TABLE 1.
Age-standardized characteristics of men and women from the training and testing sets in the NHS and the HPFS1
| NHS |
HPFS |
|||
| Training set | Testing set | Training set | Testing set | |
| Participants, n | 1268 | 317 | 351 | 87 |
| Fasting plasma homocysteine,2,3 μmol/L | 10.7 (8.8–12.9) | 10.7 (8.8–13.2) | 14.1 (11.3–16.0) | 13.3 (11.0–16.2) |
| Age at blood draw,2 y | 59.3 ± 7 | 59.2 ± 7 | 63.8 ± 9.0 | 64.8 ± 10.4 |
| BMI, kg/m2 | 25 ± 4 | 25 ± 4 | 25 ± 3 | 25 ± 3 |
| Physical activity,4 MET/wk | 16 ± 19 | 16 ± 17 | 31 ± 30 | 36 ± 31 |
| Current smokers, % | 20 | 19 | 7 | 7 |
| Current multivitamin users, % | 42 | 44 | 55 | 55 |
| Nondrinkers of alcohol, % | 36 | 38 | 23 | 22 |
| Mean dietary intake5 | ||||
| Total calorie intake, kcal/d | 1759 ± 487 | 1733 ± 472 | 1938 ± 587 | 1947 ± 584 |
| Caffeine, mg/d | 265 ± 225 | 227 ± 208 | 204 ± 209 | 280 ± 246 |
| Alcohol among drinkers, g/d | 9 ± 11 | 10 ± 12 | 15 ± 16 | 14 ± 14 |
| Total folate, μg/d | 442 ± 229 | 445 ± 210 | 572 ± 345 | 625 ± 348 |
| Total riboflavin, mg/d | 4 ± 7 | 5 ± 15 | 6 ± 22 | 6 ± 11 |
| Total pyridoxin, mg/d | 8 ± 24 | 9 ± 27 | 12 ± 40 | 18 ± 48 |
| Total cyanocobalamin, μg/d | 10 ± 10 | 11 ± 16 | 14 ± 24 | 13 ± 11 |
| Total betaine, mg/d | 110 ± 44 | 106 ± 39 | 137 ± 75 | 138 ± 51 |
| Total choline, mg/d | 312 ± 53 | 316 ± 52 | 366 ± 69 | 372 ± 55 |
| Methionine, mg/d | 2 ± 0.4 | 2 ± 0.3 | 2 ± 0.5 | 2 ± 0.4 |
1
Values are means ± SDs unless otherwise specified. HPFS, Health Professionals Follow-Up Study; MET, metabolic equivalent; NHS, Nurses’ Health Study.
2
Values are not age-adjusted.
3
Values are medians (IQRs).
4
Estimated as the sum of the average time per week spent in each activity × the MET value for that activity. MET is defined as the ratio of the work metabolic rate to the resting metabolic rate [(caloric need per kilogram body weight per hour activity)/(caloric need per kilogram body weight per hour at rest)].
5
Nutrient values are energy-adjusted intake.