Men’s higher TB burden linked to greater exposure

Men are more likely than women to catch tuberculosis (TB), finds a new study led by UCL (University College London) researchers.

Globally, men account for around two-thirds of people diagnosed with TB but until now, the reasons for this disparity had remained unclear.

For the new study, published in eClinicalMedicine, researchers investigated whether men are more commonly affected by TB because they are more likely to be exposed to infection or because they are biologically more susceptible to developing active TB disease once infected.

The team analyzed more than 22,000 people across 11 prospective cohort studies in 14 countries across Europe, Africa, Asia and South America.

They found that men were more likely than women to already have a TB infection when the study began. This suggests that men had been exposed to the TB bacteria more often over their lifetime.

However, when this was considered, men were not significantly more likely to develop active TB disease than women.

This suggests that the main reason more men have TB is because they are more likely to catch the infection in the first place, rather than because they are more likely to become ill once infected. 

Our findings improve our understanding of why TB disproportionately affects men and suggest that reducing inequalities in TB exposure among men may have a greater impact on narrowing the sex gap in TB burden than interventions focused solely on progression from infection to disease."

Dr. Yohhei Hamada, Co-first author, UCL Institute for Global Health

TB is an infectious disease caused by bacteria that usually affects the lungs, although it can affect other parts of the body.

Common symptoms of active TB include a long-lasting cough, fever, night sweats, weight loss and fatigue.

The disease is usually spread through the air when a person with active TB in their lungs coughs, sneezes, talks or sings. People are generally more likely to catch TB after spending a lot of time in close contact with someone who is infected – especially in crowded or poorly ventilated places.

The team are now calling for future research to focus on understanding why men are exposed to TB more often and how factors such as work, social environments, lifestyle, and access to healthcare contribute to this difference.

Co-first author, Sujen Surenthirarajah (UCL Institute for Global Health) said: "We hope that our research will help inform future research into the biological and social mechanisms underlying sex differences in TB."

Study limitations

Some participant groups included in the study were small and important information on factors such as smoking, alcohol use, and socioeconomic status was not available for everyone.

Study populations were mostly high-risk groups and people who received TB preventive treatment were excluded from the study.