Table 2. Hazard ratio (HR) and 95% confidence interval (CI) of atrial fibrillation (AF) by total white blood cell (WBC) count, Atherosclerosis Risk in Communities Study, 1987 to 2010.
| Total WBC Count (x 109/L) | ||||||
|---|---|---|---|---|---|---|
| 3.0–4.6 | 4.7–5.4 | 5.5–6.2 | 6.3–7.4 | 7.5–12.0 | Linear | |
| (n = 2970) | (n = 2966) | (n = 2769) | (n = 3002) | (n = 2793) | (per 1-SD* Increase) | |
| AF Cases | 300 | 326 | 377 | 453 | 472 | 1928 |
| Person-years | 58,663 | 57,492 | 52,712 | 54,358 | 48,137 | 271,362 |
| Crude Incidence Rate (per 1000 person-years) | 5.1 | 5.7 | 7.2 | 8.3 | 9.8 | 7.1 |
| Model 1 HR | 1 | 1.08 | 1.33 | 1.59 | 1.97 | 1.28 |
| (95% CI) | (Reference) | (0.92–1.26) | (1.14–1.55) | (1.37–1.84) | (1.70–2.28) | (1.23–1.34) |
| Model 2 HR | 1 | 0.99 | 1.08 | 1.16 | 1.23 | 1.09 |
| (95% CI) | (Reference) | (0.84–1.16) | (0.93–1.26) | (1.00–1.36) | (1.05–1.44) | (1.04–1.15) |
| Model 3 HR | 1 | 0.99 | 1.03 | 1.05 | 1.07 | 1.03 |
| (95% CI) | (Reference) | (0.84–1.16) | (0.88–1.20) | (0.90–1.23) | (0.91–1.26) | (0.98–1.08) |
Model 1: Cox proportional hazards model adjusted for age, race, sex, and study site.
Model 2: Model 1 with additional adjustment for body mass index, chronic obstructive pulmonary disease, diabetes mellitus, drinking status, educational level, height, pack-years, smoking status, systolic blood pressure, use of antihypertensive medications, and prevalent heart failure, myocardial infarction, or stroke at baseline.
Model 3: Model 2 with additional adjustment for heart failure, myocardial infarction, or stroke as time-varying covariates.
*Total WBC Count SD = 1.70 x 10 9 /L