Covariate Ascertainment

Self‐identified race was categorized as white, black, Asian/Pacific Islander, and other. Due to the small number of nonwhite participants, race was dichotomized as white versus nonwhite for the regression analyses. Self‐identified sex was classified as male or female. Level of education was determined according to self‐reported number of educational years. Anthropometric measurements included weight, height, and waist and hip circumferences. Blood pressure and heart rate were measured in the right arm of seated participants after a 5‐minute rest period using an appropriately sized cuff, and the average of 2 measurements was used for analysis.

Hypertension was defined as either a reported history of physician‐diagnosed hypertension combined with the use of antihypertensive medications or a baseline study visit systolic blood pressure ≥140 mm Hg or diastolic pressure ≥90 mm Hg. Diabetes mellitus was defined as use of an antihyperglycemic medication at baseline or a fasting glucose level ≥126 mg/dL. Congestive heart failure and myocardial infarction (MI) were identified by participant self‐report and confirmed by medical record verification.9 Coronary heart disease was defined as angina, previous MI, previous coronary artery bypass graft surgery, or previous angioplasty identified by participant self‐report and confirmed by medical record verification.9 Atrial fibrillation was defined as a reported history of atrial fibrillation at the first study encounter, on baseline 12‐lead ECG, or on baseline Holter monitoring.

Usual leisure‐time activity was assessed using a modified, validated Minnesota Leisure‐Time activity questionnaire.10 The questionnaire evaluated frequency and duration of 15 different activities during the preceding 2 weeks, including gardening, mowing, raking, swimming, hiking, aerobics, tennis, jogging, racquetball, walking, golfing, bicycling, dancing, calisthenics, and exercise cycling. Each activity was defined as having an intensity value in metabolic equivalent task units, and participant responses regarding types, frequency, and duration of each activity were used to calculate weekly energy expenditure (kcal/week) from leisure‐time activity. Usual exercise intensity was also separately assessed: based on the highest‐intensity leisure‐time activity reported over the preceding 2 weeks, participants were categorized as having engaged in high, moderate, or low‐intensity activity or none, where high‐intensity activity was estimated to require >6 metabolic equivalent tasks.10 To ascertain the association of at least moderately intensive exercise with PVC frequency, exercise intensity was dichotomized into no and low‐intensity exercisers versus moderate‐ and high‐intensity exercisers for regression analyses.

Baseline angiotensin‐converting enzyme inhibitor, β‐blocker, and calcium channel blocker use were ascertained using an in‐home medication inventory. Use of a particular medicine required a current prescription filled by a pharmacist or physician that was taken by the patient in the previous 2 weeks.11

Self‐reported usual consumption of the number of alcoholic drinks (1 drink was defined as a 12‐ounce can or bottle of beer, a 6‐ounce glass of wine, or a shot of liquor) was used to estimate weekly alcohol consumption. Smoking status was dichotomized as ever (current and former) versus never and was quantified as the average daily consumption of cigarettes when smoking, the length of smoking history in years, and average packs of cigarettes per day based on self‐report. Smoking pack‐years were calculated by multiplying the average packs of cigarettes per day by the duration of smoking in years.8

The echocardiographic assessment of participants in the CHS has been previously described.12 In brief, 2‐dimensional echocardiography, 2‐dimensional targeted M‐mode, and Doppler imaging were performed on each participant at baseline using Toshiba SSH‐160A echocardiography machines (Toshiba Medical Systems, Tustin, CA) equipped with 2.5‐ and 3.75‐MHz transducers. Imaging was performed at the highest Mhz that provided adequate tissue penetration for 2‐dimensional imaging. Images were recorded and stored on Super‐VHS videotape at the recruitment sites and then transferred to the University of California, Irvine, for central interpretation.12 In all participants, left ventricular (LV) function was qualitatively assessed from the 2‐dimensional imaging views, where at least 80% of the myocardium was visualized. Function was categorized qualitatively as normal, borderline, or abnormal, with 94% interreader agreement and 98% intrareader agreement of paired studies.12 Because of the small number of participants with ejection fraction classified as “abnormal,” qualitative ejection fraction was dichotomized for regression analyses into (1) borderline or abnormal versus (2) normal. In a subpopulation of 952 individuals, LV mass and fractional shortening were derived from M‐mode measurements, using leading‐edge‐to‐leading‐edge methodologies per American Society of Echocardiography standards.13 LV mass was calculated using the Devereux formula and indexed by dividing it by the body surface area.14