鈴木 秀人

Abstract Ecological studies have suggested the protective effect of micro-dose lithium in drinking water against suicide, however, the association between body lithium level and suicide is unknown. We aimed to compare body lithium levels between suicide and non-suicide fatalities. This cross-sectional study included 12 suicides and 16 non-suicides who were examined or dissected at the Tokyo Medical Examiner’s Office from March 2018 to June 2021. The aqueous humor lithium concentration was measured twice using inductively coupled plasma mass spectrometry. Analysis of covariance (ANCOVA) was used to compare the lithium concentration between suicides and non-suicides. Mixed-effects model was conducted to account for all lithium concentration data. The aqueous humor lithium concentration did not change after death (t(7) = −0.70, $$\bar v = - 0.02$$, SE = 0.03, 95% CI = [−0.09, 0.05], P = 0.51, Cohen’s d = 0.01). The aqueous humor lithium concentration was lower in suicides (mean 0.50 μg/L (variance s² 0.04)) than in non-suicides (mean 0.9² μg/L (s² 0.07)) (t(26) = 4.47, $$\bar v = 0.42$$, SE = 0.09, 95% CI = [0.22 to 0.61], P < 0.001, Cohen’s d = 1.71). The ANCOVA showed that death by suicide was significantly associated with lower lithium concentration (F(1, 24) = 8.57, P = 0.007), and the effect size was large (η_p² = 0.26). The random intercept model showed a significant effect of suicide on aqueous humor lithium concentration (b = −0.261, SE = 0.102, 95% CI = [−0.471 to −0.051], t(24) = −2.568, P = 0.017). The results of this study demonstrate that even micro-dose lithium is associated with suicide death. Clinical studies are warranted to examine the effects of micro-dose lithium on suicide prevention.

Background Alcohol consumption may be a risk factor for accidental deaths; however, characteristics of alcohol-related deaths are unclear. We investigated characteristics of alcohol-related accidental deaths to facilitate target strategies. Methods In this article, 1060 cases of accidental deaths examined by the Tokyo Medical Examiner’s Office (2015) were divided into two groups: deceased individuals who drank alcohol (alcohol; n = 212) and those who did not (control; n = 848). Age, sex, alcohol consumption patterns, and manners/causes of deaths were compared. Places where individuals in the alcohol group met with an accident, and their blood alcohol concentration was assessed. Results Lower mean age (60.5 vs. 73.7 years) and a higher male ratio (75.9% vs. 58.5%) were observed in the alcohol group. Daily alcohol consumption was more common in the alcohol group (70.8% vs. 13.4%). Falling was the leading cause of death in the alcohol group, but without a significant difference (alcohol: 31.6%, control: 30.4%). Incidence rates of drowning (22.2% vs. 7.9%) and poisoning (11.3% vs. 2.0%) were significantly higher in the alcohol group. The mean blood alcohol concentration was 1.6 mg/mL. Of the total alcohol-related accidents, 60.8% occurred at home. Falling down the stairs was the primary type of falling, and majority of drownings occurred in a bathtub. Conclusion Male habitual drinkers (middle-aged to older adults) should be targeted to prevent alcohol-related accidental deaths. More than 50% of deaths occurred at home and care should be taken when performing daily activities, including using stairs and while bathing.