Evolution of the pH Level over Time in Patients Suffering from Reflux.

The esophagus carries food from the mouth to the stomach. Continuous exposure to the refluxed stomach acid on the esophageal lining causes a burning sensation in the chest or throat known as heartburn. In this study an attempt has been made to investigate the evolution of the pH level over time. In this study we used the Linear Mixed Model to handling the simulated longitudinal data. We built our model considering random intercept and random slope with cubic trend of time reflected by the mean profile and variance structure. We found that all the components of cubic trend of time (hour, hour2 and hour3) are significant at 5% significance level. This also coincide the mean profile in exploratory data analysis, that is, cubic evolution of the pH level over time exists. The study revealed that there is significant evolution of the pH level over cubic time effect exists in the patients.