in korea , the incidence and mortality rate of invasive cervical cancer have decreased since the introduction of a national cervical cancer screening program . however , it has been suggested that the incidence of cervical cancer among young korean women has increased during the last two decades . furthermore , changes in sexual behavior and the prevalence of human papillomavirus ( hpv ) infection among korean women have also been reported . accordingly , age - period - cohort analysis could help separate the independent effects of age , period and cohort from trends in cancer rates . moreover , period effects reflect the factors that influence all age groups simultaneously , such as implementation of a screening program , while cohort effects reflect changes in lifestyle or external environmental exposures . to the best of our knowledge , only one korean study has examined the trends and age - period - cohort effects on cervical cancer - related mortality , and that study did not evaluate incidence data and used mortality data that are now > 10 years old . therefore , the present study was conducted to describe secular trends in the incidence and mortality rate of cervical cancer in korea , and to use age - period - cohort analysis to evaluate these factors independent effects . data regarding the incidence of cervical cancer between 1993 and 2012 were derived from the korea national cancer incidence database ( kncidb ) of the korea central cancer registry ( kccr ) . the kncidb was launched by the korean ministry of health and welfare in 1980 , and is a nationwide hospital - based cancer registry . the kccr collects data regarding approximately 80%-90% of cancer cases each year from > 180 training hospitals throughout the country . since 1999 , the kccr has covered the entire population under the population - based cancer registry program . the kncidb includes information regarding age , sex , diagnosis date , geographical region , histological type , primary site , and first treatment modality . data regarding cervical cancer - related mortality between 1993 and 2012 were obtained from statistics korea ( http://kosis.kr ) . ethical approval for the research protocol was provided by the institutional review board of the national cancer center , goyang , korea ( ncc2015 - 0185 ) . although the incidence data has high quality and completeness , the majority of mortality data for cervical cancer has been recorded as unspecified uterine cancer deaths . therefore , it is necessary to redistribute unspecified uterine cancer deaths to cervical cancer deaths using a redistribution algorithm estimation of more accurate cervical cancer mortality trends . to accomplish this , we linked the incidence database with the mortality database , then extracted registered cases of malignant neoplasms of the cervix uteri ( c53 ) among deaths from unspecified malignant neoplasms of the uterus ( c55 ) based on the tenth edition of the international classification of diseases . for the present study , we adjusted the numbers of cervical cancer - related deaths ( c53 ) using the proportion of registered cases of cervical cancer ( i.e. , incidence , c53 ) to the number of deaths due to unspecified uterine cancer ( c55 ) in each age group . we excluded the incidence and mortality data from < 20-year - old women because the numbers of cases and cancer - related deaths were very low . the incidence and mortality rates of cervical cancer were grouped into thirteen age groups ( most age groups covered 5 years ; 20 - 24 years old ,  ,  80 years old ) . the incidence and mortality data were also arranged in four 5-year periods from 1993 - 1997 to 2008 - 2012 . the age - standardized incidences and mortality rates were calculated using segi s world standard population . the joinpoint regression analysis program was employed to estimate trends in the age - standardized incidences and mortality rates , and the results were expressed as the annual percent changes ( apcs ) and their 95% confidence intervals ( cis ) for each period . age - period - cohort effects were assessed using a log - linear model to describe trends in the incidence and mortality rate using the intrinsic estimator method . the goodness of fit for each model was estimated using the likelihood ratio test and the akaike information criterion ( aic ) . 12.0 ( statacorp lp , college station , tx ) and joinpoint software ver . 4.1.1 ( surveillance research program , national cancer institute , bethesda , md ) . data regarding the incidence of cervical cancer between 1993 and 2012 were derived from the korea national cancer incidence database ( kncidb ) of the korea central cancer registry ( kccr ) . the kncidb was launched by the korean ministry of health and welfare in 1980 , and is a nationwide hospital - based cancer registry . the kccr collects data regarding approximately 80%-90% of cancer cases each year from > 180 training hospitals throughout the country . since 1999 , the kccr has covered the entire population under the population - based cancer registry program . the kncidb includes information regarding age , sex , diagnosis date , geographical region , histological type , primary site , and first treatment modality . data regarding cervical cancer - related mortality between 1993 and 2012 were obtained from statistics korea ( http://kosis.kr ) . ethical approval for the research protocol was provided by the institutional review board of the national cancer center , goyang , korea ( ncc2015 - 0185 ) . although the incidence data has high