Table 1

Baseline mean values and category percentages for potential confounders, by age at menarche and menopause

Age at menarche (year)*Age at menopause (year)†
≤1112–1314–15≥16≤4647–4950–52≥53Premenopausal
Number of women included228812 17693881099104497215798265633
Age in HUNT2‡ (year)41.141.845.947.655.956.358.460.245.8
BMI‡ (kg/m2)27.126.025.524.926.626.826.927.525.9
Physical activity per week§ (%)
<1 hour hard737478788584868576
1–2 hours hard191916151112111118
≥3 hours hard876744446
Cigarette smoking§ (%)
Never394342433138455135
Daily former252527282828303230
Daily current373332294135261734
Education§ (year) (%)
≤9242735405654585827
10–12484743382933272746
≥13282522221413151527
Nulliparity§ (%)1515121176635
Age at first childbirth‡, ¶ (year)22.622.823.124.023.123.223.323.222.9
  • *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.