| Outline of Annual Research Achievements |
In the second year of this project, we have updated the daily time-series data of suicide and weather factors. The database now contains 494 locations in 26 countries from 4 to 45 years (please see the list* below). We developed analytical methods to estimate the spatial heterogeneity and temporal changes in the short-term association between ambient temperature and suicide. We first implemented the methods to the Japanese data, including the longest period among the countries from 1972 to 2015 and varying climate conditions across 47 prefectures. The results were in part consistent with those in our previous study focusing on the suicide seasonality based on the multi-country data in terms of the patterns of spatial heterogeneity. In the final year of this project, we will examine the spatial heterogeneity of the temperature-suicide association and the temporal changes for both seasonality of suicide and the association with temperature based on the updated multi-country database.
*List of the 26 countries: Australia, Brazil, Canada, Chile, China, Costa Rica, Czech Republic, Estonia, Ecuador, Finland, Germany, Guatemala, Italy, Japan, Mexico, Paraguay, Philippines, Romania, South Africa, South Korea, Spain, Switzerland, Taiwan, UK, USA, and Vietnam
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
As of the end of FY2020, we have updated our multi-country multi-city data containing daily time series of suicide and weather factors. Specifically, we added newly collected nine countries with 12 locations (Australia, China, Czech Republic, Ecuador, Costa Rica, Guatemala, Paraguay, Finland, and Germany) and two countries with 91 cities in addition to the existing regional level data (Japan and the UK), and extended a study period for South Korea. Therefore, the database now contains 494 locations across 26 countries from 4 to 45 years.
To develop the epidemiological methodologies for estimating short-term spatiotemporal associations between ambient temperature and suicide, we first applied the two-stage meta-regression analysis to the Japanese data across 47 prefectures spanning from 1972 to 2015. We observed that the suicide risks associated with higher temperature were larger for rural prefectures and colder and drier regions, which was in part consistent with the spatial heterogeneity in our previous study focusing on the suicide seasonality using the multi-country data. However, the temporal changes in the temperature-suicide association were unclear and fairly constant over time except for the lessened risks for higher temperature seen in the 2000s.
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| Strategy for Future Research Activity |
In the final year of this project, we will examine the spatial heterogeneity of the temperature-suicide association and the temporal changes for both seasonality of suicide and the association with temperature, using the updated multi-country multi-city database. When investigating the temporal changes, we will select countries where the time-series data was long enough to produce the time-varying effect estimates. Also, a subset of the multi-country database including overlapping years should be used to make the results of the spatial heterogeneity comparable as much as possible.
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