A time-series analysis on the effects of climate on outpatient visits for psoriasis

Objective Through the relationship between climatic factors such as average temperature, relative humidity, sunshine duration and the number of outpatient visits of psoriasis patients, the influence of climatic factors on the pathogenesis of psoriasis was discussed. Methods We collected daily local outpatient visits' data for psoriasis from The Fifth People's Hospital of Hainan Province in Haikou, Hainan, from January 1 2016 to December 31 2018. Climatic factors, including average temperature, relative humidity, sunshine duration, during the same time were collected from Hainan Meteorological Bureau. Firstly, sequence diagrams were used to observe the average temperature, relative humidity and sunshine duration to determine the stationarity of sequence diagrams. Secondly, through the autocorrelation figure, partial autocorrelation, periodic correlation diagram was used to determine whether there is the correlation, and delay order number. The simple linear regression was carried out to determine the relationship between the various factors. Finally, the summation of time series analysis of the independent variable ARIMAX (Autoregressive Integrated Moving Average with an Independent variable) was used to fit the model and ultimately determine which climatic factors contribute to psoriasis. ARIMAX model parameters are calculated by auto-arima function in R language software. Results Weekly outpatient visits for psoriasis was correlated with the weekly average sunshine duration and the weekly average temperature, but not with humidity. There was a significant correlation between the weekly average temperature and the sunshine duration. The regression equation between them was as follows: Average temperature =183.427 + 0.159 23x duration of sunshine duration ( R 2 =0.512 4, P <0.001). Conclusions Changes in average temperature or sunshine duration can cause changes in the number of outpatient visits for psoriasis patients in Hainan province. These two climatic factors may be the influencing factors for the incidence of psoriasis patients in Hainan Province. 摘要：目的 通过平均气温、相对湿度和日照时长等气候因素与银屑病患者门诊就诊人数之间的联系, 探讨气候 因素对银屑病发病的影响。 方法 收集自2016年1月1日到2018年12月31日海南省第五人民医院银屑病患者门诊 每周的就诊人数。同时收集同一时间的气象资料 , 包括平均气温、相对湿度 、 日照时长等, 所有气候数据均来自海南省 气象局。首先通过时序图观察获知平均气温、相对湿度、日照时长的变化趋势, 初步确定时序图的平稳性, 再通过自相 关图、偏自相关相关图确定是否存在自相关性、周期性、以及延迟阶数, 并通过简单线性回归确定各因素之间的关系, 最后通过时间序列分析中带自变量的求和自回归移动平均模型（Autoregressive Integrated Moving Average with an Independent variable, ARIMAX)来拟合模型, 最终确定哪些气候因素是银屑病发病的影响因素。ARIMAX模型参数通过R 语言软件中的自动定阶auto.arima函数来计算获得。 结果 每周银屑病就诊人数与周平均日照时长和周平均气温之间 存在相关性, 与相对湿度不存相关性;而周平均气温与周日照时长之间存在明显相关性, 两者间回归方程:平均气温= 183.427+0.159 23X周日照时长( R 2 =0.512 4, P <0.001)。 结论 平均气温或日照时长的变化可以引起海南省银屑病患者 门诊就诊人数的变化, 此两项气候因素可能是海南省银屑病患者发病的影响因素。