Table 1.

Estimable APC parameters and functions calculated by the Web toola

NomenclatureInterpretation
Net driftAPC analog of the EAPC of the ASR, log-linear component of , , and
CAT = LAT − net driftCross-sectional age trend; log-linear trend in
LAT = CAT + net driftLongitudinal age trend; log-linear trend in
Age deviations, Nonlinear age effects incorporated into , , and ; orthogonal to the linear trend in age
Period deviations, Nonlinear period effects incorporated into and ; orthogonal to the linear trend in period
Cohort deviations, Nonlinear cohort effects incorporated into and ; orthogonal to the linear trend in cohort (over the entire rate matrix)
Fitted temporal trends, Fitted rates in reference age group adjusted for cohort deviations; APC analog of the ASR
Cross-sectional age curve, Fitted cross-sectional age-specific rates in reference period adjusted for cohort deviations
Longitudinal age curve, Fitted longitudinal age-specific rates in reference cohort adjusted for period deviations
Ratio of longitudinal versus cross-sectional age curves Quantifies influence of net drift on age-associated natural history
Period rate ratios, Ratio of age-specific rates in period relative to reference period
Cohort rate ratios, Ratio of age-specific rates in cohort relative to reference cohort
Local drifts, Estimated annual percentage change over time specific to age group
• aFor the APC model defined over age groups and calendar periods with equal intervals. In the Web tool, the central age group, calendar period, and birth cohort define the reference values , respectively. When there is an even number of age, period, or cohort categories, the reference value is the lower of the two central values. In the R package, reference values can be set to any observed age, period, and cohort = period–age in the rate matrix.