Male microchimerism and survival among women

Background During pregnancy, woman and fetus exchange small quantities of cells, and their persistence at later times is termed microchimerism. Microchimerism is known to substantially impact on women's later health. This study examined the survival of women according to male microchimerism status. Methods Male microchimerism presence, measured as Y chromosome in peripheral blood samples, was determined in 272 women from the large Danish Diet, Cancer and Health cohort when aged 50-64 years during 1993-97. Women were followed up for cause-specific death in national Danish registers until the end of 2009. Survival was analysed using Cox regression. Results A total of 190 women (70%) were male microchimerism positive. During follow-up 21 women died, of whom 11 (52%) were male microchimerism positive at enrolment and 10 were negative. Of the 21 deaths, 13 (62%) were due to cancer and 5 (24%) were due to cardiovascular disease. Male microchimerism presence was associated with a reduced hazard ratio of all-cause mortality of 0.42 (95% CI 0.17-1.03). The hazard ratio of death from cancer and cardiovascular disease was 0.24 (95% CI 0.08-0.79) and 1.66 (95% CI 0.18-15.48), respectively, among male microchimerism positive compared with negative women. Conclusions Although the biological mechanisms are not precisely known, male microchimerism presence in peripheral blood of women is associated with substantially improved survival in women. The results also indicate that the association with male microchimerism may vary between different causes of death.