A time-series analysis of the daily suicide and ambient air temperature in Astana, Kazakhstan in 2006-2010

Andrej M Grjibovski^1-2, Gulmira Kozhakhmetova³, Aliya Kosbayeva⁴

1. Department of International Public Health, Norwegian Institute of Public Health, Oslo, Norway

2. International School of Public Health, Northern State Medical University, Arkhangelsk, Russia

3. Medical University of Astana, Astana, Kazakhstan

4. WHO office in Kazakhstan, Astana, Kazakhstan

Background: Seasonal variations in the incidence of suicide have been observed in many industrialized countries. Moreover, it is known that the incidence of suicide increases during both economic crises and periods of rapid economic growth. At the same time, the evidence on the associations between air temperature and suicide in rapidly developing settings is scarce.

Aims: To study associations between four different indicators of air temperature and suicide daily cases in Astana – the fast growing capital of Kazakhstan.

Methods: Daily counts of suicides (ICD-10 codes: X60-X84) for the population of Astana, Kazakhstan during 2006-2010 were obtained from the register of “Astana Branch of Forensic Medicine”. Associations between the number of deaths and mean, mean apparent, maximum and maximum apparent temperatures were studied using negative binomial regression models controlling for effects of month, year, weekends and holidays. In addition, we assessed associations between suicide and barometric pressure and humidity.

Results: Altogether, there were 685 suicide cases in Astana during the study period. A clear seasonal pattern with the peak during the spring and summer months was observed. In crude analyses, significant associations between suicide and all temperatures as well as barometric pressure and humidity were observed. After adjustment for potential confounders, only air temperatures remained significantly associated with the outcome. An increase in mean temperature by 1°C was associated with an increase by 1.53% in suicide counts (95% CI: 0.15-2.92). Similar results were obtained for mean apparent temperature (2.01%, 95% CI: 0.39-3.62) and maximum apparent temperature (1.11%, 95% CI: 0.03-2.19).

Conclusions: The results suggest a linear relationship between the temperature and suicide daily cases across the whole spectrum of temperatures with no thresholds in the city of Astana, Kazakhstan. Factors behind this association warrant further research with further going aim to develop mitigation strategies in the period of climate change.