Multivariate model of GEE for the likelihood of undergoing valve surgery.

GEE, generalized estimating equation; Municipality-level mean income represents mean household income adjusted for regional price index. 1st 2nd, 3rd, and 4th quartiles of income: ≤2,799.5, 2,799.6–3,253.2, 3,253.3–3,719.1, ≥3,719.2 (1,000 yen); Hospital volume: the number of aortic valve surgery procedures performed during 2011 at each institution. AS, aortic stenosis; BMI, body mass index; CI, confidence interval; NYHA: New York Heart Association; NA, not available; OR, odds ratio. Multivariate model of GEE for the likelihood of undergoing valve surgery.