Table I.
Distribution of selected characteristics of cases and controlsa
| Characteristics | Cases (N = 230) | Controls (N = 468) |
|---|---|---|
| mtDNA copy number, median (IQR) | 131 (102–159)b | 120.5 (96–150.5) |
| Age at baselinec, years | ||
| 55–59 | 67 (29.1) | 135 (28.9) |
| 60–64 | 82 (35.7) | 165 (35.3) |
| 65–69 | 51 (22.2) | 114 (24.4) |
| 70–74 | 30 (13.0) | 54 (11.5) |
| Sexc | ||
| Female | 66 (28.7) | 137 (29.3) |
| Male | 164 (71.3) | 331 (70.7) |
| Racec | ||
| White, non-Hispanic | 209 (90.9) | 416 (88.9) |
| Black, non-Hispanic | 10 (4.4) | 26 (5.6) |
| Other | 11 (4.8) | 26 (5.6) |
| BMI, kg/m2 | ||
| <25 | 50 (21.7) | 140 (30.2) |
| 25–30 | 95 (41.3) | 212 (45.8) |
| >30 | 85 (37.0) | 111 (24.0) |
| Missing | 0 | 5 |
| Smoking status | ||
| Never | 92 (40.0) | 212 (45.3) |
| Former | 117 (50.9) | 209 (44.7) |
| Current | 21 (9.1) | 47 (10.0) |
| History of hypertension | ||
| No | 131 (57.2) | 306 (66.0) |
| Yes | 98 (42.8) | 158 (34.1) |
| Missing | 1 | 4 |
| DNA source materialc | ||
| Buffy coat | 208 (90.4) | 422 (90.2) |
| Whole blood | 2 (0.9) | 6 (1.3) |
| Previously extracted DNA | 20 (8.7) | 40 (8.6) |
| Year of blood collectionc, median (range) | 1997 (1993–2002) | 1997 (1994–2002) |
| Season of blood collectionc | ||
| January–April | 67 (29.1) | 133 (28.4) |
| May–August | 83 (36.1) | 172 (36.8) |
| September–December | 80 (34.8) | 163 (34.8) |
| Study year of selected specimenc | ||
| Baseline | 197 (85.7) | 394 (84.2) |
| Otherd | 33 (14.4) | 74 (15.8) |
IQR, interquartile range.
aReported as frequency (%) unless otherwise noted. Missing values are excluded from percentages.
b P = 0.008, Wilcoxon rank-sum test.
cCases and controls were matched on these selected characteristics.
dSpecimens selected from a subsequent annual examination 1–5 years after baseline.