Do sons reduce parental mortality?

Abstract

BACKGROUND— Although sons are thought to impose greater physiological costs on mothers than daughters, sons may be advantageous for parental survival in some social contexts. We examined the relationship between the sex composition of offspring and parental survival in contemporary China and Taiwan. Because of the importance of sons for the provision of support to elderly parents in these populations, we hypothesized that sons would have a beneficial effect on parental survival relative to daughters. METHODS— We used data from the Chinese Longitudinal Healthy Longevity Survey (CLHLS) and the Taiwan Longitudinal Study of Aging (TLSA). Our CLHLS sample consisted of 4132 individuals ages 65+ in 2002. Our TLSA sample comprised two cohorts: 3409 persons aged 60+ in 1989 and 2193 persons aged 50–66 in 1996.These cohorts were followed for 3, 18, and 11 years, respectively. We used Cox proportional hazards models to estimate the relationship between the sex composition of offspring and parental mortality. RESULTS— Based on 7 measures of sex composition, we find no protective effect of sons in either China or Taiwan. For example, in the 1989 Taiwan sample, the hazard ratio for maternal mortality associated with having an eldest son is 0.979 (95% CI (0.863, 1.111)). In Taiwan, daughters may have been more beneficial than sons in reducing mortality in recent years. CONCLUSION— We offer several explanations for these findings, including possible benefits associated with emotional and interpersonal forms of support provided by daughters and negative impacts of conflicts arising between parents and resident daughters-in-law.