Age, Period and Cohort Trends in Caries of Permanent Teeth in Four Developed Countries

Objectives. We assessed the relative influences of age, period, and cohort effects on trends in caries experience of permanent teeth in 4 different populations. Methods. We used data from England and Wales, United States, Japan, and Sweden in which numerous cross-sectional, nationally representative surveys have been conducted periodically since the early 1960s. For each country, trends in caries experience (measured by DMFT index-the number of decayed, missing, and filled permanent teeth) were analyzed in an age, period, and cohort (APC) analysis using partial least square regression. Results. A strong effect of age manifested in caries experience, period and cohort effects aside. Caries levels increased through to adolescence; thereafter, there was a larger increase in DMFT in adulthood. Compared with the aging effect, period and cohort effects on caries experience were small. Population DMFT scores decreased over time in all countries except Japan. Cohort effects on caries experience displayed a nonlinear pattern in all 4 countries, with slightly lower caries levels among the oldest and most recent generations. Conclusions. Despite marked recent declines in caries among children, caries levels increase with age and remain problematic in adults.