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Age, period and cohort trends in oral health status in South Korean adults.

OBJECTIVES
The purpose of this study was to identify the age, period and cohort effects on the changes in oral health status in South Koreans.


METHODS
The age, period and cohort analysis (APC analysis) of the oral health status was conducted using an aggregated age-by-time period table. The age-by-time period table was formulated using data from the Korea National Oral Health Survey (KNOHS) 2000 and 2006, and the Korea National Health and Nutrition Examination Survey (KNHANES) 2010 and 2015. Two oral health outcomes were measured: the number of teeth and Decayed-Missing-Filled Teeth (DMFT) index. Descriptive analysis by graphical representation and partial least square (PLS) regression was used for APC analysis.


RESULTS
Both graphical description and PLS regression showed age and cohort effects in oral health status with the number of teeth decreasing and the DMFT index increasing with age. No period effects were found in either index. The number of teeth increased in the recent birth cohorts. However, the DMFT index showed a reverse J-shaped trend, which worsened in recent birth cohorts. The DMFT index increase in the recent cohort was mainly attributed by an increase in the FT index.


CONCLUSIONS
The effects of age on the number of teeth and caries highlight the importance of oral health in adulthood. The increased caries experience in recent cohorts may indicate the limitations of the current oral health policy. It would be relevant to explore what determinants cause the changes in oral health status. Future oral health policies should address the new directions to reduce the burden of oral diseases.