Abstract
OBJECTIVE: Suicide rates in Quebec over the second half of the 20th century show a wide range of variation depending on age and time period. However, few studies have verified the presence of a cohort effect affecting trends in Quebec suicide rates. This study is designed to evaluate the potential effects of age, period and cohort (APC) on trends in suicide between 1950 and 2009 in Quebec.
METHOD: For these APC analyses, we used a multiphase approach combining a graphical inspection followed by an analysis that isolates the cohort effect from age and period effects (linear regression of the residuals from a median polish of the rates).
RESULTS: The graphical inspection of trends in rates points to combined effects of age, period and cohort among both men and women. However, the median polish analysis attributes primary importance to period effects, followed by age effects, but also shows weak cohort effects that are significant only among men born between 1950 and 1979.
CONCLUSION: The variation in Quebec suicide rates appears to be primarily a reflection of period, age and, to a lesser degree, birth cohort. Thus, in addition to sex, selection of risk groups should be based more on age and time period than on birth cohort.
Key Words: Quebec, suicide, age-period-cohort, cohort effect, median polish
Résumé
Objectif: Au Québec, le taux de suicide a connu de fortes variations au cours de la seconde moitié du XX siècle, mais très peu d’études ont vérifié la présence d’un effet de cohorte. Cette étude vise à estimer les effets potentiels d’âge, de période ou de cohorte (APC) dans l’évolution des suicides au Québec entre 1950 et 2009.
MÉTHODE: Une approche multiphase combinant une analyse graphique suivie d’une approche statistique permettant d’isoler l’effet de cohorte des effets d’âge et de période a été utilisée pour effectuer ces analyses APC (régression des résidus obtenus par polissage des taux sur médiane).
RÉSULTATS: L’analyse graphique de l’évolution des taux laisse entrevoir des effets combinés d’âge, de période et de cohorte tant chez les hommes que chez les femmes. Toutefois, l’analyse de polissage sur médiane permet d’identifier d’abord des effets de période, puis d’âge et aussi des effets de cohorte faibles, significatifs uniquement chez les hommes nés entre 1950 et 1979.
CONCLUSION: La variation des taux de suicide au Québec serait principalement associée à la période temporelle et l’âge et, dans une moindre mesure, à la cohorte de naissances. En plus du sexe, le choix de groupe à risque devrait davantage reposer sur l’âge et la période temporelle plutôt que la cohorte de naissance.
Mots Clés: Québec, suicide, âge-période-cohorte, effet de cohorte, polissage sur médiane
Footnotes
Conflict of Interest: None to declare.
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