title: Geographical distribution of reference value of aging people's left ventricular end systolic diameter based on the support vector regression.
abstract: OBJECTIVE
  The aim of this paper is to analyze the geographical distribution of reference value of aging people's left ventricular end systolic diameter (LVDs), and to provide a scientific basis for clinical examination.
  
  
  METHODS
  The study is focus on the relationship between reference value of left ventricular end systolic diameter of aging people and 14 geographical factors, selecting 2495 samples of left ventricular end systolic diameter (LVDs) of aging people in 71 units of China, in which including 1620 men and 875 women. By using the Moran's I index to make sure the relationship between the reference values and spatial geographical factors, extracting 5 geographical factors which have significant correlation with left ventricular end systolic diameter for building the support vector regression, detecting by the method of paired sample t test to make sure the consistency between predicted and measured values, finally, makes the distribution map through the disjunctive kriging interpolation method and fits the three-dimensional trend of normal reference value.
  
  
  RESULTS
  It is found that the correlation between the extracted geographical factors and the reference value of left ventricular end systolic diameter is quite significant, the 5 indexes respectively are latitude, annual mean air temperature, annual mean relative humidity, annual precipitation amount, annual range of air temperature, the predicted values and the observed ones are in good conformity, there is no significant difference at 95% degree of confidence. The overall trend of predicted values increases from west to east, increases first and then decreases from north to south.
  
  
  CONCLUSIONS
  If geographical values are obtained in one region, the reference value of left ventricular end systolic diameter of aging people in this region can be obtained by using the support vector regression model. It could be more scientific to formulate the different distributions on the basis of synthesizing the physiological and the geographical factors.
  
  
  CONCLUSIONS
  -Use Moran's index to analyze the spatial correlation. -Choose support vector machine to build model that overcome complexity of variables. -Test normal distribution of predicted data to guarantee the interpolation results. -Through trend analysis to explain the changes of reference value clearly.
authors: Department of Geography, Tourism and Environment College of Shaanxi Normal University, Xi'an, 710119 Shaanxi, China. Electronic address: hx_125@126.com.
authors: Xiao
authors: X
authors: Han
authors: Department of Geography, Tourism and Environment College of Shaanxi Normal University, Xi'an, 710119 Shaanxi, China. Electronic address: gemiao@snnu.edu.cn.
authors: Miao
authors: M
authors: Ge
authors: Department of Geography, Tourism and Environment College of Shaanxi Normal University, Xi'an, 710119 Shaanxi, China. Electronic address: dongjie@snnu.edu.cn.
authors: Jie
authors: J
authors: Dong
authors: Department of Geography, Tourism and Environment College of Shaanxi Normal University, Xi'an, 710119 Shaanxi, China. Electronic address: 287764826@qq.com.
authors: Ranying
authors: R
authors: Xue
authors: Department of Geography, Tourism and Environment College of Shaanxi Normal University, Xi'an, 710119 Shaanxi, China. Electronic address: 573531602@qq.com.
authors: Zixuan
authors: Z
authors: Wang
authors: Department of Geography, Tourism and Environment College of Shaanxi Normal University, Xi'an, 710119 Shaanxi, China. Electronic address: 154919667@qq.com.
authors: Jinwei
authors: J
authors: He
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002681:China; D002980:Climate; D005260:Female; D005843:Geography; D006801:Humans; D008297:Male; D008875:Middle Aged; D008962:Models, Theoretical; D012016:Reference Values; D012987:Soil; D062206:Spatial Analysis; D060388:Support Vector Machine; D013599:Systole; D016277:Ventricular Function, Left
chemical_list: D012987:Soil
keywords: Disjunctive kriging; Geographical factors; Left ventricular end systolic diameter; Support vector regression; Trend analysis