quality and completeness , the majority of mortality data for cervical cancer has been recorded as unspecified uterine cancer deaths . therefore , it is necessary to redistribute unspecified uterine cancer deaths to cervical cancer deaths using a redistribution algorithm estimation of more accurate cervical cancer mortality trends . to accomplish this , we linked the incidence database with the mortality database , then extracted registered cases of malignant neoplasms of the cervix uteri ( c53 ) among deaths from unspecified malignant neoplasms of the uterus ( c55 ) based on the tenth edition of the international classification of diseases . for the present study , we adjusted the numbers of cervical cancer - related deaths ( c53 ) using the proportion of registered cases of cervical cancer ( i.e. , incidence , c53 ) to the number of deaths due to unspecified uterine cancer ( c55 ) in each age group . we excluded the incidence and mortality data from < 20-year - old women because the numbers of cases and cancer - related deaths were very low . the incidence and mortality rates of cervical cancer were grouped into thirteen age groups ( most age groups covered 5 years ; 20 - 24 years old ,  ,  80 years old ) . the incidence and mortality data were also arranged in four 5-year periods from 1993 - 1997 to 2008 - 2012 . the age - standardized incidences and mortality rates were calculated using segi s world standard population . the joinpoint regression analysis program was employed to estimate trends in the age - standardized incidences and mortality rates , and the results were expressed as the annual percent changes ( apcs ) and their 95% confidence intervals ( cis ) for each period . age - period - cohort effects were assessed using a log - linear model to describe trends in the incidence and mortality rate using the intrinsic estimator method . the goodness of fit for each model was estimated using the likelihood ratio test and the akaike information criterion ( aic ) . all statistical analyses were performed using the stata software ver . 12.0 ( statacorp lp , college station , tx ) and the age - standardized incidence of cervical cancer among  20-year - old women decreased from 32.8 per 100,000 in 1993 to 15.9 per 100,000 in 2012 ( apc , 3.9% ; 95% ci , 4.2% to 3.6% ) ( table 1 ) . the peak age for the incidence of cervical cancer steadily increased from 60 - 64 years during 1993 - 1997 to 75 - 79 years during 2008 - 2012 ( fig . 1a ) . the age - specific incidence of cervical cancer exhibited a decreasing trend for all age groups , with the exception of women who were < 30 years old and  75 years old ( fig . the incidence of cervical cancer among < 30-year - old women exhibited an increasing trend , and the apc among 20 - 24-year - old women ( apc , 5.6% ; 95% ci , 2.9% to 8.3% ) was greater than that among 25 - 29-year - old women ( apc , 2.5% ; 95% ci , 1.4% to 2.5% ) ( data not shown ) . the age - standardized mortality rate for cervical cancer among  20-year - old women decreased from 5.2 per 100,000 in 1993 to 2.1 per 100,000 in 2012 ( apc , 4.8% ; 95% ci , 5.1% to 4.4% ) ( table 1 ) . 2a , the mortality rate for cervical cancer increased with age , except among elderly people (  70 years old ) during 1993 - 1997 . the age - specific mortality rate for cervical cancer exhibited a decreasing trend for all age groups , with the exception of women who were 20 - 24 years old and  75 years old ( fig . 2b ) . the age - period - cohort model of incidence had the lowest aic value from the goodness of fit tests ( table 2 ) . the age - period - cohort model of mortality had the lowest aic value , and was selected as the model with the best fit based on the goodness of fit test results ( table 2 ) . in the age - period - cohort models , the period effects for the incidence and mortality rate of cervical cancer both decreased from 1993 to 2008 ( fig . the risk ratio for cervical cancer incidence and mortality decreased among women who were born between 1928 and 1973 after we adjusted for age and period effects . however , the risk ratio for cervical cancer incidence and mortality increased among women who were born after 1973 . the age - standardized incidence of cervical cancer among  20-year - old women decreased from 32.8 per 100,000 in 1993 to 15.9 per 100,000 in 2012 ( apc , 3.9% ; 95% ci , 4.2% to 3.6% ) ( table 1 ) . the peak age for the incidence of cervical cancer steadily increased from 60 - 64 years during 1993 - 1997 to 75 - 79 years during 2008 - 2012 ( fig . 1a ) . the age - specific incidence of cervical cancer exhibited a decreasing trend for all age groups , with the exception of women who were < 30 years old and  75 years old ( fig . the incidence of cervical cancer among < 30-year - old women exhibited an increasing trend , and the apc among 20 - 24-year - old women ( apc , 5.6% ; 95% ci , 2.9% to 8.3% ) was greater than that among 25 - 29-year - old women ( apc , 2.5% ; 95% ci , 1.4% to 2.5% ) ( data not shown ) . the age - standardized mortality rate for cervical cancer among  20-year - old women decreased from 5.2 per 100,000 in 1993 to 2.1 per 100,000 in 2012 ( apc , 4.8% ; 95% ci , 5.1% to 4.4% ) ( table 1 ) . 