Table 1.

Selected baseline characteristics across 25(OH) vitamin D season-specific quartiles in controls, ATBC Study [presented as medians (IQRs) or percentages]

Q1 (n = 106)Q2 (n = 108)Q3 (n = 105)Q4 (n = 108)P valuea
% Blood collected in winter (November–April)62.362.062.962.01.0
Serum 25(OH)D, nmol/L
 Winter16.7 (12.9–18.9)26.8 (23.8–28.6)36.6 (34.2–39.9)55.5 (49.9–64.9)<0.0001
 Summer25.5 (19.6–27.3)40.2 (37.5–43.0)52.3 (49.6–56.9)71.8 (66.4–81.3)<0.0001
 Age, years57 (53–60)58 (55–61)56 (52–59)58 (56–64)0.03
 BMI, kg/m²26.3 (23.6–29.4)25.6 (24.1–29.5)25.9 (24.1–28.3)25.9 (24.4–28.0)0.94
 % Elementary school education or less77.486.177.169.40.07
 % Currently married82.175.081.083.30.57
 % History of diabetes3.86.52.92.80.52
 Years smoking37 (31–41)36 (30–40)35 (30–40)34 (30–40)0.12
 No. of cigarettes/day20 (15–25)20 (15–25)20 (12–24)20 (15–25)0.32
% Urban residence54.756.565.766.70.03
 % Leisure physical activity ≥1/week41.548.659.154.60.02
Daily dietary intake
 Energy intake, kcal/day2,816 (2,350–3,144)2,694 (2,219–3,182)2,710 (2,250–3,131)2,613 (2,240–3,191)0.76
 Calcium, mg/day1,412 (1,096–1,848)1,375 (1,144–1,650)1,340 (1,065–1,634)1,290 (947–1,637)0.12
 Vitamin D, μg/day3.7 (2.6–5.2)4.7 (3.4–6.6)4.9 (3.2–7.1)6.2 (4.0–8.0)<0.0001
 Alcohol, g/day9.9 (1.7–26.0)11.0 (2.0–30.1)10.7 (3.0–27.4)12.7 (4.4–27.2)0.90
 Coffee, g/day550 (440–880)550 (340–750)550 (330–770)600 (440–770)0.94
Supplement use
 % Calcium (yes)2.88.36.719.40.0001
 % Vitamin D (yes)0.94.64.816.7<0.0001
 % HBsAgb0.00.01.21.20.48
 % Anti-HBcb7.62.310.36.10.17
 % Anti-HCVb0.01.20.00.00.48
  • aWilcoxon tests for continuous variables; Chi-square tests, or Fisher exact test where appropriate, for categorical variables.

  • bAmong 347 controls who had information on HBsAG, anti-HBc, and anti-HCV.