Estimating eligibility for GLP-1 receptor agonists for chronic weight management and cardiovascular disease in Australia

A cross-sectional analysis of the 2022 Australian National Health Survey reveals that approximately 39.7% of Australian adults (7.8 million people) are eligible for GLP-1 receptor agonist medications for chronic weight management, with a smaller subset also qualifying for secondary cardiovascular disease prevention, providing critical data for policymakers on potential access scenarios.

The Gist

Imagine Australia's population as a massive, bustling city of about 20 million adults. Now, imagine there is a new, powerful "key" (a medication called a GLP-1 receptor agonist, like Wegovy or Mounjaro) that can help people manage their weight and protect their hearts.

The big question this study asks is: "How many people in our city actually have the right 'lock' to fit this key?"

Here is the breakdown of the findings, translated from medical jargon into everyday language:

1. The Big Reveal: A Quarter of the City Fits the Key

The researchers looked at data from the 2022 National Health Survey to see who qualifies for these drugs based on the rules set by Australia's medicine regulators (the TGA).

• The Result: They found that 39.7% of all Australian adults (that's nearly 8 million people) are eligible to use these medications for chronic weight management.
• The Analogy: If you walked into a room with 10 random Australian adults, about 4 of them would technically qualify for this treatment right now.

2. How Do You Get the Key? (The Rules)

To get the key, you generally need to meet one of two criteria:

• The "Heavy" Rule: You have a Body Mass Index (BMI) of 30 or higher (clinically obese).
• The "Heavy + Trouble" Rule: You have a BMI between 27 and 30 (overweight), AND you have at least one weight-related health problem, like high blood pressure, high cholesterol, type 2 diabetes, or heart disease.

The Breakdown of the 8 Million:

• 2.9 million people qualify just because they are overweight/obese, even without other health issues.
• 3.3 million people qualify because they are overweight plus have one other health issue.
• 1.7 million people qualify because they are overweight plus have two or more health issues.

3. The Heart Protection Bonus

There is a second, more specific "key" for people who already have heart disease.

• About 339,000 Australians (roughly 3.7% to 4.3% of the total population) qualify for the drug specifically to prevent a second heart attack or stroke.
• The Catch: These people must have established heart disease and be overweight (BMI ≥27), but they cannot have diabetes (since they already have a different drug for that).

4. The "Who Pays?" Problem

Here is where the story gets tricky. Just because you qualify for the key doesn't mean you can afford it.

• The Cost: Currently, these drugs are not subsidized by the government (PBS) for weight loss or heart protection. If you buy them privately, it costs about $5,200 AUD per year.
• The Math: If the government decided to pay for everyone who qualifies (all 8 million people), it would cost roughly $40 billion a year.
• The Reality Check: That is more than the entire estimated economic cost of obesity in Australia for a whole year! It's a massive bill that the government would need to think very carefully about.

5. The Inequality Gap

The study found that the "lock" isn't distributed evenly.

• People in low-income households are actually more likely to qualify (44.4%) than those in wealthy households (36.7%).
• The Analogy: The people who need the key the most (those with lower incomes and more health struggles) are the ones who can least afford to buy it without help. This creates a fairness issue.

6. The Policy Puzzle

The authors suggest that the government might need to play "Tetris" with the rules to make this affordable:

• Option A: Only pay for people with a BMI over 35 (the "very heavy" group). This would cut the number of eligible people down to about 2.5 million.
• Option B: Only pay for people with a BMI over 35 and at least one other health problem. This cuts it down further to about 1.5 million.

The Dilemma: While this saves money, the study warns that these drugs work well for people with lower BMIs (27–35) too. By setting the bar too high, we might be locking out people who could still benefit significantly.

The Bottom Line

This study is like a population census for a new medical tool. It tells us that:

1. Huge numbers of Australians are eligible for these life-changing drugs.
2. Money is the main barrier. Without government subsidies, most people can't afford them.
3. Fairness is at risk. The people who need them most are often the poorest.
4. Decision time: Policymakers now have the numbers they need to decide how to balance the budget with the health of the nation. They have to decide: Do we open the door to everyone, or do we build a smaller, more expensive gate?

Note: This is a preprint, meaning it is a draft study that hasn't been fully peer-reviewed yet, but it provides a very clear snapshot of the current situation in Australia.

Technical Summary

1. Problem Statement

Glucagon-like peptide-1 receptor agonists (GLP-1RAs) have received regulatory approval in Australia by the Therapeutic Goods Administration (TGA) for three primary indications: Type 2 diabetes, chronic weight management, and secondary prevention of cardiovascular disease (CVD). While currently subsidized for Type 2 diabetes under the Pharmaceutical Benefits Scheme (PBS), there is no current subsidy for obesity or CVD prevention.

Despite recent recommendations by the Pharmaceutical Benefits Advisory Committee (PBAC) to consider subsidizing semaglutide for CVD prevention, the total population-level eligibility for these expanded indications remains unknown. Policymakers lack reliable, nationally representative data to:

• Estimate the potential volume of patients eligible for treatment.
• Understand the economic implications of broad subsidies (estimated at ~$AUD 40.7 billion annually at current private prices).
• Assess equity issues, as high out-of-pocket costs may create barriers for lower-income populations.

2. Methodology

Data Source:
The study utilized a cross-sectional analysis of the 2022 National Health Survey (NHS) conducted by the Australian Bureau of Statistics (ABS).

