Table 1.

Participant characteristics by QT interval corrected for heart rate duration at each person visit (N=16,451)

Characteristics	All	QTc<450 ms	QTc≥450 ms
N visits (%)	16,451	15,694 (95.4)	757 (4.6)
Age, yr	60±11	60±11a	62±9
Men, %	53	54a	40
Race/ethnicity, %
Non-Hispanic white	46	47a	34
Non-Hispanic black	40	40a	52
Hispanic	9	9b	7
Other race/ethnicity	4	4a	7
Self-reported comorbidity, %
MI/revascularization	23	22a	36
Congestive heart failure	8	7a	20
Diabetes	47	47a	56
Hypertension	90	89a	95
Stroke	10	10a	17
Current smoker, %	11	11a	15
Body mass index, kg/m2	31.9±7.8	31.8±7.7a	33.9±8.4
eGFR, ml/min per 1.73 m2	42±15	42.6±15.1a	37±16
Serum potassium, mmol/l	4.4±0.5	4.4±0.5a	4.1±0.6
Serum calcium, mg/dl	9.3±0.5	9.3±0.5	9.1±0.7
Serum magnesium, mg/dl	2.0±0.3	2.0±0.3c	2.0±0.3
Systolic BP, mm Hg	127±21	126±21a	135±27
Diastolic BP, mm Hg	70±13	70±12	70±15
Heart rate, min−1	65±11	65±11a	63±10
QTc duration, ms	414±21	413±17d	462±16

Values expressed as mean±SD. Footnotes refer to comparisons according to QTc group. QTc, QT interval corrected for heart rate; MI, myocardial infarction.

^aP<0.001.

^bP<0.05.

^cSerum magnesium available only at baseline visit (n=3252 visits).

^dP value irrelevant (grouping variable).