A study investigated the nutritional status of tuberculosis (TB)-affected households and evaluated the association between baseline body mass index (BMI), changes in BMI over time, and TB risk, while describing longitudinal BMI trajectories. This was a prospective, noninterventional observational household contact cohort study (ERASE-TB) conducted in Zimbabwe, Mozambique, and Tanzania. Recruitment began between March and September 2021, enrolling household contacts aged 10 years or older of individuals with microbiologically confirmed pulmonary TB. Participants were followed every six months for up to 24 months.
The study included 2,107 household contacts from 822 households (699 in Zimbabwe, 710 in Mozambique, and 698 in Tanzania), with a median follow-up of 23.8 months (IQR, 21.8 to 26.3). At enrollment and follow-up visits, investigators collected sociodemographic data, medical and TB history, and anthropometric measurements including height, weight, and mid-upper arm circumference (MUAC). Participants also underwent blood pressure, hemoglobin, and optional HIV testing. TB screening consisted of the World Health Organization symptom questionnaire and chest radiography, followed by Xpert MTB/RIF Ultra and mycobacterial culture when indicated. An independent endpoint review committee classified TB cases, with confirmed or likely TB used as study outcomes. Prevalent TB was defined as diagnosis at baseline, while incident TB was diagnosed more than 30 days after enrollment. Associations between BMI and TB were assessed using adjusted logistic regression, Cox proportional hazards models, restricted cubic spline analyses, Poisson regression with time-varying BMI changes, and growth mixture modeling to identify latent BMI trajectories.
Among participants, 62.2% were female, the median age was 27 years (IQR, 16 to 42), and 29.5% were adolescents. Underweight was common among adolescents (61.8%) but uncommon among adults (9.2%), whereas 36.6% of adults were overweight or obese. A household-level dual burden of malnutrition, with both underweight and overweight individuals, was observed in 14% to 19% of households across the three countries. Twenty-one participants (1.0%) had prevalent TB and 41 (1.9%) developed incident TB, corresponding to an incidence rate of 13.2 per 1,000 person-years (95% CI, 9.5 to 17.9). Baseline underweight alone was not associated with prevalent TB (adjusted odds ratio [aOR], 0.94; 95% CI, 0.28 to 2.73), but underweight combined with anemia was associated with a substantially higher odds of prevalent TB (aOR, 4.83; 95% CI, 1.03 to 16.8). Similarly, baseline underweight alone was not significantly associated with incident TB (adjusted hazard ratio [aHR], 1.06; 95% CI, 0.49 to 2.26), whereas overweight or obesity showed a nonsignificant trend toward lower risk (aHR, 0.42; 95% CI, 0.15 to 1.16). Underweight combined with anemia was associated with a markedly higher hazard of incident TB (aHR, 3.77; 95% CI, 1.50 to 9.51). Restricted cubic spline analysis demonstrated a nonlinear inverse relationship between BMI and TB risk, with sharply increasing risk below a BMI Z-score of 0. The population attributable fraction for underweight was estimated at 17.3% of incident TB. Among participants who developed incident TB and had repeated anthropometric measurements, 64.7% lost weight during follow-up, and 31.8% of these lost more than 10% of baseline BMI. Adults who developed TB generally started with higher BMI and lost weight before diagnosis, whereas adolescents were often underweight from baseline. Time-varying BMI loss of at least 10% was not significantly associated with incident TB (adjusted incidence rate ratio, 2.27; 95% CI, 0.22 to 22.9), likely reflecting limited statistical power. Growth mixture modeling identified four BMI trajectory groups: decreasing, low stable, high stable, and increasing BMI. Participants in the decreasing BMI trajectory had the highest TB incidence (5.8%) compared with the low stable (1.3%), high stable (0.8%), and increasing (0.0%) groups (P = .005). The decreasing BMI group also had the highest baseline median BMI (30.6 kg/m²).
In this East and Southern African household contact cohort, baseline underweight alone was not independently associated with prevalent or incident TB, but underweight combined with anemia identified individuals at substantially higher risk. Declining BMI over time, particularly among adults who were initially overweight or obese, was associated with subsequent TB development, highlighting the value of longitudinal nutritional monitoring. The observational design limits causal inference, and the relatively small number of TB events reduced statistical precision for some analyses. The findings support integrating repeated nutritional assessment, particularly BMI and anemia evaluation, into TB household contact follow-up programs.
Source: Larsson L, Calderwood CJ, Marambire ET, Held K, Banze D, Mfinanga A, Madziva K, Walsh P, Jacob J, Fernandez FT, Lungu P. Body mass index trajectories and association with tuberculosis risk in a cohort of household contacts in Southern Africa. Clinical Infectious Diseases. 2025 Dec 15;81(6):e600-11.
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