Growth of zero-premium Medicare Advantage plans in counties with high cancer mortality.

Abstract

Zero-premium Medicare Advantage (MA) plans have rapidly become the most popular MA plan type in the US, despite potentially restrictive benefit design. It remains unclear whether the growth of these plans aligns with the county-level cancer mortality. We conducted a two-part, county-level ecological study. First, using CMS enrollment data (2019-2024) and NCHS mortality data (2018-2022), we examined longitudinal trends in the market share of zero-premium MA plans overall and across counties by their cancer-mortality rate quartiles. Second, we performed a cross-sectional, mixed-effects logistic regression analysis of 2019-2024 plan-level data to evaluate the association between zero-premium MA and low plan quality (<4 stars) and whether this relationship varied by county cancer-mortality rate quartile. The market share of zero-premium MA plans increased from 60.2% to 75.9% of the MA market between 2019 and 2024, with disproportionately greater growth in counties with higher cancer mortality rates (Q4: +28.7 percentage points[pp] vs Q1: +23.8pp; p-interaction < 0.001). In adjusted analyses, zero-premium plans also had significantly higher odds of having <4 star ratings compared with premium-charging plans (aOR 1.68; 95% CI, 1.64-1.72), particularly in counties with highest cancer mortality rates (aOR 1.83; 95% CI, 1.69-1.98, p-interaction < 0.01). The rapid expansion of zero-premium MA plans has been disproportionately concentrated in communities with highest cancer mortality rates. These plans are more likely to have lower CMS star ratings than premium-charging MA plans. Rapid zero-premium MA plan adoption raises concerns about equitable access to high-quality care for patients with cancer.