Table 2.

HRs and 95% confidence intervals of SH by reproductive factors

Variable	No. of subjects	No. of SH events	Follow-up duration, person-year	Incidence rate, /1,000 person-year	HR (95% confidence intervals)
					Model 1	Model 2	Model 3
Age at menarche, yr
≤12	1,362	53	10,986.6	4.8	0.83 (0.63–1.09)	0.94 (0.71–1.24)
13–14	19,330	901	154,159.2	5.8	1 (Ref)	1 (Ref)
15–16	67,067	3,885	529,316.0	7.3	1.26a (1.17–1.35)	1.09b (1.02–1.17)
≥17	93,504	6,440	732,587.2	8.8	1.50a (1.40–1.61)	1.15a (1.07–1.23)
Age at menopause, yr
<40	3,917	355	29,908.9	11.9	1 (Ref)	1 (Ref)
40–44	11,708	942	90,413.7	10.4	0.88b (0.78–0.99)	0.89b (0.79–1.00)
45–49	46,523	3,074	365,296.6	8.4	0.71a (0.64–0.79)	0.84b (0.75–0.94)
50–54	95,293	5,573	752,279.6	7.4	0.62a (0.56–0.70)	0.78a (0.70–0.87)
≥55	23,822	1,335	189,150.2	7.1	0.60a (0.53–0.67)	0.73a (0.65–0.83)
Reproductive life span, yr
<30	28,130	2,292	217,040.3	10.6	1 (Ref)		1 (Ref)
30–34	74,110	4,996	580,426.7	8.6	0.82a (0.78–0.86)		0.91a (0.86–0.95)
35–39	64,903	3,280	517,309.5	6.3	0.6a (0.57–0.63)		0.80a (0.76–0.84)
≥40	14,120	711	112,272.5	6.3	0.6a (0.55–0.65)		0.74a (0.68–0.81)
Parity
Nulliparity	3,518	163	27,940.8	5.8	1 (Ref)	1 (Ref)	1 (Ref)
1	7,915	360	63,267.0	5.7	0.98 (0.81–1.17)	1.05 (0.87–1.27)	1.05 (0.87–1.27)
≥2	169,830	10,756	1,335,841.2	8.1	1.38 (1.18–1.61)	1.06 (0.90–1.26)	1.06 (0.90–1.26)
Duration of breastfeeding, mo
Never	9,079	406	72,648.3	5.6	1 (Ref)	1 (Ref)	1 (Ref)
<6	7,408	285	59,689.5	4.8	0.85 (0.73–0.99)	0.86 (0.73–1.00)	0.86 (0.73–1.00)
6–11	24,786	1,272	197,014.4	6.5	1.16 (1.03–1.29)	0.97 (0.86–1.09)	0.97 (0.86–1.10)
≥12	139,990	9,316	1,097,696.8	8.5	1.52 (1.37–1.68)	1.00 (0.90–1.12)	1.00 (0.90–1.12)
Duration of HRT, yr
Never	159,628	10,490	1,250,819.9	8.4	1 (Ref)	1 (Ref)	1 (Ref)
<2	12,764	454	104,141.8	4.4	0.52a (0.47–0.57)	0.76a (0.69–0.83)	0.76a (0.69–0.83)
2–4	4,819	174	39,103.8	4.5	0.53a (0.46–0.62)	0.79b (0.68–0.92)	0.79b (0.68–0.92)
≥5	4,052	161	32,983.5	4.9	0.58a (0.50–0.68)	0.78b (0.67–0.91)	0.78b (0.67–0.92)
Duration of OC use, yr
Never	150,657	9,611	1,182,741.3	8.1	1 (Ref)	1 (Ref)	1 (Ref)
<1	17,012	875	136,097.6	6.4	0.79 (0.74–0.85)	0.94 (0.88–1.01)	0.94 (0.88–1.01)
≥1	13,594	793	108,210.1	7.3	0.90 (0.84–0.97)	1.02 (0.94–1.09)	1.02 (0.95–1.10)

Model 1: non-adjusted; Model 2: adjusted for age at menarche, age at menopause, number of parities, duration of breastfeeding, duration of HRT, duration of oral contraceptive use, alcohol consumption, smoking, regular exercise, income, body mass index, hypertension, dyslipidemia, use of three or more oral hypoglycemic agents, insulin treatment, use of insulin secretagogues such as sulfonylureas and glinides; Model 3: adjusted for reproductive life span instead of age at menarche and menopause in Model 2.

HR, hazard ratio; SH, severe hypoglycemia; HRT, hormone replacement therapy; OC, oral contraceptive.

^aP<0.0001 compared with reference values,

^bP<0.05 compared with reference values.