• Sample: 13,039 non-pregnant adults aged ≥18 years residing in private dwellings.
• Weighting: Person-level survey weights were applied to generate nationally representative estimates for the ~19.7 million adult population. Jackknife replicate weights were used to calculate 95% confidence intervals (CIs).

Eligibility Criteria (TGA Approved Indications):
The authors defined eligibility based on current TGA approvals for semaglutide and tirzepatide:

1. Chronic Weight Management:
   • BMI ≥30 kg/m² (Obesity), OR
   • BMI ≥27 kg/m² to <30 kg/m² (Overweight) AND at least one weight-related comorbidity.
   • Comorbidities included: Hypertension, dyslipidaemia, cardiovascular disease (CVD), or Type 2 diabetes. (Obstructive sleep apnoea was excluded due to lack of survey data).
2. Secondary Prevention of CVD:
   • Established CVD (prior myocardial infarction, prior stroke, or symptomatic peripheral arterial disease) AND
   • BMI ≥27 kg/m² AND
   • Absence of Type 2 diabetes.
   • Definitions: "Confirmed" CVD was limited to MI or stroke (directly recorded). "Possible" CVD included broader vascular diseases (ICD-10 I70-I79) to provide an upper-bound estimate.

Statistical Analysis:
Analyses were performed using Stata V.18.0. The study estimated the total number and proportion of eligible adults across subgroups defined by age, sex, socioeconomic status (income quintiles, education), and clinical history.

3. Key Contributions

• First National Estimates: This is the first study to provide nationally representative estimates of GLP-1RA eligibility in Australia for weight management and CVD prevention.
• Granular Subgroup Analysis: The study breaks down eligibility by BMI categories, comorbidity counts, and socioeconomic factors, offering a nuanced view of the affected population.
• Policy-Relevant Scenarios: It models eligibility under various hypothetical coverage scenarios (e.g., restricting subsidies to BMI >35 kg/m² or requiring specific comorbidities) to assist in cost-containment planning.
• Equity Assessment: It highlights the disparity in eligibility across income groups, noting that lower-income populations have higher eligibility rates but face greater financial barriers to access.

4. Key Results

Overall Eligibility for Chronic Weight Management:

• Total Eligible: 39.7% of Australian adults (approx. 7.8 million individuals; 95% CI 7.6–8.1 million).
• Comorbidity Breakdown:
  • 2.9 million had no weight-related comorbidities (BMI ≥30).
  • 3.3 million had ≥1 comorbidity.
  • 1.7 million had ≥2 comorbidities.
• Socioeconomic Disparity: Eligibility was highest in the lowest income quintile (44.4%) compared to the highest income quintile (36.7%).
• Clinical History: High eligibility rates were observed among those with Type 2 diabetes (70.3%), hypertension (65.6%), and dyslipidaemia (64.8%).

Eligibility for Secondary Prevention of CVD:

• Total Eligible: Up to 338,900 adults (95% CI 271.3k – 406.5k).
  • Confirmed CVD (MI/Stroke): ~285,700 adults.
  • Possible CVD (Broader vascular disease): ~53,200 additional adults.
• Intersection: Among the 7.8 million eligible for weight management, only ~4.3% (338.9k) also met the criteria for CVD prevention.

Coverage Scenario Modeling:

• Limiting subsidies to BMI >35 kg/m² would reduce the eligible pool to ~2.5 million adults.
• Further restricting to BMI >35 kg/m² + ≥1 comorbidity would reduce the pool to ~1.5 million adults.
• For CVD prevention, limiting to BMI >35 kg/m² would reduce the eligible pool to ~88,100 adults.

5. Significance and Implications

• Economic Impact: The study underscores the massive fiscal challenge of universal coverage. At current private prices (~$5,200 AUD/year), covering all 7.8 million eligible adults would cost ~$40.7 billion annually, exceeding the estimated $38 billion annual economic burden of obesity itself.
• Clinical Efficacy vs. Cost Containment: The authors note that while restricting access based on BMI (e.g., >35 kg/m²) reduces costs, post-hoc analyses of major trials (STEP, SURMOUNT, SELECT) suggest efficacy across all BMI groups >27 kg/m². Restricting access based on BMI may deny treatment to patients who would clinically benefit.
• Health Equity: The finding that nearly 45% of low-income households are eligible highlights a critical access barrier. Without subsidies, these populations are unlikely to afford treatment, exacerbating health inequities.
• Policy Guidance: The data provides a baseline for the PBAC and government to design subsidy schemes that balance fiscal sustainability with clinical need and equity. It suggests that a "one-size-fits-all" subsidy is financially unviable, necessitating tiered approaches based on risk profiles (BMI + comorbidities).

Limitations:

• Exclusion of obstructive sleep apnoea (a key comorbidity) likely leads to a conservative underestimation of eligibility for the BMI 27–29.9 group.
• Inability to specifically identify symptomatic peripheral arterial disease in the survey data.
• Reliance on self-reported/imputed height and weight for BMI calculation.

Conclusion:
Approximately 7.8 million Australian adults are eligible for GLP-1RAs for weight management, with a smaller subset eligible for CVD prevention. The study serves as a critical reference for policymakers to navigate the tension between the high clinical need, the potential for significant health benefits, and the substantial economic constraints of subsidizing these medications.