Table 1.

Baseline Characteristics of the 7828 Study Participants

Characteristic	Patients, %a
Age, mean (SD), y	56.5 (12.4)
Male sex	45.1
Race
Non-Hispanic white	80.6
Non-Hispanic black	9.0
Mexican American	3.6
High school education	70.7
Annual household income <$20 000	31.1
Systolic blood pressure, mean (SD), mm Hg	128.7 (18.2)
Total cholesterol level, mean (SD), mg/dL	218.0 (42.1)
HDL cholesterol level, mean (SD), mg/dL	51.0 (16.1)
BMI, mean (SD)	27.3 (5.5)
Serum potassium level, mean (SD), mEq/L	4.1 (0.3)
Serum calcium level, mean (SD), mg/dL	9.2 (0.4)
Diabetes mellitus	8.6
Myocardial infarction	5.2
Congestive heart failure	2.9
Smoking status
Current	22.9
Former	34.7
Never	42.4
Consume alcohol	45.8
Use QT-prolonging medication	12.0
Use a β-blocker	7.9
Heart rate, mean (SD), beat/min	68.1 (11.5)
QT interval, mean (SD), ms	406.1 (30.8)
QTrras, mean (SD), ms	406.1 (18.8)
QTb, mean (SD), ms	429.3 (23.3)

Abbreviations: BMI, body mass index (calculated as weight in kilograms divided by height in meters squared); HDL, high-density lipoprotein; QTb, Bazett heart rate–corrected QT interval; QTrras, age-, race-, sex-, and R-R interval–adjusted QT interval.

SI conversion factors: To convert calcium to millimoles per liter, multiply by 0.25; cholesterol to millimoles per liter, multiply by 0.0555; and potassium to millimoles per liter, multiply by 1.

^aData are expressed as percentage of patients unless otherwise indicated.