Respiratory
The impact of early childhood growth trajectories on the subsequent risk of developing tuberculosis disease Alick Sixpence* Alick Sixpence Sixpence Sixpence Sixpence Sixpence Sixpence Sixpence Department of Epidemiology, Boston University School of Public Health, Boston, Massachusetts, USA
Background
Undernutrition, measured through low body mass index, is a well-established risk factor for tuberculosis in adults. Whether undernourished children are also at greater risk of tuberculosis is unknown.
Methods
We followed HIV-uninfected children from birth to age 10 years in the Drakenstein Child Health Study, a South African birth cohort. Anthropometric measurements were collected at birth, 6, 10 and 14 weeks, and at 6, 9 and 12 months. Using WHO child growth standards, we calculated Z-scores for weight-for-age (WAZ), height-for-age (HAZ), body-mass-index-for-age (BMIZ), and weight-for-height (WFHZ). We used group-based trajectory modelling to classify growth trajectory groups for children with >2 measurements. The outcome was time to tuberculosis diagnosis between ages 1 to 10 years. Cox proportional hazards regression models were used to estimate hazard ratios comparing tuberculosis risk between children in differing growth trajectory groups.
Results
Among 940 children included, 12-month trajectories found two distinct groups for each anthropometric measure (Figure), characterized by ‘high’ (healthy growth) and ‘low’ (poor growth) longitudinal patterns. There were 46 tuberculosis events from 1–10 years, an incidence of 617 cases per 100,000 person-years. Children were at increased tuberculosis risk if they were in lower WAZ (HR, 1.94; 95% CI, 1.07 – 3.53) or HAZ (1.48; 0.83 – 2.66) trajectory groups. There was no differential tuberculosis risk in relation to early-life BMIZ and WFHZ growth. There was no modification of risk by sex although we were limited by statistical power. Altering trajectories to the first 14 weeks of life demonstrated broadly similar results.
Conclusion
Early growth deficits in WAZ were strongly associated with increased tuberculosis risk.
