The Underrepresentation of Black and Hispanic Persons Among Study Participants
The underrepresentation of Black and Hispanic persons among study participants is a significant limitation of the SURMOUNT-5 trial, as this restricts the generalizability of the findings to these populations who are disproportionately affected by obesity and its cardiovascular complications.
Why This Matters
The SURMOUNT-5 trial compared tirzepatide with semaglutide in adults with obesity but without type 2 diabetes 1. While the trial demonstrated superior weight reduction with tirzepatide, the lack of racial and ethnic diversity in the study population creates uncertainty about whether these results apply equally to Black and Hispanic populations.
Evidence from Similar Trials
Multiple high-quality guidelines and trials have explicitly identified underrepresentation of racial and ethnic minorities as a critical limitation:
In lupus nephritis trials (BLISS-LN), the cohort was predominantly Asian with underrepresentation of Black and Hispanic participants, which was specifically noted as limiting the applicability of findings to these populations 2
In breast cancer radiation trials, the relatively small number of Black, Hispanic, or Asian patients enrolled limited understanding of potential differences in these populations. Prior studies demonstrated that Asian, Black, and Hispanic patients experience worse acute and long-term outcomes, yet their lack of representation should not limit their access to treatments 3
In cardiovascular risk assessment guidelines, the race-specific Pooled Cohort Equations were developed specifically for non-Hispanic African Americans and non-Hispanic Whites, with only expert opinion supporting use in other populations 4
Why the Other Options Are Not Primary Limitations
Open-Label Study Design
While open-label designs can introduce bias, this is not a major limitation for SURMOUNT-5 because:
- Weight reduction (the primary endpoint) is an objective, measurable outcome
- Cardiometabolic parameters are laboratory-based and not subject to observer bias
- The comparison between two active treatments (rather than placebo) reduces the impact of expectation bias
Exclusion of Patients with Diabetes
This is not a limitation but rather the intended study design. SURMOUNT-5 specifically aimed to evaluate these medications in people with obesity without diabetes 1. Separate trials exist for populations with diabetes, making this an appropriate inclusion criterion rather than a flaw.
Assumption About Surgical Weight-Reduction Procedures
This is not mentioned as a design element in the SURMOUNT-5 trial evidence provided. The trial focused on pharmacologic weight management, and there is no indication that prior surgical procedures were assumed to represent ineffective drug treatment.
Clinical Implications
The underrepresentation of Black and Hispanic persons is particularly problematic because:
- Higher disease burden: These populations have higher rates of obesity and obesity-related cardiovascular disease
- Potential biological differences: Different populations may have varying responses to GLP-1 receptor agonists
- Healthcare disparities: These groups already face barriers to accessing obesity treatments 3
When prescribing tirzepatide or semaglutide to Black and Hispanic patients, clinicians should recognize that the magnitude of benefit demonstrated in SURMOUNT-5 may not fully represent the response in these populations, though there is no evidence suggesting reduced efficacy. Close monitoring and individualized assessment remain essential until more diverse trial data become available.