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. 2019 Apr 19;16(8):1415.
doi: 10.3390/ijerph16081415.

Association Between Surrounding Greenness and Schizophrenia: A Taiwanese Cohort Study

Hao-Ting Chang  1 , Chih-Da Wu  2 , Wen-Chi Pan  3 , Shih-Chun Candice Lung  4   5   6 , Huey-Jen Su  7
Affiliations

Association Between Surrounding Greenness and Schizophrenia: A Taiwanese Cohort Study

Hao-Ting Chang et al. Int J Environ Res Public Health. .

Abstract

This study aims to investigate the association between surrounding greenness and schizophrenia incidence in Taiwan. Data of 869,484 individuals without a history of schizophrenia were included from the Longitudinal Health Insurance Database from 2000 through 2010 for analysis. The diagnoses of schizophrenia were based on ICD-9 codes. Greenness exposure was assessed using the satellite-based normalized difference vegetation index, assuming individuals lived near the hospital they most often visited for common cold during the study period. Cox proportional hazards models were applied to assess the association between greenness exposure and schizophrenia incidence after adjustments were made for the potential confounders. A total of 5,069 schizophrenia cases were newly diagnosed during the study period. A negative significant (P < 0.05) association found using 2,000-m buffer distances (distance of a moderately paced 20-min walk) in the whole Taiwan island, cities, and metropolitan areas. The results of the stratified analysis based on sex and health insurance rate suggested surrounding greenness has approximately equal effects of reducing the risk of schizophrenia, regardless of sex or financial status. In conclusion, our findings suggest that more surrounding greenness may reduce the risk of schizophrenia.

Keywords: cohort study; greenness; incidence; normalized difference vegetation index; schizophrenia.

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Conflict of interest statement

The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results

Figures

Figure 1
Figure 1
Databases displayed in the location of Taiwan. (a) The spatial variability of greenness within the whole island based on the MODIS NDVI (Normalized Difference Vegetation Index) image of 2000. (b) The township scale of population density (c) The township scale of incidence rate from 2000 to 2010. (d) The location of mental related hospitals in Taiwan.
Figure 2
Figure 2
Stratified analysis for the hazard ratio of NDVI (estimates with 95% confidence interval) according to sex and health insurance rate less (poorer) than NTD 20,000 and health insurance rate greater than NTD 20,000 (richer). Significance level: * indicates p value < 0.05, ** indicates p value < 0.01, and *** indicates p value < 0.001.
See this image and copyright information in PMC

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