A recent study published in PLoS ONE explored all-cause mortality risk among individuals with type 2 diabetes (T2D) from different ethnic backgrounds. By conducting a systematic review and meta-analysis, researchers from the United Kingdom assessed mortality trends across a range of ethnic groups, providing new insights into the varying risks of mortality for people with T2D based on ethnicity.
Background
T2D has become a global health challenge, contributing to nearly double the mortality risk compared to individuals without diabetes. The primary causes of death among those with T2D include circulatory diseases, cancer, and neurodegenerative conditions. Though advances in diabetes management have reduced vascular-related deaths, ethnic disparities in diabetes-related outcomes remain an underexplored area of research.
Ethnic groups, particularly South Asian and Black populations, experience higher prevalence rates, earlier onset, and different complication profiles compared to White populations. Despite the importance of ethnicity in T2D outcomes, the varying mortality risks across ethnic groups have not been comprehensively examined, with broader ethnic categories often masking crucial subgroup differences. This study aims to bridge that gap by investigating how ethnicity influences T2D mortality risk.
About the Study
The systematic review adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and was registered with the Prospective Register of Systematic Reviews (PROSPERO). A comprehensive search strategy was employed across nine databases, including Ovid Medline, Embase, PsycInfo, and Global Health, with updates in May 2024. The criteria for inclusion were strict: only longitudinal cohort studies comparing at least two ethnic groups were considered.
Eligible studies involved adults aged 18 years or older with T2D. The analysis included studies that provided hazard ratios (HRs) for all-cause mortality and excluded studies that were not based on population cohorts, such as cross-sectional studies. Quality assessments were conducted using the Newcastle-Ottawa Scale (NOS), with a preference for studies with minimal adjustment to avoid confounding variables.
Study Results
The research revealed striking ethnic differences in diabetes-related mortality. Notably, South Asians, particularly Bangladeshis, showed a notable survival advantage. While the South Asian group as a whole experienced a 32% lower mortality risk, Bangladeshi individuals had a 37% reduction (HR 0.63, 95% CI 0.46–0.86). In contrast, Pakistani and Indian groups showed trends toward lower mortality risk, although these findings were not statistically significant.
In Singapore, the findings were particularly eye-opening, as Malay individuals faced a significant 42% higher mortality risk than their Chinese counterparts. Indian individuals had a non-significant 26% increase in mortality risk, challenging the assumption that White populations universally exhibit the highest mortality risks for diabetes-related deaths.
The meta-analysis included 13 studies with over 573,000 participants and spanned countries like the USA, UK, New Zealand, Australia, Canada, and Singapore. These studies consistently found that South Asian, Black, and Chinese ethnic groups experienced significantly lower mortality risks than White populations. The HRs were 0.68 (95% CI 0.65-0.72) for South Asians, 0.82 (95% CI 0.77-0.87) for Black populations, and 0.57 (95% CI 0.46-0.70) for Chinese individuals. However, the findings for Chinese ethnicity showed high heterogeneity (I² = 90%), indicating that variability in study populations or methodologies may have influenced results.
Additional findings from narrative synthesis revealed that Indigenous populations, such as Māori in New Zealand and Indigenous Australians, had higher mortality risks compared to their European or Anglo-Celtic counterparts. Conversely, Mediterranean and Arabic populations in Australia had lower mortality risks than Anglo-Celtic groups. Studies from the USA and UK also highlighted varying mortality risks among Hispanic, Asian, African, and Caribbean ethnic groups, showcasing nuanced ethnic disparities.
Conclusions
The study found that individuals with T2D from South Asian, Black, and Chinese ethnicities experienced significantly lower all-cause mortality risks compared to White populations, with reductions of 32%, 18%, and 43%, respectively. However, Indigenous populations, such as Māori and Indigenous Australians, faced higher mortality risks. The findings underscore the complexity of ethnicity-related mortality differences and the need for further research to identify the factors that drive these disparities.
The authors emphasize the limitations of their research, including the reliance on broad ethnic categories that might obscure subgroup differences, as well as the potential for over-adjustment in statistical models across studies. Future studies should focus on refining ethnic categorization and exploring causal factors to better inform targeted interventions for improving outcomes in T2D management across diverse populations.
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