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A nationwide epidemiological study on the associations between ambient particulate matter and suicide in Finland

Nature Mental Health volume 2, pages 426–434 (2024)Cite this article

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Abstract

Growing evidence suggests that air pollution is associated with an increased risk of suicide, albeit with a limited understanding of the mechanisms. Here we examine the short-term association between suicide and particulate matter with a diameter ≤10 µm (PM10) or ≤2.5 µm (PM2.5) using a time-stratified case-crossover design and nationwide data from Finland from 1985 to 2014, including 35,534 suicides, and investigate whether the association differed by demographic, spatial and temporal factors. We observed immediate associations for particulate matter (odds ratio for suicide per 5.64 µg m−3 increase in PM2.5 from the current day (lag0) of 1.010 and 95% confidence interval 1.000–1.020, estimated from single lag models), with a greater magnitude of the associations in the warm season. The associations between exposure to particulate matter and suicide were particularly evident among males, people under 65 years of age and those who died by suicide using violent methods, particularly during the warm season. Our findings help to better understand susceptibility changes and vulnerable subpopulations in the PM–suicide association and improve mental health promotion programs.

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Fig. 1: Spatial distribution of suicide deaths and PM2.5 concentrations at the municipality level in Finland.
Fig. 2: The association between PM2.5 and suicide by lag days and seasons.
Fig. 3: The association between PM2.5 and suicide by subgroups and seasons.
Fig. 4: The association between PM2.5 and suicide by subgroups and subperiod/urbanicity.

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Data availability

The data used in this study cannot be made publicly available. The individual-level suicide data are sensitive health data, and access is strictly limited by Finnish law. Specified people may access it for specified reasons in a specified location using specified computing infrastructure, if a formal application to the Finnish Social and Health Data Permit Authority Findata is successful. Scientists are welcome to contact the last author N.R. for advice or contact Findata directly. Under no circumstances can these data be shared bypassing the national authorities. The air pollution data, based on the global-to-mesoscale dispersion model (SILAM) developed by the FMI, were directly obtained from the FMI as daily data files. The data files provided by the FMI cannot be made publicly available as the data provider only allows them to be shared among a predefined group of users and to be used for specific purposes. However, the SILAM model can be accessed in Github, FMI section at https://github.com/fmidev/silam-model.

Code availability

The R code for the time-stratified case-crossover analysis using a conditional logistic regression is provided in Supplementary Information.

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Acknowledgements

Y.K. was supported by the Japan Society for the Promotion of Science (JSPS) KAKENHI (grant number JP19K17104) and the University of Tokyo Excellent Young Researcher. H.A. was supported by the Strategic Research Council at the Academy of Finland (funding decision numbers 336325 and 336327). H.K. was supported by the Korea Environment Industry and Technology Institute (KEITI) through the ‘Climate Change R&D Project for New Climate Regime’, funded by the Korea Ministry of Environment (MOE; 2022003570006). J.J.K.J. was supported by the Academy of Finland for the project GLORIA (project number 310372).

Author information

Authors and Affiliations

  1. Department of Global Environmental Health, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan

    Yoonhee Kim & Hironobu Watanabe

  2. Geography Research Unit, University of Oulu, Oulu, Finland

    Harri Antikainen

  3. Department of Global Health Policy, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan

    Masahiro Hashizume

  4. School of Tropical Medicine and Global Health, Nagasaki University, Nagasaki, Japan

    Masahiro Hashizume

  5. Graduate School of Public Health, Seoul National University, Seoul, Republic of Korea

    Ho Kim

  6. Center for Environmental and Respiratory Health Research (CERH), Research Unit of Population Health, Faculty of Medicine, University of Oulu, Oulu, Finland

    Jouni J. K. Jaakkola & Niilo Ryti

  7. Biocenter Oulu, University of Oulu, Oulu, Finland

    Jouni J. K. Jaakkola & Niilo Ryti

  8. Medical Research Center Oulu, Oulu University Hospital and University of Oulu, Oulu, Finland

    Jouni J. K. Jaakkola & Niilo Ryti

  9. Finnish Meteorological Institute, Helsinki, Finland

    Jouni J. K. Jaakkola

  10. Department of Public Health, University of Helsinki, Helsinki, Finland

    Niilo Ryti

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Contributions

N.R. acted as the project leader. Y.K. and N.R. initiated and designed the study. Y.K. wrote the first draft of the manuscript. Y.K. and H.W. conducted the statistical analysis. H.A., J.J.K.J. and N.R. provided the suicide and environmental data. M.H., H.K., J.J.K.J. and N.R. provided scientific input in interpreting the results. All authors critically reviewed the manuscript.

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Correspondence to Yoonhee Kim.

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The authors declare no competing interests.

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Nature Mental Health thanks Benedikt Wicki and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Extemded data

Extended Data Fig. 1 Trends of suicide rate and air pollution in Finland.

(a) Annual crude rate of suicide deaths (per 100,000 population) and (b) suicide-weighted average concentrations of PM10, PM2.5, NO2, and SO2 in Finland from 1985 to 2014.

Extended Data Fig. 2 Spatial distribution of PM10, air temperature, and relative humidity at municipality-level in Finland.

(a) Geographical boundaries of the municipalities in Finland based on classifications of year 2020 by four regions combined among special care regions (North & East includes Oulu and Kuopio; West includes Turku and Tampere; South includes Helsinki; Åland) and long-term averages of (b) daily mean PM10, (c) daily mean temperature, and (d) daily mean relative humidity from 1985 to 2014 for each municipality.

Supplementary information

Supplementary Information

Supplementary text regarding codes and Supplementary Tables 1–7 and Figs. 1–8.

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Kim, Y., Antikainen, H., Watanabe, H. et al. A nationwide epidemiological study on the associations between ambient particulate matter and suicide in Finland. Nat. Mental Health 2, 426–434 (2024). https://doi.org/10.1038/s44220-024-00216-2

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