No abstract available.
Cohort Effect ; Cohort Studies ; Female ; Humans ; Menarche

This study aims to provide a systematical introduction of age-period-cohort (APC) analysis to South Korean readers who are unfamiliar with this method (we provide an extended version of this study in Korean). As health data in South Korea has substantially accumulated, population-level studies that explore long-term trends of health status and health inequalities and identify macrosocial determinants of the trends are needed. Analyzing long-term trends requires to discern independent effects of age, period, and cohort using APC analysis. Most existing health and aging literature have used cross-sectional or short-term available panel data to identify age or period effects ignoring cohort effects. This under-use of APC analysis may be attributed to the identification (ID) problem caused by the perfect linear dependency across age, period, and cohort. This study explores recently developed three APC models to address the ID problem and adequately estimate the effects of A-P-C: intrinsic estimator-APC models for tabular age by period data; hierarchical cross-classified random effects models for repeated cross-sectional data; and hierarchical APC-growth curve models for accelerated longitudinal panel data. An analytic exemplar for each model was provided. APC analysis may contribute to identifying biological, historical, and socioeconomic determinants in long-term trends of health status and health inequalities as well as examining Korean's aging trajectories and temporal trends of period and cohort effects. For designing effective health policies that improve Korean population's health and reduce health inequalities, it is essential to understand independent effects of the three temporal factors by using the innovative APC models.
Aging ; Cohort Effect* ; Cohort Studies* ; Health Policy ; Korea ; Methods ; Socioeconomic Factors

This study aims to provide a systematical introduction of age-period-cohort (APC) analysis to South Korean readers who are unfamiliar with this method (we provide an extended version of this study in Korean). As health data in South Korea has substantially accumulated, population-level studies that explore long-term trends of health status and health inequalities and identify macrosocial determinants of the trends are needed. Analyzing long-term trends requires to discern independent effects of age, period, and cohort using APC analysis. Most existing health and aging literature have used cross-sectional or short-term available panel data to identify age or period effects ignoring cohort effects. This under-use of APC analysis may be attributed to the identification (ID) problem caused by the perfect linear dependency across age, period, and cohort. This study explores recently developed three APC models to address the ID problem and adequately estimate the effects of A-P-C: intrinsic estimator-APC models for tabular age by period data; hierarchical cross-classified random effects models for repeated cross-sectional data; and hierarchical APC-growth curve models for accelerated longitudinal panel data. An analytic exemplar for each model was provided. APC analysis may contribute to identifying biological, historical, and socioeconomic determinants in long-term trends of health status and health inequalities as well as examining Korean's aging trajectories and temporal trends of period and cohort effects. For designing effective health policies that improve Korean population's health and reduce health inequalities, it is essential to understand independent effects of the three temporal factors by using the innovative APC models.
Aging ; Cohort Effect ; Cohort Studies ; Health Policy ; Korea ; Methods ; Socioeconomic Factors

OBJECTIVES: The purpose of the present study was to estimate the prevalence of metabolic syndrome and to investigate the relation between metabolic syndrome and heart rate variability in a community population. METHODS: The study design was cross-sectional, and 1028 subjects, aged 20~87 years, were recruited. Heart rate variability was measured in the sitting position for five minutes. The recorded data were assessed by time-domain (standard deviation of RR interval) and frequencydomain analysis. All subjects were examined for five components of metabolic syndrome. RESULTS: The prevalence of metabolic syndrome in male and female subjects was 25.9% and 27.7%, respectively. The mean value of heart rate variability of the subjects was significantly different between healthy subjects and those with metabolic syndrome. The regression model showed that metabolic syndrome was negatively correlated with heart rate variability. CONCLUSIONS: The results demonstrate that metabolic syndrome has potentially negative effects on the cardiovascular system, and that these effects could be detected by heart rate variability. Follow-up studies able to control the cohort effect are necessary to evaluate the relation between metabolic syndrome and heart rate variability.
Cardiovascular System ; Cohort Effect ; Female ; Heart Rate* ; Heart* ; Humans ; Male ; Prevalence

