0036 Population Wakefulness and Nocturnal Suicide Risk

Abstract

Abstract Introduction Nocturnal wakefulness may mediate the relationship between disrupted sleep and suicide risk since nighttime is associated with a peak in negative mood and altered reward processing and executive function. One example is a wakefulness-adjusted nocturnal peak in population suicide risk measured from 2003-2010 (Perlis et al, 2016), but these results have not been replicated with more recent data. Methods A total of 77,784 suicides with known time of fatal injury were extracted from the National Violent Death Reporting System (NVDRS) for 2003-2010 and 2011-2017. These data were then weighted by the estimated proportion of the population that was awake at each hour as derived from the American Time Use Survey (ATUS) for the same years. Suicides were tabulated by clock hours, age, sex, race, and ethnicity, and suicide counts were modeled using robust Poisson regression with hourly population wakefulness entered as an offset term, thus producing hourly incident risk ratios. Results A comparison of analyses between previously reported data (2003 to 2010) and new data (2011 to 2017) showed a consistently elevated risk of suicide at night (midnight to 6AM) that did not differ between time periods. After combining all fifteen years, the maximum number of suicides occurred at noon. Adjusting for population wakefulness, however, revealed a significant increased risk for suicide between 11PM and 5AM, with a 4.61-fold increase at 3AM (IRR: 4.61 [4.11-5.16]). Adjusting for age, sex, race, and ethnicity attenuated, but did not alter these results. In subgroup analyses, the nocturnal risk for suicide was elevated among those with bipolar disorder (5.2% of cases), those with a blood alcohol level greater than 80 mg/dl (14.9% of cases), and those who tested positive for a Z-drug (i.e., zolpidem, zaleplon, and eszopiclone) at autopsy (0.7% of cases). Conclusion Fifteen years of data from suicides across the United States show a significantly increased risk for suicide during the circadian night that peaks at 3AM. Nocturnal wakefulness remains a significant risk factor for suicide, and suicide prevention efforts may benefit from interventions to reduce nocturnal wakefulness and/or an increase in prevention resources at this time. Support (If Any)