Table 3 Exogenous oestrogen use and risk of melanoma among women in the NIH-AARP Diet and Health Study

Factor	No. of woman-years^a	No. of cases^a	HR^b (95% CI)	P for trend^c
OC use
Never or <1 year	1,386,881	635	Reference
Ever-users	888,852	408	1.02 (0.89–1.16)
Duration of OC use
Never or <1 years	1,386,881	635	Reference
1–4 years	394,284	166	0.95 (0.80–1.13)
5–9 years	278,949	133	1.06 (0.87–1.28)
≥10 years	215,619	109	1.09 (0.88–1.34)	0.41
MHT use^d
Never	1,034,410	458	Reference
Ever	1,260,650	599	1.02 (0.89–1.15)
Past	212,649	91	0.92 (0.74–1.16)
Current	1,048,001	508	1.04 (0.91–1.18)
MHT duration^d
Never	987,164	437	Reference
<5 years	440,939	188	0.95 (0.80–1.13)
5–9 years	317,187	163	1.10 (0.92–1.33)
≥10 years	504,234	248	1.01 (0.86–1.18)	0.68
MHT in women with natural menopause^d
Never	767,318	334	Reference
Ever	508,536	234	0.99 (0.83–1.18)
Past	107,336	36	0.72 (0.51–1.02)
Current	401,200	198	1.06 (0.88–1.28)
MHT duration^d
Never	744,033	329	Reference
<5 years	253,718	103	0.90 (0.72–1.13)
5–9 years	150,995	76	1.06 (0.82–1.36)
≥10 years	104,202	55	1.01 (0.76–1.35)	0.87
MHT in women with surgical menopause^d
Never	253,152	110	Reference
Ever	749,457	361	1.04 (0.83–1.29)
Past	104,671	54	1.14 (0.82–1.58)
Current	644,786	307	1.02 (0.81–1.28)
MHT duration^d
Never	239,830	106	Reference
5 years	186,471	83	0.98 (0.73–1.31)
5–9 years	165,346	85	1.09 (0.82–1.47)
≥10 years	398,876	193	0.99 (0.77–1.26)	0.99
MHT and OC use^d
Neither or <1-year OC/MHT use	709,283	304	Reference
MHT use only	675,185	329	1.07 (0.91–1.25)
OC use only	309,199	137	1.07 (0.87–1.31)
OC and MHT use	577,907	270	1.06 (0.89–1.26)

CI confidence interval, HR hazard ratio, OC oral contraceptive, MHT menopausal hormone therapy, NIH National Institutes of Health
^aIncludes 167,503 women and 2,299,578 total woman-years, but numbers may be inconsistent because of missing values
^bAdjusted for age, ambient ultraviolet radiation quartile (coded continuously 1–4), education (less than high school, high school, some college, college or graduate school, body mass index (>18.5–<25, 25–<30, 30–<60 kg/m²), smoking status (never, former, current), marriage (married, widowed, divorced/separated, never married), family history of cancer (no, yes), colonoscopy or sigmoidoscopy (no, yes), menopausal hormone therapy (no, yes)
^cTrend tests were conducted by modeling ordinal categories as continuous
^dAdjusted for factors mentioned in Table footnote b except for menopausal hormone therapy (no, yes)

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