Suicide Trend and Nowcasting of Suicide in Hong Kong

We matched all suicide cases reported by media in 2019 with confirmed suicide cases recorded in the Coroner’s Court in the same year. According to gender, age, nature of the location, and suicide method of the cases, machine learning techniques were used to estimate the probability and weight of each case being reported in 2020 and 2021. By doing so, an estimation of the total number of suicide cases per day could be obtained.

The number of suicide cases could be extremely low at times; to minimise its effect on estimation, the average of past 7 days’ estimates is used to work out the estimate of the present day. The blue line shown in the figure indicates the suicide trend in Hong Kong and the daily estimate of suicide cases (i.e. the “Suicide Risk Index” as an early warning for suicide prevention).

On the other hand, the 365 days average estimate line and the three levels of upper control limit lines (adding 1, 2, and 3 standard deviations of the estimates to the average) are plotted to indicate the risk level. When the blue line sits above the black / red / yellow / green line, it represents, respectively, a Crisis / Very High / High / Moderate level of suicide risk in the past 7 days; and a low risk when the blue line lies below the green one.