Background: Cardiotoxic treatments and lifestyle changes after cancer diagnosis may alter the impact of risk factors for hypertension, such as central or overall obesity, in survivor populations.

Methods: We assessed obesity in relation to hypertension risk among 1,151 women ages 35-74 years who enrolled in the Sister Study in 2003-2009 with a history of prior cancer (excluding breast cancer). Blood pressure, weight, height, and waist and hip circumference were examiner-measured at enrollment. Eligible participants were hypertension-free (systolic/diastolic blood pressure <140/90 mmHg, no prior hypertension diagnosis or antihypertensive medication use) at enrollment. Incident hypertension was defined as self-reported physician diagnosis or antihypertensive medication use through Sept 2021. Obesity was defined by body mass index (BMI)≥30 kg/m2 or waist-hip ratio (WHR)≥0.85, in four phenotypes (none, WHR-only, BMI-only, and both WHR/BMI obesity). Multivariable Cox regression models were used to estimate hazard ratios (HR) and 95% confidence intervals (CI) for hypertension risk.

Results: Among 1,151 female survivors, 14.5% met thresholds for obesity by WHR only, 11.6% by BMI only, and 9.4% by both. Over follow-up (median=11.6 years), 400 women (34.8%) developed hypertension. Compared with no obesity, obesity by BMI (HR 1.66, 95% CI 1.20-2.29) and both WHR/BMI (HR 1.63, 95% CI 1.18-2.26) was associated with increased risk of hypertension; WHR-only associations were not statistically significant (HR 1.24, 95% CI 0.92-1.67). There was no evidence of multiplicative interaction. BMI-based “overweight” (≥25 kg/m²) was also positively associated with hypertension risk (BMI-only: HR 1.29, 95% CI 1.01-1.63; WHR/BMI: HR 1.52, 95% CI 1.14-2.01). Associations did not depend on time since cancer diagnosis.

Conclusion: Obesity defined by BMI alone or combined with WHR (as a measure of central obesity) was positively associated with hypertension incidence in female cancer survivors.