December insolation and ultraviolet B radiation are associated with multiple sclerosis mortality in Poland
Wojciech Cendrowski
Background: The role of environmental factors (EF) determining the occurrence of multiple sclerosis (SM) is the subject of current investigations. Objective: To establish association between duration of insolation along with intensity of ultraviolet B (UVB) radiation and mortality rates for SM in Poland. Method: The study was based on assemblage of 2172 SM persons (M – 878, F – 1294) who died in Poland in the years 2004–2008. Regional previous duration of insolation was measured in hours, intensity of UVB radiation was monitored in minimal erythema dose units (MED), ozone concentration in the ground layer of atmosphere was recorded in μg/m3. Measurements of insolation, UVB radiation and ozone concentration were performed at provincial stations and territorial sites of the State Environmental Monitoring. EF were correlated to provincial crude mortality rates (CMR) for MS. Correlational test by Pearson was used in the study. Demographic data were obtained from the Central Statistical Office, information on EF was received from the Institute of Meteorology and the Institute of Environmental Protection. Results: Annual, average, crude MR for MS per 100,000 inhabitants in Poland was 1.12 (SD 0.14). In northern part it amounted to 1.20 (SD 0.18) and in southern part reached 1.03 (SD 0.11). Significant inverse correlation was found between previous minimal duration of insolation in December and CMR for SM in the country: r = -0.518, p = 0.044. Borderline significance of inverse correlation was established between minimal intensity of UVB radiation in December and crude death rates for SM in Poland: r = -0.478, p = 0.060. CMR for SM in northern Poland was accompanied not only by lower UVB radiation level, but also by slower spring increase and autumn faster decrease of radiation. No significant correlation was ascertained between the ground atmospheric ozone concentration or the annual number of days with ozone concentration above 120 μg/m3 and MS mortality rates. Conclusion: Inverse association was found between previous December insolation, UVB radiation level and mortality for SM in Poland. No correlation was ascertained between mortality and the part ozone concentration in the ground layer of the atmosphere.