Table 1.
Characteristics of the Study Population
| Variables | All Participants (n = 1766) | Cognitively Normal (n = 1554) | Cognitively Impaired (n = 212) | P Valuea |
|---|---|---|---|---|
| Quartiles of serum 25(OH)D, n (%) | <.001 | |||
| First (8–30 nmol/L) | 458 (25.9) | 358 (23.0) | 100 (47.2) | |
| Second (31–44 nmol/L) | 453 (25.7) | 398 (25.6) | 55 (25.9) | |
| Third (45–65 nmol/L) | 423 (24.0) | 391 (25.2) | 32 (15.1) | |
| Fourth (66–170 nmol/L) | 432 (24.5) | 407 (26.2) | 25 (11.8) | |
| Additional variables | ||||
| Mean age (SD), years | 78.2 (8.6) | 77.6 (8.5) | 83.3 (7.9) | <.001 |
| Women, n (%) | 1058 (59.9) | 914 (58.8) | 144 (67.9) | .011 |
| No educational qualifications, n (%) | 1191 (67.4) | 1015 (65.3) | 176 (82.0) | <.001 |
| White ethnic origin, n (%) | 1738 (98.5) | 1533 (98.8) | 205 (96.7) | .029 |
| Current smokers, n (%) | 206 (11.7) | 182 (11.7) | 24 (11.3) | 1.000 |
| Alcohol consumption, n (%) | <.001 | |||
| 0 g/d | 436 (24.7) | 347 (22.3) | 89 (42.0) | |
| 0.1–29.9 g/d | 1236 (70.0) | 1121 (72.1) | 115 (54.3) | |
| ≥30 g/d | 94 (5.3) | 86 (5.5) | 8 (3.8) | |
| Psychiatric morbidity,b n (%) | 278 (15.3) | 237 (15.3) | 41 (19.3) | .132 |
| Impaired mobility, n (%) | 739 (41.9) | 616 (39.6) | 123 (58.0) | <.001 |
| Hypoalbuminemia, n (%) | 113 (6.4) | 91 (5.9) | 22 (10.4) | .016 |
| Stroke, n (%) | 168 (9.5) | 128 (8.2) | 40 (18.9) | <.001 |
| Heart disease, n (%) | 249 (14.1) | 219 (14.1) | 30 (14.2) | 1.000 |
| Diabetes, n (%) | 154 (8.7) | 129 (8.3) | 25 (11.8) | .093 |
| Hypertension, n (%) | 358 (20.3) | 306 (19.7) | 52 (24.5) | .102 |
| Mean BMI (SD)c, kg/m2 | 27.0 (4.7) | 27.2 (4.6) | 25.2 (5.0) | <.001 |
| Season tested, n (%) | .002 | |||
| Winter (Dec–Feb) | 378 (21.4) | 347 (22.3) | 31 (14.6) | |
| Spring (Mar–May) | 440 (24.9) | 368 (23.7) | 72 (34.0) | |
| Summer (Jun–Aug) | 406 (23.0) | 365 (23.5) | 41 (19.3) | |
| Autumn (Sep–Nov) | 542 (30.7) | 474 (30.5) | 68 (32.1) | |
Abbreviations: 25(OH)D, 25-hydroxyvitamin D; BMI, body mass index.
a
P value for group difference between cognitively normal and cognitively impaired participants.
b
Four or more symptoms on the 12-item General Health Questionnaire.29
c
Available for a subsample of 1279 participants.