Table 1 Baseline characteristics by quartiles of vitamin D levels in the 2011–2012 wave
Characteristics | All participants | Plasma 25(OH) D concentrations | P value | |||
|---|---|---|---|---|---|---|
Quartile 1 (< 31.78 nmol/L) | Quartile 2 (31.78–43.65 nmol/L) | Quartile 3 (43.65–56.61 nmol/L) | Quartile 4 (≥56.61 nmol/L) | |||
Age, median (IQR), years | 79 (71, 87) | 81 (71, 91) | 80 (72, 86) | 79 (71, 86) | 77 (70, 85) | 0.012 |
Female, no. (%) | 498 (46.4) | 163 (60.8) | 132 (49.1) | 115 (42.9) | 88 (32.7) | < 0.001 |
Married, no. (%) | 583 (54.3) | 121 (45.2) | 146 (54.3) | 153 (57.1) | 163 (60.6) | 0.003 |
Rural, no. (%) | 880 (81.9) | 221 (82.5) | 202 (75.1) | 221 (82.5) | 236 (87.7) | 0.002 |
Education (≥ 1 year), no. (%) | 512 (47.7) | 100 (37.3) | 124 (46.1) | 137 (51.1) | 151 (56.1) | < 0.001 |
With household member(s), no. (%) | 816 (76.0) | 203 (75.8) | 206 (76.6) | 206 (76.9) | 201 (74.7) | 0.938 |
Economic independence, no. (%) | 373 (34.7) | 93 (34.7) | 96 (35.7) | 87 (32.5) | 97 (36.1) | 0.819 |
Smoking status | Â | Â | Â | Â | Â | 0.001 |
 Current | 843 (78.5) | 230 (85.8) | 217 (80.7) | 201 (75.0) | 195 (72.5) |  |
 Never or former | 231 (21.5) | 38 (14.2) | 52 (19.3) | 67 (25.0) | 74 (27.5) |  |
Drinking status |  |  |  |  |  | < 0.001 |
 Current | 866 (80.6) | 229 (85.5) | 229 (85.1) | 213 (79.5) | 195 (72.5) |  |
 Never or former | 208 (19.4) | 39 (14.6) | 40 (14.9) | 55 (20.5) | 74 (27.5) |  |
Regular exercise | 207 (19.3) | 42 (15.7) | 50 (18.6) | 56 (20.9) | 59 (21.9) | 0.262 |
Natural tooth number, no. | Â | Â | Â | Â | Â | 0.905 |
 < 20 | 748 (69.7) | 191 (71.3) | 185 (68.8) | 184 (68.7) | 188 (69.9) |  |
 ≥20 | 326 (30.4) | 77 (28.7) | 84 (31.2) | 84 (31.3) | 81 (30.1) |  |
Total sleep time (h) | Â | Â | Â | Â | Â | 0.226 |
 ≤5 | 179 (16.7) | 44 (16.4) | 37 (13.8) | 40 (14.9) | 58 (21.6) |  |
 6–8 | 708 (65.9) | 178 (66.4) | 179 (66.5) | 182 (67.9) | 169 (62.8) |  |
 ≥9 | 187 (17.4) | 46 (17.2) | 53 (19.7) | 46 (17.2) | 42 (15.6) |  |
BMI (kg/m2) | Â | Â | Â | Â | Â | 0.512 |
 < 18.5 | 191 (17.8) | 45 (16.8) | 44 (16.4) | 42 (15.7) | 60 (22.3) |  |
 18.5–24 | 615 (57.3) | 156 (58.2) | 153 (56.9) | 160 (59.7) | 146 (54.3) |  |
 24–28 | 209 (19.5) | 52 (19.4) | 57 (21.2) | 55 (20.5) | 45 (16.7) |  |
 ≥28 | 59 (5.5) | 15 (5.6) | 15 (5.6) | 11 (4.1) | 18 (6.7) |  |
Calf circumference (< 31 cm) | 524 (48.8) | 144 (53.7) | 144 (53.5) | 127 (47.4) | 109 (40.5) | 0.006 |
Prefrail | 446 (41.5) | 139 (51.9) | 113 (42.0) | 96 (35.8) | 98 (36.4) | < 0.001 |
Season of blood draw |  |  |  |  |  | < 0.001 |
 Spring (March–May) | 263 (24.5) | 108 (40.3) | 65 (24.2) | 48 (17.9) | 42 (15.6) |  |
 Summer (June–August) | 745 (69.4) | 158 (59.0) | 201 (74.7) | 204 (76.1) | 182 (67.7) |  |
 Autumn (September–November) | 66 (6.2) | 2 (0.8) | 3 (1.1) | 16 (6.0) | 45 (16.7) |  |
25(OH) D (nmol/L) | 43.65 (31.78, 56.61) | 25.83 (21.26, 28.84) | 37.29 (34.10, 40.73) | 49.70 (46.65, 52.80) | 67.21 (61.15, 75.95) | < 0.001 |
Albumin (g/L) | 41.36 (38.40, 44.30) | 40.50 (37.20, 43.48) | 41.90 (39.10, 44.60) | 41.50 (38.30, 44.88) | 41.40 (38.90, 44.00) | 0.002 |
hs-CRP (mg/L) | 0.79 (0.37, 1.90) | 0.86 (0.38, 2.08) | 0.72 (0.34, 1.72) | 0.80 (0.38, 1.83) | 0.81 (0.38, 1.99) | 0.444 |