Adjusted difference (95%CI) in QT interval duration by categories of smoking, pack-years, and serum cotinine.

a. Adjusted for age (continuous), race-ethnicity (non-Hispanic white, non-Hispanic black, Mexican-American, other), sex, and RR-interval (restricted quadratic splines with knots at the 5th, 50th, and 95th percentiles).
b. Further adjusted for BMI (continuous), high school education (yes, no), annual household income (<$20,000, ≥$20,000), and use of QT-prolonging medications (yes, no).
c. Further adjusted for systolic blood pressure, blood pressure lowering medication, total and HDL cholesterol, diabetes, history of myocardial infarction, history of congestive heart failure, serum potassium (continuous), and serum calcium (continuous).
d. Further adjusted for coffee (continuous), tea (continuous), number of drinks (continuous), and total physical activity (continuous).