2a , the mortality rate for cervical cancer increased with age , except among elderly people (  70 years old ) during 1993 - 1997 . the age - specific mortality rate for cervical cancer exhibited a decreasing trend for all age groups , with the exception of women who were 20 - 24 years old and  75 years old ( fig . the age - period - cohort model of incidence had the lowest aic value from the goodness of fit tests ( table 2 ) . the age - period - cohort model of mortality had the lowest aic value , and was selected as the model with the best fit based on the goodness of fit test results ( table 2 ) . in the age - period - cohort models , the period effects for the incidence and mortality rate of cervical cancer both decreased from 1993 to 2008 ( fig . the risk ratio for cervical cancer incidence and mortality decreased among women who were born between 1928 and 1973 after we adjusted for age and period effects . however , the risk ratio for cervical cancer incidence and mortality increased among women who were born after 1973 . our findings revealed that the incidence and mortality rate of cervical cancer decreased from 1993 to 2012 . the decreasing trends in the korean incidence and mortality rate are consistent with a pattern of decreasing trends throughout developed countries . our age - period - cohort models also suggest that the decrease in the period and cohort effects significantly contributed to decreases in the incidence and mortality rate of cervical cancer . however , the incidence and mortality rate of cervical cancer gradually increased in the younger birth cohorts , and the recent birth cohort effects ( after the 1973 birth year ) also exhibited an increasing trend . the decreasing cohort effects on the incidence and mortality rate among women who were born from 1928 - 1973 could be explained by improvements in their socioeconomic status , access to hospital - based treatment , and cervical cancer screening program . furthermore , the cohort effect that we observed was similar to that reported in mumbai . in this context , lower socioeconomic status is highly associated with the risk of hpv infection , which is a major risk factor for cervical cancer . thus , the economic growth in korea may have resulted in improved access to hospital - based treatments and greater coverage for the cervical cancer screening program . however , the risk ratio for cervical cancer incidence and mortality exhibited an increasing trend among younger cohorts . there are some possible explanations for the increased cervical cancer incidence and mortality among young women in korea . specifically , sexual behavior in younger cohorts has changed compared with older cohorts and the age at first intercourse has become earlier . these changes in sexual behavior may have led to the increased prevalence of hpv infection in more recent korean birth cohorts . additionally , there have been changes in the nature of cervical cancer in young women . for example , in situ adenocarcinoma or adenocarcinoma has increased among young women in western countries [ 18 - 20 ] . in korea , adenocarcinoma increased from 1993 to 2001 among young women aged 20 - 29 years old . adenocarcinoma is usually located in the cervical canal ; therefore , it was relatively hard to detect in cervical cancer screening compared to squamous cell carcinoma . indeed , it was reported that the proportion of the lymph node metastasis and tumor size have increased among young women aged < 35 years old in korea . finally , young women have a relatively low screening rate for cervical cancer and this rate showed slight decreasing trends among women aged 30 - 39 years old . taken together , these factors have likely contributed to the rise in incidence and mortality of cervical cancer among young women in korea . cervical cancer screening programs are effective and powerful tools that can reduce the risk of cervical cancer and prevent cervical cancer - related deaths . for example , the implementation of cervical cancer screening programs has decreased the incidence and mortality rate of cervical cancer in europe and north america , as well as in asia . based on the age - period - cohort analysis results , period effects imply that this screening has beneficial effects . however , using period effects as a surrogate marker for the screening effects assumes that the cervical cancer screening was implemented at the same time in all age groups . although the korea screening program was implemented in 1996 , not all age groups received free access to the program at the same time . thus , differences in the participation rates may have resulted in the cohorts affecting the cervical cancer incidence and mortality rather than the periods , which were considered a surrogate marker for the screening effects . in addition , our study population represents the entire population of korea and our results are biologically plausible based on the results from other studies . first , the completeness of the incidence data from before 1999 may be lower than that from after 1999 , and this discrepancy may have introduced bias into our estimated trends and age - period - cohort effects . however , the incidence data from after 1993 were collected by the gynecologic oncology committee of korea , which launched a gynecological cancer registry in 1991 , and it is likely that there were very few discrepancies between the data from 1993 - 1998 and the data from 1999 - 2012 . second , the early mortality data are less reliable , and the validity of the cervical cancer - related mortality data would be expected to increase over time . therefore , we adjusted these data by matching the mortality data with the cancer registry data using a redistribution algorithm . nevertheless , it is possible that residual errors were included in the cervical cancer - related mortality data , despite the use of the redistribution