Table 3. Hazard ratios (HRs) with 95% confidence intervals (CIs) for any psychiatric disorder among the surviving twins after co-twin loss at birth, by characteristics of the twin pairs.
| Population-based matched cohort | Twin-sibling family cohort | |||||
|---|---|---|---|---|---|---|
| Number of cases (crude incidence rate, per 1000 person years), exposed twins/unexposed twins | HR (95% CI)* | Number of cases (crude incidence rate, per 1000 person years), exposed twins /matched singletons | HR (95% CI) † | Number of cases (crude incidence rate, per 1000 person years), exposed twins/full siblings | HR (95% CI) £ | |
| By gender of the surviving twins | ||||||
| Male | 103 (13.08)/334 (7.87) | 1.74 (1.37–2.22) | 103 (13.08)/366 (8.61) | 1.63 (1.29–2.07) | 76 (12.96)/64 (7.51) | 2.46 (0.77–7.91) |
| Female | 75 (10.94)/266 (7.61) | 1.37 (1.04–1.81) | 75 (10.94)/357 (10.23) | 1.21 (0.93–1.58) | 54 (11.53)/66 (8.93) | 1.22 (0.25–5.85) |
| By family history of psychiatric disorders | ||||||
| Yes | 20 (17.98)/80 (15.63) | 3.61 (0.43–30.1) | 20 (17.98)/106 (19.17) | 0.79 (0.25–2.56) | 12 (18.00)/16 (12.32) | - |
| No | 158 (11.60)/520 (7.20) | 1.62 (1.33–1.97) | 158 (11.60)/617 (8.58) | 1.44 (1.19–1.74) | 118 (11.94)/114 (7.80) | 1.55 (0.80–3.00) |
| By gender difference of the twin pair | ||||||
| Same-sex twin pair | 130 (12.25)/423 (7.56) | 1.69 (1.34–2.12) | 130 (12.25)/78 (7.97) | 1.78 (1.21–2.63) | 98 (12.70)/93 (7.90) | 1.50 (0.73–3.11) |
| Opposite-sex twin pair | 48 (11.65)/177 (8.27) | 1.30 (0.81–2.10) | 48 (11.65)/38 (9.64) | 1.18 (0.61–2.28) | 32 (11.29)/37 (8.94) | 0.96 (0.29–3.20) |
| By survival days of the deceased twin | ||||||
| 0–6 days | 124 (11.72)/415 (7.58) | 1.57 (1.26–1.94) | 124 (11.72)/516 (9.42) | 1.34 (1.08–1.65) | 91 (12.09)/82 (7.54) | 1.67 (0.70–3.99) |
| 7–27 days | 35 (13.09)/134 (9.21) | 1.35 (0.89–2.05) | 35 (13.09)/142 (9.69) | 1.59 (1.07–2.36) | 26 (13.07)/24 (7.65) | 7.04 (0.79–62.4) |
| 28–59 days | 19 (12.87)/51 (6.33) | 2.56 (1.36–4.81) | 19 (12.87)/65 (8.13) | 1.66 (0.92–2.99) | 13 (12.58)/24 (12.71) | 0.23 (0.03–1.80) |
* Cox regression models were stratified by matching identifiers (sex, birth year, and gestational age), and adjusted for birth weight for gestational age, maternal age at childbirth, low Apgar score (≤7) at 5/10 min, maternal educational level at childbirth, maternal cohabitation status during pregnancy, and family history of psychiatric disorders.
† Cox regression models were stratified by matching identifiers (sex, birth year, gestational age, birth weight for gestational age, birth order), and adjusted for maternal age at childbirth, low Apgar score (≤7) at 5/10 min, maternal educational level at childbirth, maternal cohabitation status during pregnancy, and family history of psychiatric disorders.
£ Cox regression models were stratified by family identifiers, and adjusted for sex, birth year, gestational age, birth weight for gestational age, low Apgar score (≤7) at 5/10 min, maternal educational level at childbirth, and maternal cohabitation status during pregnancy.