Discussion
This study aimed to estimate the DALYs of BA in infants less than 2 years in Colombia. The burden of disease method analyzes the impact of disease upon populations through a combination of mortality and morbidity measures into a single summary statistic of population health. A global burden of disease study estimated that lower tract respiratory infections account for around 14.1% of DALYs in infants less than 4 years worldwide (7). In our study, more than 400 000 years of life were lost due to AB in Colombia during 2019. This is, to our knowledge, the first estimate of the burden of bronchiolitis in infants under age two years and remarks the weight in relative and absolute terms of this disease in our society. This disease is potentially preventable pathology since it is mostly caused by common respiratory viruses that are preventable with hygiene, or immunization.
Our study obtained a higher rate of DALYs due to BA compared to the rate by all lower respiratory tract infections in Colombia. The national burden of disease study in 2015 estimated by lower respiratory tract infections 9.9 DALYs per 1000 in infants less than 4 years and 3.98 DALYs per 1000 in infants less than 2 years (20). We estimated only for BA 37.51 DALYs / 1000 person-year (95% CI 28.47 – 53.61). These differences are due to different sources of information, as the national burden of disease study used data from national health surveys while we directly examined the records of epidemiological surveillance. The surveillance records have a greater degree of completeness and less probability of information biases since they are mandatory records in Colombia and completed directly by physicians treating the infant. Also, higher estimates of DALYs based on epidemiological surveillance have been seen in paraquat poisoning (21, 22).
Most of DALYs (62 %) were generated by an infant between 1-2 years. This can be explained by a considerable delay in medical consultation in severe cases, respect for younger infants. A similar result was found in a meta-analysis of six studies of RSV-bronchiolitis in Latin America (23). The pooled of case fatality were higher in infant between 0 to 23 month than 0-11 months (1.74 [CI 95%1.20–2.43] vs 0.51 [CI 95% 0.06–2.76]). This evidence could suggest that an infant older than one year there is a considerable delay in medical consultation in severe cases, respect to the younger infant. This hypothesis must be confirmed by prospective studies comparing if there is any difference in time to medical consultation and their outcomes in morbidity and mortality.
Respect to other diseases, AB generates more DALYs than other diseases ”more publicized” like cervical cancer between 45-59 years (1.6 DALYs per 1000 inhabitants), epilepsy between 30-44 years (1 DALYs per 1000 inhabitants) and leukemia in an infant between 5-14 years (1 DALYs per 1000 inhabitants)(20). This differences are important for decision-making processes within the health sector. An accurate estimate of the population’s health status can be used for determining the expected health care use and is vital for prioritizing effective interventions and evaluating their impact (24).
This study has limitations. First, we may have some degree of information bias and underestimation due to the use of data from the national surveillance and notification system (25). However, since 2008, an increase in the reporting of cases to SIVIGILA has been noted (10). To adjust for underestimation, a sensitivity analysis was performed for each of these parameters taking a range of possible values ​​and their distribution. Importantly, the final result of DALYs was not sensitive to the change in values ​​of these probabilities, guaranteeing the robustness of the model. There are no specific ”disability weights” for Bronchiolitis. In this case, we used data reported for lower respiratory infection because in terms of mortality it does not differ from data presented by patients with other viruses in Colombia (13). In the sensitivity analysis, the percentage of change in the total estimate of DALYS did not exceed 25% within the variables analyzed.