New Delhi,  April 27:

It’s almost a settled affair that Covid-19 severity and mortality have been higher among men than women patients. A preprint study now holds the clue to the disproportionate impact of coronavirus on the two genders.

According to the researchers from the University of Texas, the Houston Methodist Research Institute and the University of Tennessee Health Science Center, a variety of factors — ranging from the genetic structure of the two sexes to habits determining susceptibility to infection — could be responsible.

HIGHER MALE MORTALITY

In its April 19 weekly surveillance report for Europe, the World Health Organization (WHO) noted that male Covid-19 patients accounted for 63 per cent of all deaths across the continent.

Another report, prepared by the Covid-19 Surveillance Group in March, suggested that of all coronavirus fatalities in Italy, about 29.1 per cent were women.

A new study shows previous epidemics caused by coronavirus cousins also had a higher fatality rate among men than women.

THE LATEST US STUDY

Not yet peer-reviewed, the study by the University of Texas, the Houston Methodist Research Institute and the University of Tennessee Health Science Center compared data from previous epidemics, such as SARS (2002-03) and MERS (2012) to Covid-19’s.

The analysis showed that despite the infection rates being similar, the odd ratio of male mortality remained higher in all three outbreaks.

The retrospective comparison shows that the death rate among men during the SARS outbreak in Hong Kong was 21.9 per cent as opposed to 13.2 per cent among women.

Likewise, an earlier study into MERS showed a mortality rate of 21.2 per cent among men and 15.2 per cent among women.

For Covid-19, the available mortality statistics are not entirely categorised by biological sex in many countries, but the US study estimates that “in terms of mortality, males had increased deaths compared to females from MERS, SARS-CoV,and SARS-CoV2 (Covid-19).”

POSSIBLE EXPLANATIONS

According to the research, one proximate cause could be the sex-specific modulation of the X-linked genes in women, which can influence susceptibility to infection.

The researchers argue that the immune response to coronavirus varies in men and women. “There is statistically significant evidence in these studies strongly hinting at possible sex differences in the immune response.”

A significant number of pre-existing illnesses in men associated with smoking habits and cardiovascular disease could be another factor influencing these results.

In cases related to the MERS outbreak in a Saudi Arabian cohort, researchers suspect that more exposure to the men because of frequent travel and contacts could have been a leading factor.

Another factor, according the researchers, could be handwashing habits. The study notes that “in a 2003 study of 175 individuals indicated that women washed their hands with soap more often than men (61 per cent vs. 37 per cent)”.

The study stresses on the need for further research into the role of “fundamental biological factors that may provide better immune protection for women”.

The research was conducted by Swaminathan P Iyer at the University of Texas, Joe Ensor at Houston Methodist Research Institute and Rudragouda Channappanavar at the University of Tennessee Health Science Center.

COURTESY: India Today