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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)