TABLE 1.
Baseline characteristics of study participants in 2 prospective, nested, case-control studies of incident stroke (n = 594 cases and 594 matched controls) in the NHS, 1990, and HPFS, 19941
| NHSM |
HPFS |
|||
| Characteristics2 | Cases (n = 472) | Controls (n = 472) | Cases (n = 122) | Controls (n = 122) |
| Stroke types, n (%) | ||||
| Ischemic | 371 (78.6) | — | 80 (65.6) | — |
| Hemorrhagic | 101 (21.4) | — | 21 (17.2) | — |
| Undefined | 0 (0) | — | 21 (17.2) | — |
| Age, y [0]3 | 61.0 ± 6.14 | 61.0 ± 6.1 | 67.6 ± 7.9 | 67.6 ± 7.8 |
| Race-ethnicity,3 % [10] | ||||
| White | 98.1 | 98.9 | 94.3 | 94.3 |
| African-American | 0.9 | 0.4 | 0.0 | 0.0 |
| Asian/other | 1.1 | 0.6 | 5.7 | 5.7 |
| BMI, kg/m2 [12] | 25.7 ± 4.9 | 25.4 ± 4.8 | 26.2 ± 3.2 | 26.2 ± 3.2 |
| BMI, % [12] | ||||
| Normal | 50.5 | 55.2 | 35.8 | 33.6 |
| Overweight | 35.0 | 31.3 | 49.2 | 53.5 |
| Obese | 14.4 | 13.4 | 15.0 | 12.9 |
| Smoking status,3 % [11] | ||||
| Current smoker | 16.5 | 16.6 | 6.7 | 5.0 |
| Past smoker | 40.0 | 39.6 | 52.5 | 52.9 |
| Never smoker | 43.6 | 43.8 | 40.8 | 42.0 |
| Physical activity, MET-h/wk [10] | 15.2 ± 18.5 | 16.8 ± 18.8 | 32.5 ± 36.6 | 35.8 ± 44.6 |
| Medical history, % | ||||
| Hypertension [0] | 31.6* | 22.0 | 42.6* | 22.1 |
| Hypercholesterolemia [0] | 39.2 | 33.1 | 29.5 | 19.7 |
| Parental MI before 60 y [73] | 19.8 | 21.9 | 12.5 | 7.4 |
| Family history of diabetes [1] | 32.2 | 29.2 | 32.8 | 26.5 |
| Plasma fatty acids, % of total fatty acids (total n = 1188) | ||||
| 14:0 | 0.70 ± 0.40* | 0.66 ± 0.37 | 0.91 ± 0.42 | 0.85 ± 0.41 |
| 15:0 | 0.17 ± 0.05 | 0.17 ± 0.05 | 0.19 ± 0.06 | 0.19 ± 0.05 |
| 17:0 | 0.33 ± 0.08 | 0.33 ± 0.07 | 0.32 ± 0.06 | 0.34 ± 0.07 |
| trans 16:1n−7 | 0.22 ± 0.08 | 0.22 ± 0.08 | 0.20 ± 0.07 | 0.22 ± 0.07 |
| RBC fatty acids, % of total fatty acids (total n = 1150) | ||||
| 14:0 | 0.45 ± 0.34 | 0.46 ± 0.42 | 0.42 ± 0.27 | 0.41 ± 0.29 |
| 15:0 | 0.14 ± 0.09 | 0.13 ± 0.05 | 0.11 ± 0.05 | 0.11 ± 0.05 |
| 17:0 | 0.50 ± 0.19 | 0.50 ± 0.18 | 0.47 ± 0.15 | 0.48 ± 0.15 |
| trans 16:1n−7 | 0.17 ± 0.06 | 0.17 ± 0.06 | 0.14 ± 0.05 | 0.14 ± 0.05 |
| Diet, servings/d | ||||
| Total dairy [25] | 2.1 ± 1.5 | 2.2 ± 1.4 | 2.2 ± 1.8 | 2.3 ± 1.7 |
| Whole-fat dairy [29] | 0.93 ± 1.17 | 0.90 ± 1.02 | 1.1 ± 1.3 | 1.2 ± 1.4 |
| Low-fat dairy [28] | 1.2 ± 1.1 | 1.3 ± 1.1 | 1.2 ± 1.1 | 1.1 ± 1.1 |
| Processed meats [24] | 0.21 ± 0.29 | 0.22 ± 0.30 | 0.35 ± 0.40 | 0.41 ± 0.65 |
| Unprocessed meats [24] | 0.91 ± 0.50 | 0.91 ± 0.48 | 0.90 ± 0.59 | 0.98 ± 0.52 |
| Fruit and vegetables [24] | 5.5 ± 2.9 | 5.6 ± 2.7 | 5.8 ± 3.1 | 5.7 ± 3.2 |
| Fish [26] | 0.32 ± 0.27 | 0.31 ± 0.27 | 0.23 ± 0.21 | 0.24 ± 0.23 |
| Alcohol [29] | 0.45 ± 0.84 | 0.45 ± 0.84 | 0.97 ± 1.36 | 0.80 ± 1.21 |
*P < 0.05 for the difference in characteristics between cases and controls. The paired t test was used to compute P values for differences in continuous characteristics between cases and their matched controls. The McNemar-Bowker test was used to compare corresponding proportions for dichotomous 2-group variables, such as hypertension (yes or no), and 3-group variables, such as BMI (normal, overweight, or obese), respectively. HPFS, Health Professionals Follow-Up Study; MET-h, metabolic equivalent task-hours; MI, myocardial infarction; NHS, Nurses’ Health Study; RBC, red blood cell.
Few participants (n < 15) had missing values for each variable except for parental history of MI in the NHS (missing n = 70). Values in square brackets represent overall numbers missing for variables.
Matching factors; other matching factors included blood collection date and follow-up years.
Mean ± SD (all such values).