0680 Nocturnal wakefulness and suicide risk in the Australian population

Introduction Temporal patterns for suicide over a 24-hour period have shown mixed results among prior studies. However, analyses of 24-hour temporal patterns for wakeful actions including suicidal behavior, should adjust for expected sleep requirements that inherently skew such activities to conventional wakeful times. This study analysed the time-of-day for suicide cases from the Australian population for the year 2017, adjusting for expected sleep patterns. Identification of time-of-day trends using this methodology may reveal risk factors for suicide and potentially modifiable contributors. Methods The Australian Coronal database was accessed and data for suicide deaths were extracted for the most recent completed year, 2017. Time of suicidal action is frequently unable to be pinpointed and for this analysis an estimation was performed from time last seen alive and time found subsequently using data extracted from police and coronial reports. Time of suicide was allocated to one of four 6-hourly time bins across 24 hours from the mid position of time last seen alive and time found subsequently. Cases were excluded if allocation to a time bin was not able to be confidently determined if time last seen and time found crossed both boundaries for a given time bin. Prevalence of suicide for each time bin was adjusted for the likelihood of being awake for each bin according to sleep-wake norms published in 2020 from a large Australian community survey of 1966 subjects. Observed prevalence of suicide were compared to expected values predicted from likelihood of being awake across each time bin calculated as a standardised incidence ratio (SIR). Results For year 2017 there were 2208 suicides for which 1407 were able to be allocated into one of four 6-hourly time bins. Reasons for exclusion were cases for which allocaton into a time bin was not able to be performed. When adjusted for the likelihood of being awake based from population norms, cases were significantly more likely to enact suicide between the hours of 2301-0500 than predicted (SIR 3.93, P< 0.001). Furthermore, there was a lower-than expected rate of suicide for the time bins, 1101-1700 (SIR 0.86, P=0.002). When subcategories of suicide cases were analsysed, suicide death in asssociation with alcohol consumption demonstrated the strongest for relatoinship to the 2301-0500 time bin (SIR 6.03, P< 0.001). Conclusion Higher than expected rates of suicide overnight associated proposes that nocturnal wakefulness may represent a modifiable risk factor for triggering suicide events. Nocturnal wakefulness may be linked to increased rates of loneliness and depair as well as greater tendency toward impusive actions and behaviors. Impusivity may be compounded by alcohol consumption Our findings offer a potential mechanism for which individuals with insomnia have increased suicidal thoughts and behaviors. Support (If Any) Untied grant provided by Rhinomed LTD