Introduction
Little is known about the potential role of diuretics as modifiers of the relationship between ambient ultraviolet radiation (UVR) and risk of keratinocyte carcinomas (KC) including basal (BCC) and squamous cell carcinomas (SCC).
Methods
We included U.S. Medicare beneficiaries with diagnosis of hypertension at baseline, were aged 66–<85 and non–Hispanic white (N=6,539,996). We followed patients from 1/1/2012, to the earliest events: KC diagnosis, death, lost coverage of Part A/B/non–Health Maintenance Organization (HMO), switching to HMO, turning 85-years-old, or 12/31/2018. Satellite–based ambient UVR was linked to patients’ zip codes at baseline. Time–dependent duration of diuretic use was based on Part D prescription claims. KCs were ascertained using administrative diagnoses and procedure codes.
Results
There were 1,393,883 KCs during over 30 million person–years of follow-up. BCC and SCC incidence rates per year usage increased by 0.8% (95% confidence interval [CI]: 0.7%,0.9%) and 2.4% (2.3%,2.5%) for hydrochlorothiazide, and 0.9% (0.7%,1.0%) and 4.1% (3.9%,4.3%) for furosemide, and 1.0% (0.8%,1.2%) and 4.1% (3.9%,4.3%) for triamterene. However, SCC rate reduced by 1.0% (95% CI: 0.5%,1.4%) per year of chlorthalidone use. Increased KCs rates remained for most diuretics in patients with low and high UVR.
Conclusions
Patients with claims of hydrochlorothiazide, furosemide or triamterene had increased KCs rate, independent of UVR. However, patients with chlorthalidone claims did not have increased SCC rate. Considerations in interpreting the diuretic-KCs associations include lack of information before age 65 about diuretic use, prior history of KCs, and potential misclassification of individual UVR using the proxy of ambient exposure.