algorithm . third , age - period - cohort models always have an internal limitation that is related to identifiability . however , the intrinsic estimator method is a variant of the principal components regression method that provides an unbiased estimation and has a smaller variance than constrained models . the decreasing cohort effects on the incidence and mortality rate among women who were born from 1928 - 1973 could be explained by improvements in their socioeconomic status , access to hospital - based treatment , and cervical cancer screening program . furthermore , the cohort effect that we observed was similar to that reported in mumbai . in this context , lower socioeconomic status is highly associated with the risk of hpv infection , which is a major risk factor for cervical cancer . thus , the economic growth in korea may have resulted in improved access to hospital - based treatments and greater coverage for the cervical cancer screening program . however , the risk ratio for cervical cancer incidence and mortality exhibited an increasing trend among younger cohorts . there are some possible explanations for the increased cervical cancer incidence and mortality among young women in korea . specifically , sexual behavior in younger cohorts has changed compared with older cohorts and the age at first intercourse has become earlier . these changes in sexual behavior may have led to the increased prevalence of hpv infection in more recent korean birth cohorts . additionally , there have been changes in the nature of cervical cancer in young women . for example , in situ adenocarcinoma or adenocarcinoma has increased among young women in western countries [ 18 - 20 ] . in korea , adenocarcinoma increased from 1993 to 2001 among young women aged 20 - 29 years old . adenocarcinoma is usually located in the cervical canal ; therefore , it was relatively hard to detect in cervical cancer screening compared to squamous cell carcinoma . indeed , it was reported that the proportion of the lymph node metastasis and tumor size have increased among young women aged < 35 years old in korea . finally , young women have a relatively low screening rate for cervical cancer and this rate showed slight decreasing trends among women aged 30 - 39 years old . taken together , these factors have likely contributed to the rise in incidence and mortality of cervical cancer among young women in korea . cervical cancer screening programs are effective and powerful tools that can reduce the risk of cervical cancer and prevent cervical cancer - related deaths . for example , the implementation of cervical cancer screening programs has decreased the incidence and mortality rate of cervical cancer in europe and north america , as well as in asia . based on the age - period - cohort analysis results , however , using period effects as a surrogate marker for the screening effects assumes that the cervical cancer screening was implemented at the same time in all age groups . although the korea screening program was implemented in 1996 , not all age groups received free access to the program at the same time . thus , differences in the participation rates may have resulted in the cohorts affecting the cervical cancer incidence and mortality rather than the periods , which were considered a surrogate marker for the screening effects . our results were internally consistent with the incidence and mortality rate of cervical cancer . in addition , our study population represents the entire population of korea and our results are biologically plausible based on the results from other studies . first , the completeness of the incidence data from before 1999 may be lower than that from after 1999 , and this discrepancy may have introduced bias into our estimated trends and age - period - cohort effects . however , the incidence data from after 1993 were collected by the gynecologic oncology committee of korea , which launched a gynecological cancer registry in 1991 , and it is likely that there were very few discrepancies between the data from 1993 - 1998 and the data from 1999 - 2012 . second , the early mortality data are less reliable , and the validity of the cervical cancer - related mortality data would be expected to increase over time . therefore , we adjusted these data by matching the mortality data with the cancer registry data using a redistribution algorithm . nevertheless , it is possible that residual errors were included in the cervical cancer - related mortality data , despite the use of the redistribution algorithm . third , age - period - cohort models always have an internal limitation that is related to identifiability . however , the intrinsic estimator method is a variant of the principal components regression method that provides an unbiased estimation and has a smaller variance than constrained models . the present study revealed that the incidence and mortality rate of cervical cancer in korea have decreased since 1993 . this recent decrease in the incidence and mortality rate of cervical cancer may be due to decreases in the period and cohort effects , which likely reflect the implementation of a korean cancer screening program and changes in lifestyle . however , the risks of cervical cancer incidence and mortality tended to increase in the younger cohorts . these findings suggest that a more effective cervical cancer prevention program is required for younger korean women , such as hpv vaccination , which may be a useful tool for preventing cervical cancer among this population .