Table 1 Characteristics of the study population according to the presence and absence of vitamin D deficiency

n

10,990 (36.3)

19,252 (63.7)

Age (years)

46 ± 16

51 ± 16

 < 0.0001

Women

7,388 (67.2)

9,784 (50.8)

 < 0.0001

Education level

 < 0.0001

 Less than elementary school

2,277 (20.7)

5,457 (28.4)

 Middle school

999 (9.1)

2,316 (12.0)

 High school

3,992 (36.3)

6,283 (32.6)

 College or graduate school

3,722 (33.9)

5,196 (27.0)

Residential region

 < 0.0001

 Urban

8,202 (74.6)

12,199 (63.4)

 Rural

2,788 (25.4)

7,053 (36.6)

Smoking

 < 0.0001

 Current smoker

2,234 (20.3)

4,365 (22.7)

 Former smoker

1,635 (14.9)

4,350 (22.6)

 Never

7,121 (64.8)

10,537 (54.7)

Alcohol consumption (times/month)

 < 0.0001

 Never

3,244 (29.5)

5,191 (27.0)

  ≤ 1

3,572 (32.5)

5,108 (26.5)

 2–3

3,637 (33.1)

7,290 (37.9)

  ≥ 4

537 (4.9)

1,663 (8.64)

Physical activity

 < 0.0001

 Yes

4,022 (36.6)

8,240 (42.8)

 No

6,968 (63.4)

11,012 (57.2)

Body mass index (kg/m²)

23.5 ± 3.5

23.8 ± 3.2

 < 0.0001

Obesity status

 < 0.0001

 Normal

5,296 (48.2)

8,152 (42.3)

 Overweight

2,473 (22.5)

4,730 (24.6)

 Obesity

3,221 (29.3)

6,370 (33.1)

Serum vitamin D (25(OH)D) level

11.8 ± 2.2

21.6 ± 5.5

 < 0.0001

Air pollutant level, mean (median)

 PM₁₀ (μg/m³)

50.6 (49)

50.2 (49)

 < 0.0001

 NO₂ (ppb)

26.1 (28)

24.3 (23)

 < 0.0001

 CO (ppm)

0.5 (0.6)

0.5 (0.5)

 < 0.0001