Assessing the effect of restricting access to barbecue charcoal for suicide prevention in New Taipei City, Taiwan: A controlled interrupted time series analysis

Background: Suicides by carbon monoxide poisoning from burning charcoal increased markedly and contributed to a rise in overall suicides in Taiwan in the early 2000s. A previous study indicated short-term effectiveness on reducing suicides of a charcoal restriction programme, which involved voluntary actions from large chain retail stores to move charcoal bags from open shelves to locked cabinets starting from 1st May 2012, in New Taipei City, Taiwan. We investigated the longer-term effect of this programme. Methods: We calculated quarterly age-standardised charcoal-burning and overall suicide rates in New Taipei City and two comparison cities in 2007-2017. Controlled interrupted time-series analysis was used to examine the effect of the charcoal restriction programme. Results: There was no difference between the intervention and comparison cities in step changes in the rates (per 100,000) of charcoal-burning suicide (intervention minus comparison = -0.336, 95% confidence interval -1.173 to 0.502) and overall suicide (-0.270, -1.844 to 1.303) after the intervention, or changes in trends (slopes) in charcoal-burning suicide rates (0.007, -0.055 to 0.069) and overall suicide rates (0.049, -0.138 to 0.236) before and after the intervention. Limitations: There was no legislative requirement to enforce the charcoal restriction. The programme was also restricted to a subset of retail stores. Conclusion: The charcoal restriction programme in New Taipei City showed no effect on reducing charcoal-burning or overall suicides in the five years after its implementation. Future means restriction strategies for suicide prevention should optimise the programme sustainability, ensure the comprehensive means restriction, and monitor the long-term intervention effectiveness.