Table 2.

Hazard Ratio (HR) and 95% Confidence Interval (CI) of Atrial Fibrillation by Serum Magnesium Quintile, Atherosclerosis Risk in Communities, 1987 to 2009

	Serum Magnesium (mEq/L)					P for Trend*
	<1.55 (n=3118)	1.55–1.60 (n=2620)	≥1.60–1.65 (n=3100)	≥1.65–1.75 (n=2739)	≥1.75 (n=2713)
Cases	466	297	351	313	328
Person-years	53,896	49,347	57,131	50,218	50,427
Crude Incidence Rate (per 1000 person-years)	8.65	6.02	6.14	6.23	6.50
Model 1 HR (95% CI)	1.60 (1.39–1.84)	1.02 (0.87–1.19)	1.00 (Reference)	0.99 (0.85–1.15)	1.00 (0.86–1.17)	<0.0001
Model 2 HR (95% CI)	1.34 (1.16–1.54)	1.00 (0.85–1.16)	1.00 (Reference)	1.04 (0.89–1.21)	1.05 (0.90–1.22)	0.005
Model 3 HR (95% CI)	1.34 (1.16–1.54)	0.99 (0.85–1.16)	1.00 (Reference)	1.04 (0.90–1.22)	1.06 (0.91–1.23)	0.008
Model 4 HR (95% CI)	1.24 (1.08–1.43)	1.00 (0.85–1.16)	1.00 (Reference)	1.10 (0.94–1.28)	1.10 (0.94–1.28)	0.26

Model 1: Cox proportional hazards model adjusted for age, sex, race, and study site.

Model 2: Model 1 with additional adjustment for body mass index, high density lipoprotein cholesterol, low density lipoprotein cholesterol, serum potassium, serum creatinine, smoking status, drinking status, educational level, systolic blood pressure, diabetes, and antihypertensive medication.

Model 3: Model 2 with additional adjustment for prevalent myocardial infarction, heart failure, or stroke at baseline.

Model 4: Model 3 with additional adjustment for incident myocardial infarction, heart failure, or stroke as time-varying covariates.

^*Linear trend in quintile number.