Mother’s Death, Sibling Care and Child Survival in the Past Québec population

1. Mother’s Death, Sibling Careand Child Survival in the Past Québec population A.Gagnon2 , S. Pavard2, B. Desjardins3, E. Heyer2 1 Population Studies Centre, Department of Sociology, University of Western Ontario, Canada 2 UMR 5145 Éco-Anthropologie Equipe « génétique des populations humaines » Musée de l’Homme, France 3 Programme de recherches en démographie historique, Université de Montréal, Montréal, Canada.

2. Rationale for this study • Biodemography • Natural selection at different ages of life, and, in particular, the origins of menopause • Idea: Lost of maternal care (by maternal mortality) decreases the chances for survival of already borne children • In the curse of human evolution, selection for stopping reproduction (when it becomes too dangerous)

3. Difficulty of the study Death of the mother is a relatively rare event  Need many cases to attain statistical significance Few possibilities to make a retrospective study  The most reliable person to be questioned on child survival (the mother) is dead, not available Consequently, very few studies addressed this question Way to overcome these problems: demographic database with longitudinal observation

4. DATA: • Registre de population du Québec ancien (1608-1800), PRDH, Université de Montréal • Contains > 712,000 records (birth, marriage and death certificates) • Approximately 400,000 births available • But, • - Many children retrieved because their survival was clearly affected by confounders (short birth interval, etc.) • In total: 83,229 individual records of live birth (from 1625 to 1759) • Among them, 9,840 children lost their mother before age fifteen (still large sample size) • … makes up for lack of qualitative data…

5. Survival to age 15 according to the survival statusof the mother

6. Odds ratio of dying of motherless children (against children whose mother was alive) : Deaths occurring after mother’s death *p < 0.05 **p < 0.005 ***p < 0.0005 ****p < 0.0001

7. Mother’s death takes place here Deaths occurring before mother’s death Deaths occurring after mother’s death General mortality (mother’s alive) Time

8. Mother’s death takes place here Deaths occurring after mother’s death Deaths occurring before mother’s death Among the deaths occurring after mo-ther’s death, many are due to the fact that mortality is higher in some fa-milies and not to maternal care lack. General mortality level (mother’s alive) Time

9. Mother’s death takes place here Corrected number of deaths: Deaths of children occurring because of mother’s death (lack of maternal care) General mortality (mother’s alive) Time

10. Odd ratios of dying for motherless children corrected for family heterogeneity Age group Mortality (28 days - 5 years) (0/00) : Deaths occurring after mother’s death *p < 0.05 **p < 0.005 ***p < 0.0005 ****p < 0.0001

11. Gender difference in the risk of death for motherless kids?

12. Survival to age 15 per sex according to the survival status of the mother

13. Survival up to age 15 (this includes only those who died)

14. Percentage of increase of mortality related to mother’s death Age group : Deaths occurring after mother’s death *p < 0.05 **p < 0.005 ***p < 0.0005 ****p < 0.0001

15. Two hypotheses • 1) Girls could be more “psychologically” affected by the death of the mother than boys (Child Bereavement Study, Worden, 1996) • 2) Girls took up the responsibility of the missing mother  Entails a higher risk of death by “investing in someone else” or by cross infections

16. Sibling care?

17. Mother ALIVE Boys (27 226 ) Girls (27778 ) Exp (B) Sign. Exp (B) Sign. Mother’s age <25 0.0054 0.1633 25 - 35 1.20 0.0013 1.11 0.0673 >35 1.15 0.0390 1.10 0.1463 Older brothers None 0.1931 0.5544 1 - 2 0.96 0.5647 1.06 0.4135 3 - 5 0.85 0.0631 1.09 0.2998 6 or + 1.17 0.4809 0.83 0.4541 Older sisters None 0.3793 0.1910 1 - 2 0.91 0.2022 1.10 0.1511 3 - 5 1.02 0.8215 0.96 0.6558 6 or + 0.85 0.5887 0.88 0.6921 Proportional hazard regression (or Cox regression) estimates of the odds of dying between age 3 and 15given the number of elderly siblings No significant impact…

18. Mother DECEASED Boys (4 337) Girls (4 357) Exp (B) p Exp (B) P Mother’s age <25 0.9524 0.8702 25 - 35 1.02 0.8761 1.01 0.9022 >35 1.05 0.7557 1.07 0.6249 Older brothers None 0.0044 0.0022 1 - 2 0.40 0.0010 0.45 0.00 20 3 - 5 0.35 0.0004 0.36 0.0002 6 ou + 0.50 0.0948 0.53 0.1270 Older sisters None 0.0047 0.0010 1 - 2 0.40 0.0011 0.43 0.0011 3 - 5 0.39 0.0011 0.35 0.0002 6 ou + 0.22 0.0071 0.19 0.0081 Proportional hazard regression (or Cox regression) estimates of the odds of dying between age 3 and 15given the number of elderly siblings

19. Included variables : B SE Wald ddl p Exp(B) - Age of the mother at birth .032 .007 20.132 1 .000 1.032 - Age of the child at the death of the - .309 .011 721.817 1 .000 .734 mother - Older brothers None 7.427 3 .059 1 – 2 - .072 .087 .688 1 .407 .930 3 – 5 - .278 .112 6.214 1 .013 .757 6 or + - .345 .235 2.158 1 .142 .708 - Older sisters None 13.752 3 .003 1 – 2 - .101 .086 1.376 1 .241 .904 3 – 5 - .332 .113 8.636 1 .003 .718 6 or + - .802 .288 7.771 1 .005 .449 Risks of death for children whose mother died (Cox)

20. Conclusion • Mother’s death and child survival: • The younger was the child when losing his/her mother, the higher was the risk • But significantly diminished chances for survival over all childhood • Sex differentials and “sibling care”: • Boys generally had a higher mortality • They died sooner than girls (endogenous causes) • But girls seemed to be more affected by mother’s death (two hypotheses) • Older sisters appeared to offer a “protector effect”

21. End