An inverse correlation between estimated tuberculosis notification rates and asthma symptoms

Background: A recent ecological analysis demonstrated a strong inverse relationship between tuberculosis notification rates and the prevalence of asthma symptoms in 13-14-year-old children as obtained from the International Study of Asthma and Allergies in Childhood (ISAAC). However, the analysis was confined to the 23 countries in which the tuberculosis notification rates were considered to be of sufficient validity. Methods: A similar analysis was performed using estimated tuberculosis incidence rates obtained from the World Health Organization Global Tuberculosis Programme and asthma symptom prevalence data from ISAAC for both the 6-7 and 13-14 years age groups in 38 and 55 countries, respectively. Results: For the 6-7-year-old children, there was a significant inverse relationship between estimated tuberculosis incidence and the prevalence of key asthma symptoms. However, in the 13-14 year age group, a significant inverse relationship was only demonstrated for 'asthma ever'. Conclusion: The present study extends the inverse relationship between tuberculosis rates and asthma prevalence to the 6-7-year-old age group and suggests that the association, if causal, may be stronger at this younger age.