Table 5.

Hazard ratio (95% confidence interval) of total knee replacement according to age at menopause and use of hormone replacement therapy among postmenopausal women (n=25,435).

		Model 1†	Model 2††	BMI < 23 kg/m2††		BMI ≥23 kg/m2††
	Cases	HR (95% CI)	HR (95% CI)	Cases	HR (95% CI)	Cases	HR (95% CI)
Age at menopause
<40 years	47	1.00	1.00	11	1.00	36	1.00
40–44 years	91	0.75 (0.53–1.07)	0.74 (0.52–1.05)	17	0.55 (0.26–1.17)	74	0.79 (0.53–1.18)
45–49 years	401	0.90 (0.67–1.22)	0.87 (0.64–1.18)	102	0.85 (0.46–1.59)	299	0.89 (0.63–1.27)
50–54 years	726	1.03 (0.77–1.39)	0.99 (0.73–1.33)	165	0.88 (0.48–1.63)	561	1.03 (0.73–1.44)
≥55 years	101	0.92 (0.65–1.30)	0.88 (0.62–1.25)	18	0.64 (0.30–1.36)	83	0.95 (0.64–1.41)
P for trend§		0.051	0.11		0.83		0.11
P for interaction (BMI category and age at menopause)				0.83
Use of hormone replacement therapy
Never	1277	1.00	1.00	285	1.00	992	1.00
Ever	89	1.07 (0.86–1.34)	1.08 (0.87–1.36)	28	1.21 (0.80–1.82)	61	1.06 (0.81–1.38)
P for interaction (BMI category and use of hormone therapy)				0.79

^†Multivariable model 1: adjusted for age at interview, dialect, year of interview, educational level, smoking status, body mass index, total physical activity duration, sleep duration and sitting duration, baseline history of self-reported, diabetes, hypertension, coronary artery disease, and stroke;

^††Multivariable model 2: further adjusted for number of children, age at menarche, oral contraceptive use (model for age at menarche), hormone replacement therapy use (model for age at menopause) and age at menopause (model for use of hormone replacement therapy).

^§Linear trend was tested by treating the categories as a continuous variable.