Table 5.

Associations between age at menopause and risk of chronic LBP in HUNT3 in prospective analysis, among women at least 40 years old in HUNT2

	Total number of women in category of age at menopause	Number of women with chronic LBP	Crude AR of chronic LBP (%)	RR (95% CI) with adjustment for age only	RR (95 % CI) with additional adjustment*
Number of women included			5394	5394	4941
Age at menopause (year)
≤40	108	24	22.2	1.06 (0.73 to 1.55)	1.05 (0.70 to 1.57)
41–43	102	26	25.5	1.21 (0.85 to 1.73)	1.10 (0.74 to 1.62)
44–46	308	67	21.8	1.03 (0.80 to 1.34)	1.03 (0.79 to 1.34)
47–49	500	96	19.2	0.91 (0.73 to 1.15)	0.94 (0.74 to 1.19)
50–52	841	155	18.4	0.87 (0.70 to 1.09)	0.86 (0.68 to 1.09)
53–55	368	83	22.6	1.07 (0.82 to 1.40)	1.05 (0.79 to 1.40)
≥56	86	12	14.0	0.66 (0.38 to 1.16)	0.68 (0.37 to 1.26)
Premenopausal	3081	637	20.7	1.00 (reference)	1.00 (reference)
P categorical effect				0.33	0.59
P for linear trend†				0.11	0.31

*Adjustment for age, BMI, physical activity, education, smoking, nulliparity, age at first delivery and age at menarche.

†Among postmenopausal women.

AR, absolute risk; BMI, body mass index; HUNT, Trøndelag Health Study; LBP, low back pain; RR, relative risk.