Study On Association Between Normalized Difference Vegetation Index And Brain Gray Matter Volume In Normal Young Adults

Objective: Since the 19 th century,the idea that green land is good for health has become a generally accepted view.Previous studies have shown that environmental factors(such as green space)can affect human brain structure and function.Economic culture,natural environment and other factors can affect human brain gray matter volume,but the relationship between vegetation coverage and human brain gray matter volume has not been established.The purpose of this study is to investigate whether vegetation cover affects the brain gray matter volume of normal young people,and then explore whether air pollution plays an intermediary effect.Methods: In this study,3180 normal young people of Chinese Han nationality were subjected to brain structure magnetic resonance imaging(MRI),and the gray matter of whole brain voxels was calculated by voxel-based morphometry(VBM)Volume(gray matter volume,GMV).Using the geographic information questionnaire to collect the basic personal information of the subject and the annual change of residence since birth,as well as the precise latitude and longitude coordinate information of the corresponding address,on the Google earth engine(GEE)platform,we extract Annual vegetation coverage in 2017: taking the provided latitude and longitude coordinates as the center,calculate the annual average normalized vegetation index(NDVI)within a radius of 1km.In addition,the PM2.5(Particulate Matter 2.5)data in this time range is obtained based on the Socioeconomic Data and Applications Center(SEDAC).Then,based on the longitudinal position information provided by the subject,the arithmetic average of the NDVI and PM2.5 of the subject every year is calculated,and this is taken as the average NDVI and the average PM2.5,respectively.The VBM8 software was used to calculate the gray matter volume of whole brain voxels,and the correlation analysis between voxel-based GMV and NDVI was performed.At the same time,age,gender,educational years and intracranial gray matter volume were used as covariates,and the FWE method was used Compared with correction,test significance P <0.05 was considered statistically significant.The clumps significantly related to average NDVI are defined as regions of interest(ROI),and REST software is used to extract the GMV value in each ROI.Through the bivariate correlation analysis in SPSS 19,the correlation between NDVI and PM2.5 was analyzed,and the statistical result was significant with P <0.01.Using NDVI as the independent variable,GMV as the dependent variable,and PM2.5 as the intermediary variable,the intermediary effect analysis was conducted to explore whether air quality mediates the effect of vegetation coverage on the human gray matter volume.Results:(1)Voxel-based correlation between whole brain GMV and NDVI There is a significant correlation between NDVI and brain GMV in some age groups,as follows: the average NDVI of 1-2 and 13-18 years old has no significant results with whole brain GMV.The average NDVI of 3-4 years old,5-7 years old and 8-12 years old was negatively correlated with the cerebellum on both sides.A total of 11 AAL brain regions of 19-30 years old had GMV values that were significantly correlated with the average NDVI,and some were negatively correlated,mainly including the following brain regions: right cerebellum,right gyrus,right orbital frontal gyrus,The left upper orbital frontal gyrus,lenticular shell nucleus,insula,and temporal gyrus;some are positively correlated,mainly including the following brain regions: left cerebellum,anterior cingulate,sub-cortical cortex,and thalamus.(2)Correlation between NDVI and PM2.5 5-7 years old(r =-0.154,P <0.01),8-12 years old(r =-0.196,P <0.01),13-18 years old(r =-0.166,P <0.01),19-25 years old(r =-0.223,P <0.01)the average PM2.5 is negatively correlated with the average NDVI of the corresponding age group.(3)Correlation between PM2.5 and GMV There is a significant correlation between PM2.5 and brain GMV in some age groups,as follows: the average NDVI of 1-2 and 3-4 years old has no significant results with whole brain GMV.The average PM2.5 of 5-7 years old is negatively correlated with the inferior frontal gyrus of both sides.The average PM2.5 of 8-12 years old is negatively correlated with the right cerebellum and the left orbital subfrontal gyrus.There are 8 AAL brain regions in 13-18 years old,and the GMV values are significantly correlated with the average PM2.5,and some are negatively correlated,mainly including the following brain regions: bilateral cerebellum,right olfactory cortex,and island cortex;some appear as The positive correlation mainly includes the following brain areas: straight gyrus,middle temporal gyrus,thalamus,and paracentral lobules.The average PM2.5 of 19-30 years old was negatively correlated with bilateral cerebellum and bean-shaped putamen.(4)Mediation Analysis Taking the mean NDVI of 5-7 years old as the independent variable,Gmv as the dependent variable,and the mean PM2.5 of 5-7 years old as the intermediary variable,the results of the intermediary effect analysis based on SPSS 19 are as follows: PM2.5 can significantly mediate the influence of NDVI on Gmv,and the intermediary effect can explain-6.28%.Conclusion: This study found that NDVI is associated with GMV(bilateral cerebellum)of normal Chinese Han young people,and NDVI is negatively correlated with PM2.5.Research results indicate that NDVI may affect human gray matter volume by improving air pollution.