A Novel Approach for Analysis of the Log-Linear Age-Period-Cohort Model: Application to Lung Cancer Incidence

A simple, computationally efficient procedure for analyses of the time period and birth cohort effects on the distribution of the age-specific incidence rates of cancers is proposed. Assuming that cohort effects for neighboring cohorts are almost equal and using the Log-Linear Age-Period-Cohort Model, this procedure allows one to evaluate temporal trends and birth cohort variations of any type of cancer without prior knowledge of the hazard function. This procedure was used to estimate the influence of time period and birth cohort effects on the distribution of the age-specific incidence rates of first primary, microscopically confirmed lung cancer (LC) cases from the SEER9 database. It was shown that since 1975, the time period effect coefficients for men increase up to 1980 and then decrease until 2004. For women, these coefficients increase from 1975 up to 1990 and then remain nearly constant. The LC birth cohort effect coefficients for men and women increase from the cohort of 1890-94 until the cohort of 1925-29, then decrease until the cohort of 1950-54 and then remain almost unchanged. Overall, LC incidence rates, adjusted by period and cohort effects, increase up to the age of about 72-75, turn over, and then fall after the age of 75-78. The peak of the adjusted rates in men is around the age of 77-78, while in women, it is around the age of 72-73. Therefore, these results suggest that the age distribution of the incidence rates in men and women fall at old ages.