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Key takeaways:
- Early-life TB puts children at risk for impaired lung function and growth at 5 years old.
- With this knowledge, early TB prevention may protect future lung health and growth.
Early-life TB was related to future wheezing, weak lung function and low measures of weight and height at 5 years old, according to study results published in American Journal of Respiratory and Critical Care Medicine.
“These results suggest that following up with children diagnosed with TB after their recovery may have utility to properly ensure they remain healthy and recover fully from their TB diagnosis,” Leonardo Martinez, PhD, MPH, assistant professor of epidemiology at Boston University School of Public Health, told Healio. “Furthermore, these results suggest that prevention of TB in childhood may have long-term implications on child health.”
In a prospective birth cohort study, Martinez and colleagues analyzed 1,068 children from birth to 5 years old to see how early-life TB impacts growth, wheezing and lung function. All included children were born in South Africa.
Researchers tested the children for TB using chest radiography and several induced sputum sample tests.
Following TB development, researchers evaluated children’s growth and lung function with mixed-effects linear regression models, as well as their chances for wheeze with Poisson regression models.
Within a follow-up period of 7.815 child-years, researchers observed 96 cases of TB (1.228 cases per 100.000 person-years; 95% CI, 1.006-1.500) that spanned across different ages at diagnosis: less than 1 year old (43 cases), 1 to 2 years old (20 cases) and older than 2 years old (33 cases). All but one case was pulmonary TB.
At 5 years old, researchers found that this disease was linked to decreased growth parameters that varied based on age at diagnosis. This included decreased length-for-age (-0.4; 95% CI, -0.68 to -0.11) and weight-for-age z scores (-0.3; 95% CI, -0.59 to -0.01) with a diagnosis between 1 and 4 years old and lower weight-for-age (-0.49; 95% CI, -0.82 to -0.16) and BMI (-0.54; 95% CI, -0.83 to -0.25) z scores with a diagnosis at younger than 1 year old
When evaluating lung health, researchers found that 33% of the 455 children who experienced wheezing had recurrent wheezing. The age at which the child developed TB did not change the likelihood for wheeze after recovery because it was high across all ages compared with those with no history of TB (< 6 months old adjusted incidence rate ratio [aIRR] = 2.42; 95% CI, 1.32-4.43; < 12 months aIRR = 1.64; 95% CI, 1.04-2.6; < 24 months aIRR = 1.69; 95% CI, 1.05-2.72; < 36 months aIRR = 2.07; 95% CI, 1.03-4.17).
Researchers noted that the risk for recurrent wheezing showed similar trends.
Compared with children with no early-life TB, those who did contract TB when they were aged 1 to 4 years showed worse lung function at 5 years old, including decreased tidal volume (–9.42 mL; 95% CI, –15.21 mL to – 3.64 mL) and time to peak tidal expiratory flow over total expiratory time (–2.02%; 95%CI, –3.75% to –0.29%).
Researchers also found differences in lung function among those who had TB depending on their age at diagnosis. For those who contracted TB at younger than 1 year old, lower lung function measures were observed as they got older, such as decreased time to peak tidal expiratory flow over total expiratory time (–2.35%; 95% CI, –4.86% to – 0.17%) at 5 years old and increased fractional exhaled nitric oxide (2.88 ppb; 95% CI, 0.57-5.19 ppb) at 2 years old.
Worse time to peak tidal expiratory flow over total expiratory time (–2.73%; 95% CI, –5.45% to –0.01%) at 5 years old was observed in children who contracted TB when they were aged 1 to 4 years. Further, these children showed reduced tidal volume (–9.32 mL; 95% CI, –14.89 mL to –3.75 mL). Martinez told Healio all the above findings were surprising.
“The impacts were not only centered on lung function, which has been studied before in adults, but also on growth in children as well as wheezing,” he said. “These outcomes have not previously been studied in relation to post-TB morbidity and therefore were novel and unexpected.”
Additionally, adjusting for lower respiratory tract infections still resulted in impaired lung function in those who had early-life TB, according to researchers.
More studies in different patient populations are needed to gain a better understanding of the impact early-life TB has on later lung health, Martinez told Healio.
“Data on post-TB morbidity and sequelae are sparse and this is especially true for children,” he said. “We need a variety of new data from diverse settings in both adults and children. In addition, how our results (specific to children 5 years and younger) are relevant to children as they grow into adolescence and adulthood is unclear. Do children with growth and lung health deficits due to TB catch-up to their counterparts who do not develop TB in adolescence? Are these impacts long-lasting? Future prospective studies with sufficient statistical power and long-term follow-up will need to investigate these questions.”
For more information:
Leonardo Martinez, PhD, MPH, can be reached at [email protected].
References:
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