.94); 0.82 (0.67-0.99); and 0.53 (0.30-0.93), respectively.

Consequences

This is the first study to examine multimorbidity and associated mortality across ethnicities in a UK population. Prevalence of multimorbidity was higher in all ethnic minority groups but, after adjusting for sociodemographics and lifestyle, the odds of having multimorbidity was lower in ethnic minority groups. Multimorbidity was associated with lower mortality in most ethnic minority groups. Caution is warranted due to under-representation of minority groups in UK Biobank. However, multimorbidity may be a key factor in explaining ethnic differences in mortality.