LONDON — For years, global health data has shown a striking disparity in tuberculosis cases: men account for nearly two-thirds of all people diagnosed with the bacterial infection worldwide. However, the root cause behind this gender gap has remained a long-standing medical puzzle.
Now, a major multi-country study led by researchers at University College London (UCL) provides a clearer answer. The findings, published in eClinicalMedicine, suggest that men are more likely to develop TB because they face higher exposure to the bacteria throughout their lives—not because their bodies are inherently more susceptible to becoming sick once infected.
Higher Lifetime Exposure Drives the Disparity
To investigate the disparity, researchers analyzed data from more than 22,000 individuals participating in 11 prospective cohort studies across 14 countries in Europe, Africa, Asia, and South America.
The research team evaluated two primary hypotheses: whether men are infected more frequently due to exposure or whether they progress from initial infection to active disease at a higher rate than women.
The results revealed that men were significantly more likely to already test positive for a latent TB infection at the start of the studies, indicating greater cumulative exposure to the bacteria over time. However, when adjusting for baseline infection status, researchers found no significant difference between men and women in their likelihood of progressing to active disease.
"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," said Dr. Yohhei Hamada, co-first author from the UCL Institute for Global Health.
Social Dynamics and Future Interventions
Tuberculosis is caused by Mycobacterium tuberculosis and primarily affects the lungs. It spreads through airborne droplets when an infected person coughs, sneezes, or speaks, especially in crowded or poorly ventilated environments. Common symptoms include a persistent cough, fever, night sweats, unexplained weight loss, and severe fatigue.
The study's authors emphasize that future research must examine the social and environmental dynamics that increase men’s exposure to the infection. Factors such as occupational environments, social gathering spaces, lifestyle behaviors, and barriers to seeking timely healthcare are expected to play a major role.
"We hope that our research will help inform future research into the biological and social mechanisms underlying sex differences in TB," added co-first author Sujen Surenthirarajah.
By identifying exposure as the key driver of the gender disparity, public health experts believe future prevention strategies can be targeted more effectively—focusing on reducing transmission risks in environments where men are most frequently exposed.
