Baseline mean values and category percentages for potential confounders, by age at menarche and menopause
| Age at menarche (year)* | Age at menopause (year)† | ||||||||
| ≤11 | 12–13 | 14–15 | ≥16 | ≤46 | 47–49 | 50–52 | ≥53 | Premenopausal | |
| Number of women included | 2288 | 12 176 | 9388 | 1099 | 1044 | 972 | 1579 | 826 | 5633 |
| Age in HUNT2‡ (year) | 41.1 | 41.8 | 45.9 | 47.6 | 55.9 | 56.3 | 58.4 | 60.2 | 45.8 |
| BMI‡ (kg/m2) | 27.1 | 26.0 | 25.5 | 24.9 | 26.6 | 26.8 | 26.9 | 27.5 | 25.9 |
| Physical activity per week§ (%) | |||||||||
| <1 hour hard | 73 | 74 | 78 | 78 | 85 | 84 | 86 | 85 | 76 |
| 1–2 hours hard | 19 | 19 | 16 | 15 | 11 | 12 | 11 | 11 | 18 |
| ≥3 hours hard | 8 | 7 | 6 | 7 | 4 | 4 | 4 | 4 | 6 |
| Cigarette smoking§ (%) | |||||||||
| Never | 39 | 43 | 42 | 43 | 31 | 38 | 45 | 51 | 35 |
| Daily former | 25 | 25 | 27 | 28 | 28 | 28 | 30 | 32 | 30 |
| Daily current | 37 | 33 | 32 | 29 | 41 | 35 | 26 | 17 | 34 |
| Education§ (year) (%) | |||||||||
| ≤9 | 24 | 27 | 35 | 40 | 56 | 54 | 58 | 58 | 27 |
| 10–12 | 48 | 47 | 43 | 38 | 29 | 33 | 27 | 27 | 46 |
| ≥13 | 28 | 25 | 22 | 22 | 14 | 13 | 15 | 15 | 27 |
| Nulliparity§ (%) | 15 | 15 | 12 | 11 | 7 | 6 | 6 | 3 | 5 |
| Age at first childbirth‡, ¶ (year) | 22.6 | 22.8 | 23.1 | 24.0 | 23.1 | 23.2 | 23.3 | 23.2 | 22.9 |
*Among women with information about chronic LBP, BMI, physical activity, education, smoking, nulliparity, age at first delivery and age at menarche.
†Among women at least 40 years old in HUNT2 with information about chronic LBP, BMI, physical activity, education, smoking, nulliparity, age at first delivery and age at menarche and menopause.
‡Mean value within category of age at menarche or menopause.
§Percentages of categories for potential confounder within category of age at menarche or menopause.
¶Among women with at least one child.
BMI, body mass index; HUNT, Trøndelag Health Study; LBP, low back pain.