Sunshine duration and solar radiation contributed to severe Bell’s palsy: An 11-year time series analysis based on a distributed lag non-linear model model

Although previous studies have suggested that meteorological factors are associated with Bell’s palsy, articles on this topic are rare and the results are inconsistent. We aim to reveal the relationship between exposure to different meteorological factors and the onset of severe Bell’s palsy (SBP) with daily data. A case-crossover study based on time-series data was applied, and the minimum risk value of each climatic factor was set as the reference value. We fitted a distributed lag non-linear model (DLNM) which applied quasi-Poisson regression to evaluate the exposure-response association and the lag-response association of meteorological factors on the occurrence of SBP. The mode value and per-decile interval value of each meteorological factor were all included in the analysis. Sensitivity analyses were conducted to test the robustness of results. A total of 863 SBP patients (474 males and 389 females) from 7 hospitals in the Shenzhen Futian District were selected from January 2009 to February 2020. The highest relations effect was tested in the cumulative exposure-response result shown as follows; mean temperature at the minimum value 15.3°C with RR of 10.370 (1.557–69.077) over lag 0 to 13; relative humidity at the 30th value 71% with RR of 8.041 (1.016–63.616) over lag 0 to 14; wind speed at the 90th value 31 (0.1 m/s) with RR of 1.286 (1.038–1.593) over lag 0; mean air pressure at the 30th value 1001.4 (pa) with RR of 9.052 (1.039–78.858) over lag 0 to 5; visibility at the 80th value 26.5 (km) with RR of 1.961 (1.005–1.423) over lag 0 to 2; average total cloud cover at the max value 100 (%) with RR 1.787 (1.014–3.148) over lag 0 to 2; sunshine duration at the 10th value 0.1 (h) with RR of 4.772 (1.018–22.361); daily evaporation shows no relationship in the cumulative result; daily average solar radiation at the minimum value 0 (W/m(2)) with RR of 5.588 (1.184–26.382). There is a relationship between wind speed and the onset of SBP, while mean air pressure, visibility, and average total cloud cover, especially sunshine duration and solar radiation which showed a strong effect, may be associated with severe clinical symptoms of SBP. Mean temperature and relative humidity may affect the course of SBP.