Monthly variation in acute appendicitis incidence: A 10-year nationwide population-based study

The present study investigated the monthly variation of acute appendicitis and its association with climatic factors (ambient temperature, relative humidity, atmospheric pressure, rainfall, and hours of sunshine) using a nationwide population-based data set in Taiwan.We identified 237,760 first-time hospitalizations for acute appendicitis from 2000 to 2009. We used the auto-regressive integrated moving average method to examine the monthly variation in the acute appendicitis incidence rates after adjusting for the time-trend effect and seasonality.Throughout the 10-year study period, we found that the monthly incidence rate of acute appendicitis demonstrated a fairly similar monthly pattern for each gender independently and for the pooled data. May through July had the greatest rates, decreasing in August to a trough in February. We used the autoregressive integrated moving average test for seasonality and found a significant difference in the monthly incidence rate for the pooled genders and for the male- and female-only groups (all P0.001). Furthermore, the auto-regressive integrated moving average regression models for the male, female, and combined groups all suggested that a significant positive association exists between the monthly incidence rates of acute appendicitis per 100,000 population and the ambient temperature after adjusting for time trends and month.The results of our study have revealed a significant difference in the monthly incidence rate of acute appendicitis.