Global research discovers different diabetes mortality risks by ethnicity

Global research discovers different diabetes mortality risks by ethnicity

A systematic review of 573,173 people with type 2 diabetes found that South Asian, black and Chinese ethnic groups have significantly lower all-cause mortality risks compared to white populations, while Māori and Indigenous Australians face higher mortality.

In a study recently published in the journalPLOS oneResearchers in the United Kingdom compared the risk of all-cause mortality in people with type 2 diabetes (T2D) across ethnic groups through a systematic review and meta-analysis.

background

Bangladeshi patients show the strongest survival benefit. While South Asians overall had lower mortality of 32%, Bangladeshi individuals stood out with a striking reduction of 37% (HR 0.63, 95% CI 0.46–0.86), while Pakistani and Indian subgroups showed lower risk trends, but their differences were not statistically significant.

T2D is a major global health problem that nearly doubles the risk of mortality compared to those without diabetes, primarily due to circulatory diseases but increasingly cancer and neurodegenerative diseases.

Ethnicity is a significant risk factor, with South Asian and black populations having higher prevalence, earlier onset, and different complication profiles compared to white populations. While advances in T2D management have reduced vascular mortality, ethnic differences in outcomes remain under investigation, and broad ethnic categories used in studies may mask important subgroup differences.

Further research is needed to examine factors driving these disparities and guide targeted interventions to improve outcomes in T2D management in diverse populations.

About the study

The present systematic review was conducted according to the preferred reporting positions for systematic reviews and meta-analyses (PRISMA) guidelines. The protocol was registered in the international prospective registry of systematic reviews (Prospero). Articles were searched in nine databases including Ovid Medline, Embase, Psycinfo, Global Health and others in March 2023, with updates in May 2024.

The search strategy used a combination of controlled vocabulary (medical subject headings [MeSH]) and keyword searching using Boolean operators. Searches were completed by group consensus for terms related to T2D, ethnicity, and longitudinal cohort studies, excluding studies with data collection or follow-up before 2000.

Eligible studies included adults aged 18 years or older with T2D from population-based settings. Studies had to compare at least two ethnic groups without restrictions on location, language or health status. Exclusion criteria focused on studies of children, type 1 diabetes, gestational diabetes, or populations selected for specific comorbidities. Longitudinal cohort studies and secondary analyzes of randomized controlled trials (RCTs) were included, while other designs such as case series or cross-sectional studies were excluded.

Study quality was assessed using the Newcastle-Ottawa Scale (NOS), and data analysis included meta-analysis for studies reporting hazard ratios (HRS) for all-cause mortality. Statistical heterogeneity was assessed using the I² statistic and forest plots were generated using Revman 5.4. Narrative synthesis was performed for studies with outcomes not reported as HRS. Minimum adjustment models (age and sex) were preferred for meta-analysis to avoid concordance, although some studies used maximum adjustment models that could obscure causal relationships.

Study results

Singapore is flipping the script on risk hierarchies. In the Singapore cohort, Malaysian individuals faced a significant 42% higher risk of mortality than their Chinese counterparts, while Indian individuals showed a non-significant risk of 26%, challenging the assumption that white populations universally have the highest diabetes mortality risks.

An initial search in March 2023, updated in May 2024, yielded 33,922 studies from nine databases with an additional 3,097 studies in the update. After removing duplicates, 16,520 studies underwent title and abstract screening, resulting in 292 full-text articles for further review. Ultimately, 13 studies met the inclusion criteria for this analysis and focused on mortality outcomes in T2D. Of these, seven studies provided sufficient data for meta-analysis, while six were included in a narrative synthesis.

The 13 studies published between 2010 and 2021 included 573,173 participants with T2D and were conducted in different countries: four in the United States of America (USA), three in the United Kingdom (UK), two each in New Zealand and Australia. and one each in Canada and Singapore.

Most studies compared ethnic groups to white ethnicity, except for one study that used Chinese ethnicity as the reference group. The follow-up duration ranged from 4 to 18 years. Using the NOS, 12 studies were rated “good” for methodological quality, while one was rated “poor” due to inadequate follow-up. However, the different study designs and population characteristics may impact generalizability, particularly outside North America, the United Kingdom and Australasia.

The meta-analysis revealed significant insights into the risk of all-cause mortality. Four studies comparing South Asian ethnicity with white ethnicity reported a lower risk of mortality for South Asians with a hazard ratio (HR) of 0.68 (95% CI 0.65-0.72). Similarly, five studies examining black ethnicity showed a reduced risk of mortality compared to white ethnicity, HR 0.82 (95% CI 0.77-0.87). In Chinese ethnicity, two studies showed a lower risk of mortality compared to white ethnicity, HR 0.57 (95% CI 0.46-0.70), but with high heterogeneity (I² = 90%), indicating variability in study populations or methods.

The narrative synthesis highlighted additional findings. Indigenous populations, including Māori in New Zealand and Indigenous Australians, faced higher mortality risks compared to European or Anglo-Celtic groups. The Mediterranean and Arab ethnic groups in Australia showed lower mortality risks compared to Anglo-Celtic populations. Studies from the United States and United Kingdom reported differential mortality risks among Hispanic, Asian, African, and Caribbean ethnic groups, reflecting nuanced patterns of ethnic differences.

A study from Singapore used a non-white reference group that showed higher mortality risks in Malay and Indian ethnicities compared to Chinese ethnicity. These findings highlight the complexity of ethnic mortality disparities and the need for further research to uncover underlying factors.

Conclusions

In summary, this study found that individuals with T2D from South Asian, Black, and Chinese ethnicities have significantly lower all-cause mortality risks compared to White ethnicity, with 32%, 18%, and 18%, respectively. 43% were reduced. Conversely, Indigenous populations such as Māori New Zealanders and Indigenous Australians face higher mortality risks. The review, which included 13 studies and over 500,000 participants, showed consistent results across different settings. However, the authors note limitations, including reliance on broad ethnic categories, which can detect subgroup differences and possible concordance in statistical models due to variable selection across the study via which variable confounding factors.

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