Table 2.
Cox Proportional Hazard Ratios (HRs) of Mortality Because of Cardiovascular Disease and Cancer According to Age at First Birth, the Ohsaki Cohort, Japan, 1995–2008
| Age at first birth (years) | ||||
|---|---|---|---|---|
| ≤19 | 20–24 | 25–29 | ≥30 | |
| (n = 498) | (n = 13,607) | (n = 5,625) | (n = 894) | |
| Person-years | 5,347 | 153,247 | 64,446 | 9,881 |
| All-cause | ||||
| No. of deaths | 76 | 1352 | 617 | 120 |
| Crude HR (95% CI) | 1.62 (1.29–2.04) | 1.00 (referent) | 1.08 (0.99–1.19) | 1.38 (1.15–1.67) |
| p-value | <0.01 | 0.10 | <0.01 | |
| Age at baseline adjusted HR (95% CI) | 1.35 (1.07–1.70) | 1.00 (referent) | 1.05 (0.95–1.15) | 1.30 (1.08–1.57) |
| p-value | 0.01 | 0.34 | <0.01 | |
| Multivariate HRa (95% CI) | 1.17 (0.92–1.49) | 1.00 (referent) | 1.09 (0.99–1.20) | 1.33 (1.08–1.62) |
| p-value | 0.21 | 0.09 | <0.01 | |
| Cancer | ||||
| No. of deaths | 22 | 381 | 178 | 35 |
| Crude HR (95% CI) | 1.66 (1.08–2.55) | 1.00 (referent) | 1.11 (0.93–1.33) | 1.43 (1.01–2.02) |
| p-value | 0.02 | 0.25 | 0.04 | |
| Age at baseline adjusted HR (95% CI) | 1.50 (0.98–2.31) | 1.00 (referent) | 1.08 (0.90–1.29) | 1.37 (0.97–1.94) |
| p-value | 0.06 | 0.42 | 0.07 | |
| Multivariate HRa (95% CI) | 1.31 (0.83–2.06) | 1.00 (referent) | 1.12 (0.93–1.34) | 1.45 (1.00–2.10) |
| p-value | 0.25 | 0.25 | 0.051 | |
| CVD | ||||
| No. of deaths | 27 | 468 | 195 | 38 |
| Crude HR (95% CI) | 1.66 (1.13–2.45) | 1.00 (referent) | 0.99 (0.84–1.17) | 1.26 (0.91–1.76) |
| p-value | 0.01 | 0.90 | 0.17 | |
| Age at baseline adjusted HR (95% CI) | 1.32 (0.89–1.94) | 1.00 (referent) | 0.96 (0.81–1.14) | 1.19 (0.85–1.65) |
| p-value | 0.17 | 0.64 | 0.31 | |
| Multivariate HRa (95% CI) | 1.11 (0.74–1.67) | 1.00 (referent) | 0.97 (0.81–1.16) | 1.13 (0.77–1.62) |
| p-value | 0.62 | 0.72 | 0.51 | |
| Other | ||||
| No. of deaths | 27 | 503 | 244 | 47 |
| Crude HR (95% CI) | 1.55 (1.05–2.28) | 1.00 (referent) | 1.15 (0.99–1.34) | 1.46 (1.08–1.97) |
| p-value | 0.03 | 0.07 | 0.01 | |
| Age at baseline adjusted HR (95% CI) | 1.25 (0.85–1.83) | 1.00 (referent) | 1.11 (0.96–1.30) | 1.37 (1.01–1.84) |
| p-value | 0.26 | 0.16 | 0.04 | |
| Multivariate HRa (95% CI) | 1.11 (0.74–1.65) | 1.00 (referent) | 1.20 (1.02–1.41) | 1.43 (1.03–1.99) |
| p-value | 0.61 | 0.03 | 0.03 | |
Note. CI confidence interval, CVD cardiovascular disease, HR hazard ratio
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)