Table 4.

Associations between length of interbirth interval and mortality in 1980–2008 by parity (ORs and 95% CIs from discrete-time hazards models), men and women born during 1935–1968 and aged 40–73 years with two to four children

	Men			Women
Months	Parity 2	Parity 3	Parity 4	Parity 2	Parity 3	Parity 4
Interval 1st–2nd birth
0	1.07 (0.92 to 1.25)	1.14 (0.97 to 1.34)	0.78 (0.59 to 1.04)	1.36** (1.15 to 1.61)	1.00 (0.81 to 1.24)	0.90 (0.64 to 1.27)
0>18	1.19** (1.12 to 1.25)	1.17 **(1.11 to 1.23)	1.11** (1.03 to 1.20)	1.16** (1.08 to 1.24)	1.12**(1.05 to 1.19)	1.10* (1.00 to 1.21)
Interval 2nd–3rd birth†
0		1.07 (0.95 to 1.20)	1.18 (0.97 to 1.44)		1.26**(1.10 to 1.44)	0.97 (0.74 to 1.26)
0>18		1.14** (1.06 to 1.22)	1.12* (1.02 to 1.22)		1.10* (1.00 to 1.20)	1.00 (0.90 to 1.11)
Number of intervals <18 months
0	1	1	1	1	1	1
1	1.17** (1.11 to 1.22)	1.12** (1.08 to 1.16)	1.09**(1.03 to 1.15)	1.18**(1.12 to 1.26)	1.21**(1.12 to 1.30)	1.06 (0.99 to 1.14)
2		1.41**(1.26 to 1.58)	1.18**(1.08 to 1.30)		1.25**(1.16 to 1.35)	1.06 (0.94 to 1.19)
3			1.18 (0.88 to 1.57)			1.17 (0.79 to 1.72)
Average interval length
0–17		1.22* (1.12 to 1.32)	1.19* (1.04 to 1.36)		1.12**(1.01 to 1.24)	1.22**(1.02 to 1.44)
18–29		1.07* (1.02 to 1.12)	1.10**(1.02 to 1.18)		1.06* (1.00 to 1.13)	1.01 (0.92 to 1.10)
30–41		1	1		1	1
42–59		0.94* (0.90 to 0.98)	0.94 (0.88 to 1.01)		0.94* (0.89 to 1.00)	1.00 (0.92 to 1.08)
60–89		0.94* (0.89 to 0.98)	0.89* (0.82 to 0.98)		0.91**(0.86 to 0.97)	0.87* (0.78 to 0.98)
90+		0.76**(0.70 to 0.82)	0.74**(0.64 to 0.87)		0.85**(0.76 to 0.94)	0.44**(0.25 to 0.77)
Deaths	22 112	15 093	6082	14 736	10 015	3981
Person years	5692.9	3676.7	1210.0	5872.1	3879.1	1308.8

Models include age; period; years of education; marital status, age at first birth and change in coparent since preceding birth.

*p<0.05; **p<0.01.

Reference category is 30–41 months.