Table 2

Crude incidence rates (IRs), age adjusted incidence rate ratios (IRRs), and 95% confidence intervals (95% CI) for time to perimenopause, stratified by demographic and reproductive characteristics, among 603 women from the Harvard Study of Moods and Cycles, Boston, Massachusetts, 1996–2000

Demographic and reproductive characteristics	Total	Number of women reaching perimenopause	Woman years of follow up	Crude IR (cases/1000 woman years)	Age adjusted IRR† (95% CI)
*Women of colour: Hispanic: 3=white, 3=not specified; not Hispanic: 9=black, 7=Chinese, 2=Japanese, 1=Asian Indian, 4=Native American, 4=not specified. †Estimated using Cox proportional hazards model with time to perimenopause data, stratified by age at baseline in one year intervals. ‡Defined as having a mother or sister with natural menopause before age 46 years.
Age at baseline (y)
36–37	90	19	192	99	1.00
38–39	162	34	352	97	0.97 (0.55 to 1.70)
40–41	137	45	294	153	1.54 (0.90 to 2.54)
42–43	153	53	319	166	1.68 (0.99 to 2.84)
44–45	61	26	119	218	2.25 (1.24 to 4.06)
					p for trend: <0.001
Age at menarche (y)
<12	99	26	216	121	1.00
12–14	438	130	929	140	1.18 (0.77 to 1.79)
>14	66	21	131	160	1.50 (0.84 to 2.68)
Parity
Nulliparous	206	54	439	123	1.00
1–2 livebirths	284	85	598	142	1.07 (0.76 to 1.52)
≥3 livebirths	113	38	238	159	1.23 (0.81 to 1.88)
Oral contraceptive use
Never use	183	53	390	136	1.00
1–5 years	295	90	624	144	0.95 (0.67 to 1.35)
6–11 years	85	19	184	103	0.72 (0.43 to 1.23)
>11 years	40	15	78	192	1.34 (0.75 to 2.40)
Race/ethnicity*
White, non-Hispanic women	570	159	1217	131	1.00
Women of colour, including Hispanic	33	18	59	305	2.36 (1.44 to 3.89)
DSM-IV defined depression at baseline
Never	409	111	880	126	1.00
Past or current	194	66	396	167	1.28 (0.94 to 1.74)
Body mass index (kg/m²)
<20	83	23	177	130	1.04 (0.66 to 1.65)
20–24	332	91	711	128	1.00
25–29	120	35	252	139	1.05 (0.71 to 1.55)
30+	68	28	136	206	1.58 (1.03 to 2.43)
Family history of early natural menopause‡
No	557	155	1194	130	1.00
Yes	46	22	82	268	2.10 (1.32 to 3.34)
Removal of all or part of ovary
No	583	170	1239	137	1.00
Yes	20	7	37	189	1.39 (0.65 to 2.98)
Smoking status
Never	330	100	691	145	1.00
Past	212	54	447	121	0.81 (0.58 to 1.12)
Current	61	23	138	167	1.24 (0.78 to 1.99)
Number of years lived with smoker in home (n=562)
<5	400	103	863	119	1.00
5–15	116	41	233	176	1.41 (0.98 to 2.03)
>15	46	19	97	196	1.49 (0.90 to 2.45)
History of divorce, separation, widowhood
Ever married or partnered
No history divorce, separation, widowhood	384	108	819	132	1.00
History divorce, separation or widowhood	127	39	257	152	1.20 (0.80 to 1.81)
Never married or partnered	92	30	200	150	1.05 (0.73 to 1.52)
Sexual identity
Heterosexual	537	159	1131	141	1.00
Gay, lesbian, or bisexual	66	18	145	124	0.98 (0.60 to 1.62)