Table 1 Baseline characteristics of breast cancer cases and control subjects
From: SNPs related to vitamin D and breast cancer risk: a case-control study
Factor | Category | Study population with SNP data (%) | Study population with data on vitamin D (%) | ||
|---|---|---|---|---|---|
Control subjects (n = 3193) | Cases (n = 865) | Control subjects (n = 643) | Cases (n = 700) | ||
Age, years | Mean ± SD | 57.4 ± 6.3 | 56.6 ± 7.3 | 57.0 ± 7.3 | 56.9 ± 7.2 |
Season of inclusion in MDCS | January–March | 33.1 | 28.8 | 29.9 | 29.9 |
April–June | 19.0 | 24.7 | 24.0 | 23.9 | |
July–September | 18.0 | 22.8 | 21.3 | 21.9 | |
October–December | 29.9 | 23.7 | 24.9 | 24.4 | |
Education | O-level college (7–9 years) | 73.6 | 66.5 | 68.0 | 67.7 |
A-level college (11–12 years) | 6.8 | 7.1 | 7.3 | 7.3 | |
University | 19.4 | 26.1 | 24.7 | 24.7 | |
Type of occupation | Manual labour worker | 39.6 | 32.7 | 38.7 | 34.4 |
Non-manual labour worker | 52.5 | 60.6 | 53.8 | 58.6 | |
Employer/self-employed | 6.9 | 5.7 | 7.5 | 5.7 | |
Missing | 0.9 | 1.0 | 0.0 | 1.3 | |
Married/co-habitating | No | 31.0 | 33.5 | 32.0 | 34.0 |
Yes | 69.0 | 66.5 | 68.0 | 66.0 | |
Age at menarche, years | < 12 | 6.2 | 7.6 | 4.5 | 7.3 |
12–15 | 67.2 | 67.3 | 68.9 | 67.1 | |
> 15 | 25.6 | 23.9 | 26.0 | 24.4 | |
Missing | 0.9 | 1.2 | 0.6 | 1.1 | |
Parity | Nulliparous | 12.0 | 14.1 | 11.2 | 13.6 |
One child | 21.4 | 19.5 | 22.4 | 19.3 | |
Two children | 40.6 | 44.7 | 40.9 | 44.1 | |
Three children or more | 22.8 | 19.5 | 22.7 | 20.6 | |
Missing | 3.1 | 2.1 | 2.8 | 2.4 | |
Age at first birth, years | Nulliparous | 12.0 | 14.1 | 11.2 | 13.6 |
≤ 20 | 16.5 | 14.9 | 17.9 | 13.6 | |
21–24 | 28.2 | 27.3 | 27.7 | 27.7 | |
25–29 | 29.1 | 28.7 | 28.6 | 30.1 | |
≥ 30 | 11.1 | 12.9 | 11.8 | 12.6 | |
Missing | 3.1 | 2.1 | 2.8 | 2.4 | |
Age at menopause, years | Pre-/peri-menopause | 27.2 | 35.6 | 32.5 | 33.1 |
< 45 | 9.8 | 9.0 | 8.6 | 9.4 | |
45–53 | 45.3 | 39.5 | 42.6 | 41.6 | |
> 53 | 16.0 | 13.8 | 14.9 | 13.7 | |
Missing | 1.7 | 2.1 | 1.4 | 2.1 | |
Exposure to oral contraceptives | No | 54.3 | 45.9 | 50.1 | 48.6 |
Yes | 45.7 | 54.0 | 49.9 | 51.3 | |
Exposure to hormone replacement therapy (HRT) | No (pre-menopausal) | 22.0 | 28.4 | 26.3 | 25.7 |
No (post-menopausal) | 59.8 | 44.5 | 53.3 | 45.7 | |
Oestrogen only | 7.6 | 7.4 | 9.2 | 7.6 | |
Progesterone only | 0.6 | 1.2 | 0.9 | 1.3 | |
Combined HRT | 9.4 | 18.3 | 9.8 | 19.4 | |
Height, m | ≤ 1.59 | 24.6 | 20.6 | 23.2 | 20.3 |
1.60–1.69 | 58.1 | 61.4 | 59.1 | 61.6 | |
≥ 1.70 | 17.2 | 18.0 | 17.7 | 18.1 | |
Body mass index, kg/m2 | < 25 | 53.3 | 50.1 | 51.8 | 50.6 |
≥ 25 to < 30 | 33.6 | 34.5 | 36.1 | 33.3 | |
≥ 30 | 13.0 | 15.5 | 12.1 | 16.1 | |
Alcohol consumption | Not in last year | 11.4 | 9.7 | 11.4 | 10.4 |
Some in last year | 12.7 | 11.2 | 12.4 | 11.4 | |
Some in last month | 75.6 | 78.8 | 75.9 | 78.0 | |
Smoking | Never | 46.8 | 43.0 | 42.5 | 44.0 |
Current | 26.7 | 26.7 | 27.8 | 26.6 | |
Ex-smoker | 26.4 | 30.3 | 29.7 | 29.4 | |