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Table 1 Median 25(OH)D concentrations (nmol/L) of the sample, by potential influential factors

From: Association between serum 25-hidroxyvitamin D concentrations and ultraviolet index in Portuguese older adults: a cross-sectional study

Variable n Median (Q1; Q3) P-value
Sex    < 0.001
 Female 872 32.95 (19.45; 52.88)  
 Male 625 45.58 (26.10; 61.80)  
Age (years)    < 0.001
 65–69 412 44.35 (29.95; 63.98)  
 70–74 372 38.35 (25.60; 58.68)  
 75–79 319 34.20 (20.20; 58.30)  
  ≥ 80 394 24.85 (14.50; 44.83)  
NUTS II    < 0.001
 North 468 35.50 (20.35; 58.40)  
 Center 391 31.50 (17.20; 50.80)  
 Lisbon Metropolitan Area 383 42.20 (28.80; 62.30)  
 Alentejo 136 30.60 (22.15; 51.48)  
 Algarve 65 36.30 (20.75; 55.20)  
 Madeira 30 54.45 (39.23; 74.85)  
 Azores 24 42.75 (21.10; 59.88)  
Education (years)    < 0.001
 0 212 23.80 (13.53; 35.20)  
 1–4 1029 36.90 (21.95; 57.10)  
 5–12 188 44.95 (29.18; 65.63)  
  ≥ 13 68 46.30 (31.18; 74.88)  
Professionally active    0.038
 No 1462 35.75 (21.58; 57.15)  
 Yes 30 46.55 (29.33; 65.60)  
Marital status    < 0.001
 Single, divorced or widowed 796 29.85 (17.30; 48.20)  
 Married or common-law marriage 700 43.40 (28.63; 64.10)  
Residence    < 0.001
 Home 1425 36.80 (22.35; 58.00)  
 Institution 72 17.90 (10.23; 38.28)  
Household income (€)    < 0.001
  < 500 248 29.95 (17.48; 44.93)  
 500–999 305 36.40 (24.15; 58.70)  
  ≥ 1000 174 48.55 (33.65; 69.88)  
 Doesn’t declare/Doesn’t know 770 35.30 (19.90; 56.95)  
Skin phenotype    0.064
 I + II 305 37.30 (24.85; 51.90)  
 III + IV 1109 36.30 (21.30; 59.15)  
 V + VI 80 30.00 (18.95; 46.33)  
Cognitive performance (MMSE)    < 0.001
 Maintenance 1398 36.50 (22.10; 58.43)  
 Impairement 99 28.10 (13.60; 45.90)  
Smoking habits    0.850
 No 1429 35.90 (21.75; 57.40)  
 Yes 68 36.15 (22.65; 51.83)  
Alcoholic beverages consumption    < 0.001
 Does not drink 952 32.95 (20.33; 51.78)  
 Moderate 388 43.85 (24.33; 64.63)  
 Heavy 155 41.80 (27.80; 61.10)  
Physical activity (IPAC)    < 0.001
 Normal 1234 38.30 (23.60; 59.00)  
 Low 261 25.60 (14.85; 47.75)  
Adherence to Mediterranean diet (PREDIMED)    0.001
 Low 849 34.20 (20.40; 54.70)  
 High 648 39.05 (23.63; 60.30)  
Fish/shellfish consumption ≥ 3 servings/week    0.150
 No 372 37.00 (23.70; 60.45)  
 Yes 1125 35.50 (21.00; 56.30)  
Self-perceived health    < 0.001
 Very good 69 44.30 (32.50; 64.20)  
 Good 409 42.20 (24.40; 62.60)  
 Moderate 730 35.30 (22.30; 57.10)  
 Bad 232 28.30 (15.50; 44.23)  
 Very bad 53 25.50 (17.25; 47.55)  
Supplement intake    <0.001
 No 1369 34.90 (20.95; 54.85)  
 Yes 128 54.55 (35.53; 82.78)  
Undernutrition status (MNA-SF)    <0.001
 Without undernutrition 1256 37.50 (22.50; 58.88)  
 Undernourished/at risk of undernutrition 241 29.00 (16.90; 47.65)  
Body mass index    <0.001
 Underweight 3 38.20 (21.90; a)  
 Normal range 248 42.75 (23.25; 65.38)  
 Overweight 660 38.55 (23.53; 60.60)  
 Obese 582 31.20 (19.10; 50.10)  
mUVI categories    < 0.001
 Low 570 30.05 (17.10; 48.50)  
 Moderate 518 32.30 (19.88; 50.88)  
 High 222 45.55 (29.88; 65.00)  
 Very high 187 52.00 (39.00; 69.80)  
Period of blood collection    < 0.001
 December – March 807 28.10 (16.70; 46.40)  
 April – June 690 45.45 (30.40; 66.30)  
  1. n number of subjects (does not always ad up to 1497 because of missing data). Q1: first quartile; Q3: third quartile
  2. P-value for Mann-Whitney dichotomous variables or Kruskal-Wallis test for variables with > 2 categories
  3. aQ3 was not possible to calculate