Table 4 Results of a multiple linear regression analysis on determinants of serum 25(OH)D in women (n = 3,004)

Intercept

51.535

2.946

0.000

Age (per year)

−0.132

0.032

0.000

Season (ref. winter)

 Spring

5.860

1.182

0.000

 Summer

24.515

1.269

0.000

 Autumn

16.847

1.118

0.000

Latitude (ref. 52°-54°)

 47°-49°

4.286

1.137

0.000

 50°-51°

−0.005

1.050

0.996

Vitamin D intake index (ref. low intake)

 Intermediate intake

−0.378

0.979

0.700

 Higher intake

2.013

1.041

0.053

Vitamin D supplement use

13.015

1.816

0.000

Oral contraceptive use

7.081

1.252

0.000

Use of postmenopausal hormone therapy

3.572

2.154

0.097

Body Mass Index (kg/m²)

−0.709

0.081

0.000

Socio-economic status (ref. low)

 Middle

4.467

1.116

0.000

 High

4.575

1.405

0.001

Sport activity (ref. no activity)

 <2 h per week

2.676

0.971

0.006

 > = 2 h per week

7.243

1.171

0.000

Media use (ref. up to 1 h per day)

TV, DVD, video

 1- < 3 h

−0.773

1.134

0.495

 > = 3 h

−2.294

1.564

0.142

Computer, Internet, computer games, game consoles

 1- < 3 h

−1.005

1.094

0.359

 > = 3 h

−4.861

1.904

0.011

Residential traffic

Living near a road with…

(ref. very little traffic)

 Fair amount or quite a lot of traffic

−0.433

0.938

0.644

 Heavy or extremely heavy traffic

−2.076

1.096

0.058

corr. r² = 0.226