Background. Lower Respiratory Tract Infections including pneumonia are the fourth cause of death globally. In Ethiopia, pneumonia is the leading cause of death for children under five. However, so far, only a few studies that used longitudinal design and time dependent covariates determined the significant factors of pneumonia. This study sought to determine whether respiratory rate changes differed for under five-year-old pneumonia patients who had been receiving different treatments over time and whether the change was effected by time dependent and independent covariates.

Methods. A longitudinal study design involving marginal Poisson regression models and conditional Poisson regression models was used. After comparing the two, the final interpretation was made using a conditional Poisson regression model owing to its relative powerfulness.

Results. Four hundred and fifty-three under five pneumonia patients were included, of which 44.37% were female. It is found that, compared to rural children, urban children had an estimated mean respiratory rate decrease of 3%. It is also found that, compared to children whose mother practiced only exclusive breastfeeding in the first six months, children whose mother practiced both breastfed and complementary were more likely to be exposed to pneumonia. The estimated mean respiratory rate of children having asthma was 1.073 times that of children who had diarrhea.

Conclusions. In northwest Ethiopia, weight, residence, previous disease history, breastfeeding and temperature are significant factors of pneumonia among children under five. The effectiveness of treatments was dependent on the number of times children visited the hospital. A significant variation of baseline pneumonia status among under five pneumonia patient children was noted in the hospital.

Keywords: GEE, GLIMM, pneumonia, respiratory rate, under five children