Offspring sex and parental health and mortality

Increased mortality has been observed in mothers and fathers with male offspring but little is known regarding specific diseases. In a register linkage we linked women born 1925-1954 having survived to age 50 (n=661,031) to offspring and fathers (n=691,124). Three approaches were used: 1) number of total boy and girl offspring, 2) sex of the first and second offspring and 3) proportion of boys to total number of offspring. A sub-cohort (n=50,736 mothers, n=44,794 fathers) from survey data was analysed for risk factors. Mothers had increased risk of total and cardiovascular mortality that was consistent across approaches: cardiovascular mortality of 1.07 (95 % CI: 1.03-1.11) per boy (approach 2), 1.04 (1.01-1.07) if the first offspring was a boy, and 1.06 (1.01-1.10) if the first two offspring were boys (approach 3). We found that sex of offspring did not affect total or cardiovascular mortality in fathers. For other diseases or risk factors no robust associations were seen in mothers or fathers. Increased cardiovascular risk in mothers having male offspring suggests a maternal disease specific mechanism. The lack of consistent effects on measured risk factors could suggest other biological pathways than those studied play a role in generating this additional cardiovascular risk.