Investigation of the Pattern of the Effect of Age Group, Time Period, and Birth Cohort on the Incidence of Suicidal Deaths in Lorestan Povince, 2006-2015

Background and Objectives: Suicide is one of the psychosocial problems in Lorestan Province due to its socio-cultural and economic structure. The aim of this study was to investigate the effect of age group, time period, and birth cohort on the suicide incidence in Lorestan Province during the 2006-2015.   Methods: In this study, to overcome the identifiability problem, the Carstensen approach and natural cubic smoothing character were used in age-period-cohort models (APC). Cohort effect was calculated as the relative rate from the 1984 reference cohort for men and 1987 cohort for women. The period effect in both sexes constrained to be relative to 1390 and to be 0 on average with 0 slope. The best APC model for both sexes was the models with "AC-P" parameter, 7 knots, and natural splines for men and B splines for women. All analyses were performed using the R software with Epi package.   Results: The age effect showed that the highest suicide incidence rate was seen in the elderly. Two strong birth cohort effects were observed, one increasing one in the 1980 cohort and one decreasing one in 1991 cohort. The most significant period effect was seen in men in 2011.   Conclusion: The effects of 1991 and 1980 birth cohorts could be due to the consequences of imposed war in Iran. The three economic phenomena, oil price change, increased divorce rate, and increased unemployment rate can be effective in the emergence of the period effect in year 2011.