Table 3 Individual background factors and risk of first incident fracture

Age at baseline

(years)

18,293

1.06

1.06–1.06

< 0.001

Body mass index (BMI)

(kg/m²)

18,293

0.98

0.97–0.98

< 0.001

Previous fracture

(yes)

18,293

1.80

1.59–2.03

< 0.001

Current smoking

(yes)

17,290

1.14

1.08–1.21

< 0.001

Living alone

(yes)

17,286

1.07

1.01–1.13

0.024

Family history of fractures

(yes)

18,293

1.16

1.09–1.23

< 0.001

Weight at baseline

(kg)

18,293

1.01

1.01–1.02

< 0.001

Highest level of education

17,249

 Completed elementary school

Reference

 Elementary and junior school (6–10 years)

0.88

0.67–1.16

0.371

 Advanced level and university (> 11 years)

0.90

0.68–1.19

0.444

Weight change since 20 years of age

17,259

 It has been the same

Reference

 Gradually increased

1.03

0.94–1.12

0.565

 Gradually decreased

1.38

1.19–1.61

< 0.001

 My weight has varied

1.10

1.01–1.21

0.032

Alcohol

(g/day)

17,072

 Quartile 1 (0–0.80)

Reference

 Quartile 2 (0.81–5.35)

0.94

0.87–1.01

0.079

 Quartile 3 (5.36–11.42)

0.87

0.81–0.94

< 0.001

 Quartile 4 (> 11.43)

0.94

0.87–1.02

0.123

Age at menarche

(years)

17,161

  < 11

0.97

0.87–1.09

0.642

 12–15

Reference

  > 16

1.08

0.99–1.18

0.084

Number of born children

16,999

 no children

Reference

 1–2 children

0.92

0.85–0.995

0.038

  ≥ 3 children

0.97

0.88–1.06

0.428

Total duration of lactation

(months)

18,293

 no lactation

Reference

 1–6

0.89

0.84–0.96

0.001

 7–18

0.91

0.86–0.97

0.006

  ≥ 19

0.89

0.81–0.99

0.029

Age at first delivery

(years)

14,777

  ≤ 19

1.002

0.92–1.10

0.973

 20–34

Reference

  ≥ 35

0.99

0.85–1.16

0.886

Ever use of oral contraceptives

(yes)

17,277

0.96

0.91–1.02

0.227

Total use of oral contraceptives

(years)

8199

  < 10

Reference

 11–19

0.95

0.85–1.05

0.302

  > 20

0.90

0.80–1.01

0.067

Start use of oral contraceptives at age

8316

0.99

0.98–1.001

0.089

Age at menopause

(years)

12,444

  < 40

1.05

0.90–1.22

0.544

 40–44

1.14

1.04–1.26

0.008

 45–54

Reference

  > 55

0.96

0.87–1.06

0.384

Total use of menopausal hormone therapy

(years)

1761

0.99

0.97–1.01

0.209