The Seasonal Variation of Multiple Sclerosis in Chile. A Study of Hospitalization Rates (P06.161)

Abstract

Objective: To evaluate the seasonal variation of MS in Chile. Background The etiology of Multiple Sclerosis (MS) is probably determined by the likely interaction between genetic and environmental factors. Design/Methods: We studied hospital discharge G35 category of ICD-10 from 2001 to 2006 in 13 regions of the country. Specific rates were calculated for each season and were standardized to the 2002 Census population. A second analysis divided ing the year in Spring-Summer (SS) and Fall-Winter (FW). The differences were assessed with the two proportion test and ANOVA. Results: 6850 hospital discharges. Average hospitalization rate 0.20 (Confidence interval (CI), 0.13 to 0.27). There were no significant differences between national average rates when all seasons were analized. There were some regional differences. The Metropolitan Regions had the lowest rate in summer 1.24 (CI, 0.97 to 1.51) and the highest rate in Spring 1.49 (CI, 1.20 to 1.79). Regions XII had the highest rates, ranging from 1.94 (CI, -0.24, 4.12) in summer and 4.99 (CI, 1.49, 8.49) in winter. Statistically significant differences were found summer and winter rates in regions I, III and X, and between spring and fall rates in the II, VI, XI and XII regions. The average rates for SS an WF were 2.20 x 100.000 and 2.10, respectively, a statistical significant difference (p = 0.04). Significant differences were also found in the IV and Metropolitan regions (SS 0.89 and FW 2.16, p= 0.003 and a SS 2.64 and FW 2.54, p= 0.04 respectively) Conclusions: There was no clear seasonal trend of hospitalizations for MS in Chile as measured by hospital discharges when we analyzed the data by the four seasons but if analyzed with Spring-Summer and Fall-Winter a statistically significant average, country wide, higher rate of hospital admissions in Spring-Summer was found. Disclosure: Dr. Diaz has nothing to disclose. Dr. Barahona has nothing to disclose. Dr. Antinao has nothing to disclose. Dr. Silva has nothing to disclose. Dr. Parra has nothing to disclose. Dr. Olivares has nothing to disclose. Dr. Guiloff has nothing to disclose.