Preti A, Miotto P
Psychiatry Branch, Genneruxi Medical Center, Via Costantinopoli 42, I-09129 Cagliari, Italy.
J Affect Disord. 2001 Aug;65(3):253-61. doi: 10.1016/s0165-0327(00)00232-9.
Recent Italian statistics on suicide distribution by time of day also report data on gender and age of victims, factors which have been shown to influence the seasonal distribution of suicide and which could also affect the influence of biological circadian rhythms on suicidal behaviour. This study aims to identify and evaluate any diurnal variations that may be present in suicide occurrence by age and gender in Italy, considering data from 1994 to 1997.
The null hypothesis that there are no variations in the distribution of suicides by time of day (or over the three major periods of the day: morning, afternoon, evening/night) was tested with the chi2 goodness-of-fit test and with ANOVA.
A clear diurnal variation in the distribution of suicides over time can be observed for both genders, with a peak in the late morning (08:00-11:00 h), and a subsequent decrease to a trough in the night hours. This trend varies with age for both genders: in particular, the age groups 45-64 and 65+ show a clear suicide peak in the morning (08:00-11:00 h), whereas younger people have a peak number of suicides in the late afternoon (16:00-19:00 h). Adults (25-44 years old) show an intermediate trend, with a less pronounced peak between the morning and early afternoon hours. The observed trend is more marked among males; however, the distribution of suicides by time of day is clearly congruent by age between both genders.
Diurnal variation in suicide occurrence by age group may be affected by factors distributed unevenly across age groups. In particular, age distribution of disorders leading to suicidal ideation, and the sensitivity of biological systems of different age groups to environmental cues may affect each group's risk of suicide. Socio-relational factors are also likely to contribute to diurnal variation in suicide risk by age and gender. Children and adolescents can generally be presumed to be at school during the morning, therefore their opportunity for self-harm is restricted to afternoon hours. The elderly, on the other hand, may find themselves alone in the morning, when family and friends spend more time away from home due to daily work activities.
Data are based on time of death and not on presumed time of the suicidal act. For suicides committed by certain methods (e.g., poisoning) there may be a considerable difference between time of act and time of death.
The existence of a temporal window in suicide risk implies an improvement in the surveillance of people at risk of suicide and greater attention to chronobiological factors affecting those suffering from mental disorders leading to suicide ideation.
意大利近期关于自杀按时间分布的统计数据也报告了受害者的性别和年龄数据，这些因素已被证明会影响自杀的季节性分布，并且也可能影响生物昼夜节律对自杀行为的影响。本研究旨在根据1994年至1997年的数据，识别和评估意大利自杀发生率按年龄和性别可能存在的昼夜变化。
采用卡方拟合优度检验和方差分析，对自杀按时间分布（或一天中的三个主要时段：上午、下午、晚上/夜间）不存在差异的零假设进行检验。
男女自杀分布随时间均呈现明显的昼夜变化，上午晚些时候（08:00 - 11:00时）达到峰值，随后在夜间降至低谷。这种趋势在男女中随年龄而变化：特别是，45 - 64岁和65岁以上年龄组在上午（08:00 - 11:00时）出现明显的自杀高峰，而年轻人在下午晚些时候（16:00 - 19:00时）自杀人数最多。成年人（25 - 44岁）呈现中间趋势，在上午和下午早些时候之间有一个不太明显的高峰。观察到的趋势在男性中更为明显；然而，按时间分布的自杀情况在男女的年龄方面明显一致。
按年龄组划分的自杀发生率的昼夜变化可能受到各年龄组分布不均的因素影响。特别是，导致自杀意念的疾病的年龄分布，以及不同年龄组生物系统对环境线索的敏感性，可能会影响每个组的自杀风险。社会关系因素也可能导致按年龄和性别划分的自杀风险的昼夜变化。儿童和青少年通常上午在学校，因此他们自我伤害的机会仅限于下午时段。另一方面，老年人可能上午独自在家，此时家人和朋友因日常工作活动离家时间更长。
数据基于死亡时间而非推测的自杀行为时间。对于某些自杀方式（如中毒），行为时间和死亡时间可能存在相当大的差异。
自杀风险存在时间窗口意味着改善对有自杀风险人群的监测，并更加关注影响患有导致自杀意念的精神障碍患者的生物钟因素。
