Older Adults Carry a Growing Share of Untreated Tuberculosis Burden
Across low- and middle-income countries, tuberculosis does not behave like a static adult disease. It rises with age, steadily and across settings, and the gap between who is sick and who is diagnosed widens as people get older.
A systematic review and Bayesian meta-regression analysis of age-stratified prevalence surveys found that bacteriologically confirmed pulmonary TB increased by 30% for every 10-year increase in age. The pattern held across 82 unique surveys, 30 countries, and 4.6 million participants. In the pooled estimates, prevalence climbed from 127 per 100,000 among people aged 15 to 19 years to 796 per 100,000 in the 75-plus group, a 6.4-fold difference. The age gradient was positive in every country represented in the analysis.
The biological logic is familiar even if the policy response has lagged behind it. As adults age, cumulative exposure rises, immune control can weaken, and the likelihood that latent infection progresses to active disease increases. In high-burden settings, older adults also face longer periods of under-detection, which lets untreated disease persist and continue transmission within households and communities.
Prevalence Climbed Steadily, But Not Uniformly Everywhere
The age pattern was not identical in all regions. Age gradients were lower in Africa than in other regions, and the relationship between age and prevalence was flatter for smear-positive TB than for bacteriologically confirmed disease. Countries with HIV prevalence of 5% or more showed flatter age gradients above 40 years of age, a finding that likely reflects the overlap of competing TB risk structures, HIV-related disease patterns, and differences in who survives to older ages.
The investigators also found that age gradients declined slowly over the study period. This points to a changing epidemiologic mix rather than a collapse of the age effect itself. Even as surveys and notification systems evolved over the decades, the central observation persisted: older adults continued to carry more prevalent undiagnosed TB than younger adults.
The oldest age band carried the heaviest burden, and the middle decades were not spared. In practical terms, the curve did not flatten after young adulthood. It kept rising.
Notification Data Point to Missed Cases in Later Life
A separate signal emerged when survey prevalence was compared with routine notification data. Age-stratified notification-to-prevalence ratios declined by 10% for every 10-year increase in age, suggesting that older adults are less likely to be found and reported relative to the amount of disease present in the community.
This mismatch matters because notification data often drive planning, drug procurement, and screening strategy. If older adults are systematically underdiagnosed, then the official burden picture becomes skewed toward younger groups and the service model follows suit. Clinic-based case finding tends to miss the people who present later, cough less conspicuously, or are more likely to have their symptoms attributed to chronic lung disease, frailty, or age itself.
The result is a delay loop. Disease persists longer, diagnosis happens later, and older patients remain both clinically vulnerable and epidemiologically visible for the wrong reasons.
Why Age Should Change TB Program Design
This analysis assembled data from population-based surveys conducted between 1993 and 2025, including national and sub-national studies, and used a pre-registered approach to examine age trends across a broad swath of low- and middle-income countries. The scale of the evidence matters because age patterns in TB have often been inferred from smaller, fragmented datasets or from specific countries and subgroups.
Older adults sit at the intersection of several TB risks. They may have accumulated lifetime exposure to Mycobacterium tuberculosis, live with comorbidities that compromise immune function, or face barriers to seeking care promptly. Screening algorithms that prioritize only the “most active” or “most symptomatic” patients can miss this group, especially when symptoms are nonspecific or mistaken for chronic respiratory illness. The data argue for age-conscious TB strategies that do not stop at the working-age adult population.
In high-burden countries, this has concrete implications for household contact tracing, community screening, and the thresholds used to trigger diagnostic evaluation. When older people are less likely to make it into notification systems despite carrying more disease, passive case detection is not enough.
What the Survey Evidence Does and Does Not Prove
The analysis was broad, but it remains observational and ecological in nature. It quantifies patterns in prevalence and notification ratios; it does not identify a single mechanism responsible for those patterns, and it cannot by itself prove why older adults are underdetected. Survey definitions also varied, with bacteriologically confirmed TB and smear-positive TB not behaving identically across models, and the included countries differed in HIV prevalence, TB epidemiology, and surveillance quality.
Even so, the consistency across 82 surveys is difficult to dismiss. A 30% rise in prevalence for each decade of age is not a marginal shift. It is a structural signal, and it persisted across different analytic approaches and data subsets.
Older adults are not a peripheral TB population. They are part of the center of the epidemic, and the gap between burden and notification widens with age.
What Programs Will Have to Confront Next
TB control programs in low- and middle-income countries will need to decide whether age remains a blind spot or becomes a screening priority. The evidence here supports a model in which older adults are actively considered in prevalence surveys, targeted outreach, and diagnostic pathways rather than assumed to be adequately reached by general adult services.
The study’s strongest message is simple: untreated TB prevalence rises throughout adulthood, while case detection lags behind. For clinicians and public health teams, the practical consequence is a need to look beyond the usual adult age bands when planning detection strategies, especially in settings where delayed diagnosis in older adults can quietly sustain transmission and worsen outcomes.