(CNN)In countries where women face more unequal treatment in society, young girls have a lower chance of survival, a new analysis finds.
Gender inequality linked to deaths of girls under 5, new analysis says
Gender inequality is linked to more deaths than expected among girls under the age of 5 compared with boys of the same age, especially in lower- and middle-income countries, says the study, published Tuesday.
Girls have a statistic, perhaps evolutionary, advantage over to boys when it comes to survival. This seems to exist through women's childbearing ages, said lead researcher Valentina Gallo, professor of epidemiology at Queen Mary University of London's Centre for Primary Care and Public Health.
But the study shows that in settings in which sexist attitudes value boys more than girls, this advantage is reduced and a greater proportion of girls are dying, fueled by reduced access to basic health care and more exposure to health risks, such as female genital mutilation. In India, for example, the rates of vaccinating girls are lower than in boys.
The team analyzed gender inequality levels and sex-specific child mortality rates in 195 countries using UNICEF's database of child mortality worldwide and the UN's Gender Inequality Index, which measures gender inequality based on reproductive health, female empowerment and economic status.
"These girls are also further exposed to this risk via their mothers, who may themselves be penalized and valued less than mothers of sons and less able to provide for their daughters," Gallo said.
Using statistical models, the team explored the association between a country's male to female ratio of under-5 child mortality rates -- which shows the probability of deaths per 1,000 live births by sex -- and gender inequality. They found a strong correlation between low levels of equality and more young girls dying than they should, Gallo said.
But other experts warn against claiming causation from such correlations and say more research is needed.
Research has shown that countries with higher infant mortality also experienced more gender discrimination, but this study is the first to examine how this impacts girls and boys separately.
"We are not sure we can generalize these findings. However, at [a] country level, the highest gender inequality led to more girls dying," Gallo said.
Worldwide, more boys are dying than girls, but low to middle-income countries were found to have a smaller difference -- a lower male to female child mortality ratio -- meaning that more girls are dying. This in turn correlated with the countries that had greater gender inequality.
Sarah Hawkes, professor of global public health at University College London and director of the university's Centre for Gender and Global Health, says this advantage has been known since the 17th century.
"The study highlights a few things we have been pushing for in global health research and policies for some time now," said Hawkes, who was not involved in the study.
It is not possible to estimate a natural or ideal rate for the male to female child mortality ratio, Gallo said, but this study found that the ratio varies from 0.8 to 1.4, with a majority of countries having a rate of 1.2, equaling 120 boys dying for every 100 girls.
The higher the gender inequality index, the lower the sex ratio for children under the age of 5 dying. This means that in the world's least-gender-equal societies -- like Yemen, which scored the lowest score out of the 195 countries -- more girls than expected were dying than boys under the age of 5.
India and Tonga are outliers, as their male to female ratio is less than one, so more girls than boys are dying in total, Gallo explained. "There is clearly a problem." Both countries ranked among the lowest for gender equality, with Tonga in the bottom 10.
"It is surprising that [gender inequality] is so strongly associated with mortality. There is something going on that makes girls severely more discriminated than boys in many regions in the world," Gallo said.
The study is a snapshot of gender in the countries examined, but "health statistics 101 will tell you, you can't infer causation from correlations," Hawkes warned. Gallo's team also stressed the need for more research so definitive causal links can be drawn between gender and mortality for under five.
The paper's authors also note that many studies point toward lower-income countries reporting disproportionately fewer female deaths, with families being less likely to record female deaths.