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Table 5 Cox Proportional Hazard Ratios (HRs) of Mortality Because of Cardiovascular Disease and Cancer According to Age at First Birth, Except for Deaths of Less than 1 Year After Follow-up, the Ohsaki Cohort, Japan, 1995–2008

From: Age at first birth and long-term mortality for mothers: the Ohsaki cohort study

 

Age at first birth (years)

 

≤19

20–24

25–29

≥30

 

(n = 492)

(n = 13,551)

(n = 5,589)

(n = 891)

Person-years

5,345

153,218

64,423

9,880

All-cause

 No. of deaths

70

1,296

581

117

 Crude HR (95% CI)

1.56 (1.23–1.98)

1.00 (referent)

1.06 (0.96–1.17)

1.41 (1.16–1.70)

p-value

<0.01

 

0.22

<0.01

 Age at baseline adjusted HR (95% CI)

1.30 (1.02–1.66)

1.00 (referent)

1.03 (0.93–1.13)

1.33 (1.10–1.60)

p-value

0.03

 

0.59

<0.01

 Multivariate HRa (95% CI)

1.12 (0.87–1.44)

1.00 (referent)

1.07 (0.96–1.18)

1.35 (1.10–1.66)

p-value

0.39

 

0.21

<0.01

Cancer

 No. of deaths

19

363

167

35

 Crude HR (95% CI)

1.51 (0.95–2.39)

1.00 (referent)

1.09 (0.91–1.31)

1.50 (1.06–2.12)

p-value

0.08

 

0.34

0.02

 Age at baseline adjusted HR (95% CI)

1.37 (0.86–2.18)

1.00 (referent)

1.06 (0.88–1.27)

1.44 (1.02–2.04)

p-value

0.18

 

0.55

0.04

 Multivariate HRa (95% CI)

1.17 (0.71–1.90)

1.00 (referent)

1.09 (0.90–1.32)

1.50 (1.04–2.18)

p-value

0.54

 

0.37

0.03

CVD

 No. of deaths

24

444

178

36

 Crude HR (95% CI)

1.56 (1.04–2.35)

1.00 (referent)

0.95 (0.80–1.13)

1.26 (0.90–1.77)

p-value

0.03

 

0.57

0.18

 Age at baseline adjusted HR (95% CI)

1.24 (0.82–1.87)

1.00 (referent)

0.92 (0.78–1.10)

1.19 (0.84–1.67)

p-value

0.30

 

0.37

0.33

 Multivariate HRa (95% CI)

1.03 (0.67–1.59)

1.00 (referent)

0.92 (0.77–1.11)

1.10 (0.76–1.60)

p-value

0.39

 

0.61

0.69

Other

 No. of deaths

27

489

236

46

 Crude HR (95% CI)

1.60 (1.08–2.35)

1.00 (referent)

1.14 (0.98–1.34)

1.47 (1.09–1.99)

p-value

0.02

 

0.09

0.01

 Age at baseline adjusted HR (95% CI)

1.29 (0.87–1.90)

1.00 (referent)

1.11 (0.95–1.29)

1.38 (1.02–1.86)

p-value

0.20

 

0.20

0.04

 Multivariate HRa (95% CI)

1.14 (0.76–1.70)

1.00 (referent)

1.20 (1.02–1.41)

1.49 (1.07–2.07)

p-value

0.52

 

0.03

0.02

  1. Note. CI confidence interval, CVD cardiovascular disease, HR hazard ratio
  2. a The multivariate HR has been adjusted for age at baseline (continuous variable), number of births (1, 2, 3, or ≥4), use of oral contraceptives (yes or no), consumption of green vegetables, carrot or pumpkin, orange (for each food, ≤1–2 times per month, 1–2 times per week, 3–4 times per week, or almost every day), consumption of coffee (<1, 1–2, 3–4, or ≥5 cups per day), smoking status (never, former, or currently smoking), alcohol drinking (never, former, or currently drinking), body mass index at baseline in kg/m2 (<18.5, 18.5–24.9, or ≥25.0), increase in body weight since age 20 years (<10.0 or ≥10.0 kg), walking duration (<1 or ≥1 h per day), sleeping time in hours per day (continuous variable), defecation frequency (≥1 time per day, 1 time per 2–3 days, 1 time per 4–5 days or ≤1 time per 6 days) years of education (<10, 10–12, or ≥13 years), ikigai (yes, uncertain, or no), perceived mental stress (high, moderate, or low), and history of diabetes (yes or no)