Table 1 Baseline demographic and clinical characteristics
|  | All | Serum 25 (OH)D 15–49 nmol/l | Serum 25 (OH)D 50–74 nmol/l | Serum 25 (OH)D 75–150 nmol/l | p value |
|---|---|---|---|---|---|
N | 245 | 89 | 96 | 60 | Â |
Male (%) | 156 (63) | 49 (55) | 66 (69) | 41 (68) | 0.09 |
Age (years) | 67 ± 8 | 67 ± 9 | 67 ± 9 | 67 ± 7 | 0.82 |
White skin colour (%) | 234 (95) | 80 (90) | 93 (97) | 60 (100) | 0.01 |
Diabetes duration (years) | 6.0 (3.0–8.0) | 5.0 (3.5–7.0) | 6.0 (3.0–8.0) | 6.0 (3.0–8.0) | 0.59 |
Antidiabetic treatment | |||||
 Lifestyle adjustments | 11 (5) | 5 (6) | 4 (4) | 2 (3) | 0.55 |
 Metformin | 155 (63) | 50 (56) | 62 (65) | 43 (72) | |
 SU-derivative | 9 (4) | 3 (3) | 4 (4) | 2 (3) | |
 Metformin + SU-derivative | 70 (28) | 31 (35) | 26 (27) | 13 (22) | |
DM-complications (%) | |||||
 Retinopathy | 11 (5) | 5 (6) | 4 (4) | 2 (3) | 0.80 |
 Neuropathy | 32 (13) | 11 (12) | 11 (12) | 10 (17) | 0.63 |
 Microalbuminuria | 30 (12) | 16 (18) | 9 (9) | 5 (8) | 0.13 |
Antihypertensive drugs (%) | |||||
 Diuretics | 88 (36) | 38 (42) | 28 (30) | 22 (37) | 0.20 |
 Calcium channel blockers | 44 (18) | 19 (21) | 14 (15) | 11 (18) | 0.53 |
 ACE inhibitors/AT-II receptor antagonists | 135 (55) | 56 (63) | 45 (47) | 34 (57) | 0.34 |
 Beta blockers | 92 (38) | 35 (39) | 35 (37) | 22 (37) | 0.95 |
Statins (%) | 205 (84%) | 75 (83%) | 80 (84%) | 50 (83%) | 0.99 |
Cardiovascular disease (%) | 67 (27) | 23 (26) | 32 (33) | 12 (20) | 0.16 |
Smoking status | |||||
 Current (%) | 36 (15) | 17 (19) | 12 (12) | 7 (12) | 0.20 |
Alcohol use (%) ≤2 units/day | 216 (89) | 75 (83) | 84 (88) | 66 (92) | 0.03 |
Exposure to sun | |||||
 <5 h/week | 102 (42) | 51 (57) | 36 (37.5) | 15 (25) | <0.001 |
 5–10 h/week | 103 (42) | 33 (37) | 45 (47.9) | 25 (42) | |
 >10 h/week | 40 (16) | 5 (6) | 15 (15.6) | 20 (33) | |
Physical activity | |||||
 <2 h/week | 78 (32) | 38 (43) | 30 (31) | 10 (17) | 0.03 |
 2–5 h/week | 112 (45) | 38 (43) | 46 (48) | 28 (47) | |
 >5 h/week | 55 (23) | 13 (14) | 20 (21) | 22 (36) | |
Season of blood collection | |||||
 Spring | 24 (10) | 10 (11) | 11 (11) | 3 (5) | 0.047 |
 Summer | 66 (27) | 16 (18) | 24 (25) | 26 (43) | |
 Autumn | 119 (48) | 48 (54) | 45 (47) | 26 (43) | |
 Winter | 36 (15) | 15 (17) | 16 (17) | 5 (9) | |
Body mass index (kg/m2) | 28.8 ± 4.5 | 29.9 ± 4.4 | 28.0 ± 4.6 | 28.2 ± 3.9 | 0.009 |
WTH ratio | 0.98 (0.93–1.04) | 0.99 (0.92–1.04) | 0.97 (0.93–1.04) | 1.00 (0.94–1.03) | 0.77 |
AGE-value | 2.64 ± 0.6 | 2.81 ± 0.6 | 2.63 ± 0.6 | 2.41 ± 0.5 | <0.001 |
Fasting glucose (mmol/l) | 7.5 (6.9–8.2) | 7.4 (6.9–8.2) | 7.5 (6.9–8.6) | 7.7 (6.9–8.4) | 0.84 |
Fasting insulin (mU/l) | 14.5 (9.0–21.0) | 14.9 (9.5–21.8) | 13.8 (8.8–21.0) | 14.6 (8.7–20.9) | 0.78 |
HbA1c (mmol/mol) | 51 (47–55) | 51 (49–54) | 52 (45–56) | 51 (46–55) | 0.96 |
HbA1c (%) | 6.8 (6.5–7.2) | 6.8 (6.6–7.1) | 6.9 (6.3–7.3) | 6.8 (6.4–7.2) | 0.96 |
LDL-cholesterol (mmol/l) | 2.5 ± 0.9 | 2.5 ± 1.0 | 2.5 ± 1.0 | 2.4 ± 0.7 | 0.77 |
eGFR (ml/min/1.73 m2) | 81 ± 18 | 82 ± 20 | 81 ± 17 | 82 ± 17 | 0.94 |
Calcium (mmol/l) | 2.33 ± 0.08 | 2.32 ± 0.08 | 2.33 ± 0.08 | 2.34 ± 0.07 | 0.22 |
Albumine (g/l) | 40 (38–41) | 39 (38–41) | 40 (38–41) | 40 (39–41) | 0.07 |
Serum 25(OH)D (nmol/l) | 60.3 ± 23.4 | 36.9 ± 8.0 | 61.5 ± 7.2 | 92.9 ± 13.4 | <0.001 |
PTH (pmol/l) | 5.1 (4.0–6.8) | 5.2 (4.4–7.0) | 5.4 (4.1–6.9) | 4.3 (3.6–5.9) | 0.01 |
AP (U/l) | 72.6 ± 20.6 | 74.6 ± 24.0 | 70.1 ± 19.3 | 73.3 ± 16.6 | 0.38 |