Age-period-cohort effect on lung cancer mortality in Spain, 1982-2021.

Background: The aim of the study is to provide up-to-date information and evaluate the age-period-cohort effects of age-period cohorts on lung cancer (LC) mortality in Spain for the period 1982 to 2021.

Methods: We analysed deaths by LC and population for the period 1982-2021, available from the Spanish National Institute of Statistics. The LC corresponds to code 162 and codes C33 and C34 of the 9th and 10th editions of the International Classification of Diseases, respectively. Age-period-cohort (A-P-C) modelling was applied to compute the net drift, local drift, longitudinal age curve, and rate ratios (RR) of each period and cohort. A-P-C analysis was performed using the A-P-C Web Tool provided by the National Cancer Institute of the United States.

Results: Estimated relative risk in the male birth cohorts has followed a steady downward trend in all cohorts born since 1922, showing an initial period (1922-1947) of slight decline, followed by a more marked decrease in the cohorts born during the period 1947-1977. In the younger cohorts (1977-1997), the decline appears to have stabilised. In women, a strong cohort effect is observed. In those born after the Spanish Civil War (1936 to 1939), the risk increased until it peaked in the 1960s, after which it started to decrease with the same intensity. Period RR in men decreased from 1987 to 1991 (1.1) to 2017-2021 (0.6), while period RR in women increased during this time (from 0.8 to 1.6).

Conclusions: The cohort effect observed in women born after the Civil War suggests that the onset of the LC epidemic may have been due to a higher prevalence of women smokers in these cohorts. However, the trend observed in the younger cohorts suggests a possible slowing-down in the increase in mortality risk in the following years.