A recent increase in the number of deaths and mortality rates of breast cancer occurred in Korean women. The increases shows a indirect increase in incidence of breast cancer. The number of deaths from breast cancer and the mortality rate in the future would be of use in the perspectives of breast cancer control and management in Korea. This study is to forecast cancer deaths and age-adjusted death rates in the future(2000-2015 year) by fitting modelling, assuming present trends continue. The number and mortality rate of breast cancer were fitted and estimated by simple linear regression mode. Estimated crude death rates for breast cancer per 100,000 persons were 5 person in 2000, 5.99 person in 2005, 6.98 person in 2010, and 7.79 person en 1015. The observed age-adjusted death rates per 100,000 persons were 1.08 person in 1980, 2.03 person in 1985, 2.49 person in 1990, and 3.29 person in 1995 and the estimated age-adjusted death rates per 100,000 persons were 4.01 person in 2000, 4.72 person in 2005, 5.42 person in 2010, and 6.14 person in 2015. Future estimated increase rate of the number of death is 2 times as many as the estimated rate in population-increase. Particularly noteworthy was an increasing tendency of the age-specific death rate with the ages in death, as like a mortality pattern of breast cancer in western females. These findings suggest that cohort effect might significantly contribute to the increase of the number and mortality of breast cancer in Korean women.
Breast Neoplasms* ; Breast* ; Cohort Effect ; Female ; Humans ; Incidence ; Korea* ; Linear Models ; Mortality*

Breast cancer, the second leading type of cancer in Korean women, has shown increasing incidence over the past 10 years. However, the curves of incidence by age group cast doubt on the birth cohort effect hypothesis. To explain the curves, here I suggest two alternative hypotheses of breast density and viral infection based on pre-existing evidences. Evaluating these hypotheses would require important clues to find unknown risk factors of breast cancer and to plan more effective strategies for breast cancer control in Korean women.
Breast Neoplasms* ; Breast* ; Cohort Effect ; Early Detection of Cancer ; Female ; Humans ; Incidence* ; Mammography ; Papillomaviridae ; Parturition ; Risk Factors

PURPOSE: In spite of gastric cancer's decreasing incidence and mortality rates, it is still the most common cancer in Korea. In the present study, we examined the temporal trends of gastric cancer mortality during the past 20 years in Korea by using an age-period-cohort model, and we predicted the mortality rates for the next 10 years. MATERIALS AND METHODS: Data on the annual number of deaths due to gastric cancer and data on population statistics from 1984 to 2003 were obtained from the Korean National Statistical Office. A log-linear Poisson ageperiod-cohort model was used to estimate age, period and birth cohort effects. To project two periods (10 years) into the future, the new cohort values were estimated by performing linear regression that was applied to a chosen number of the most recent cohort values. RESULTS: The trends of gastric cancer mortality were predominantly explained by the cohort effect; the risk of gastric cancer death decreased since the 1919 birth cohort for both genders. The predicted, expected age-adjusted mortality rates per 100,000 for males and females are 45.72 and 23.75, respectively, during 2004~2008, and 34.62 and 17.93 respectively, during 2009~2013. During 2004~2008 and 2009~2013, the predicted numbers of deaths due to gastric cancer in males are 36,922 and 27,959, respectively, whereas those in females are 19,698 and 14,869, respectively. CONCLUSIONS: Not only the mortality, but also the incidence of gastric cancer in Korea is expected to further decrease in both men and women if the trends of the past 20 years continue.
Cohort Effect ; Cohort Studies ; Female ; Forecasting ; Humans ; Incidence ; Korea* ; Linear Models ; Male ; Mortality* ; Parturition ; Population Characteristics ; Stomach Neoplasms*

PURPOSE: South Korea has the highest incidence rate of thyroid cancer in the world, and the incidence rate continues to increase. The aim of this study was to determine the age-period-cohort effects on the incidence of thyroid cancer in Korea. MATERIALS AND METHODS: Using the Korean National Cancer registry database, age-standardized incidence rates and annual percent changes (APCs) in thyroid cancer according to sex and histologic type were analyzed between 1997 and 2011. Age-period-cohort models were applied using an intrinsic estimator method according to sex. RESULTS: In both men and women, the incidence of thyroid cancer showed a sharp increase from 1997 through 2011. Among the histologic types, papillary carcinoma showed the greatest increase, with APCs of 25.1% (95% confidence interval [CI], 22.7% to 27.5%) in men and 23.7% (95% CI, 21.9% to 25.5%) in women, whereas anaplastic carcinoma did not show a significant increase in either sex. An increase in overall thyroid cancer incidence over time was observed in all birth cohorts. An age-period-cohort model indicated a steeply increasing period effect, which increased prominently from 1997 to 2011 in both men and women. The age effect showed an inverted U-shaped trend. The cohort effect tended to show a slight increase or remain constant from 1952 to 1977, followed by a decrease. CONCLUSION: The period effect can explain the sharp increase in thyroid cancer incidence, strongly suggesting the role of thyroid screening.
Carcinoma ; Carcinoma, Papillary ; Cohort Effect ; Cohort Studies ; Female ; Humans ; Incidence* ; Korea ; Male ; Mass Screening ; Parturition ; Thyroid Gland ; Thyroid Neoplasms*

PURPOSE: Despite the low mortality rate of breast cancer among women in Korea, the breast cancer mortality rate has increased. The aim of this study was to examine trends in breast cancer mortality from 1983 to 2012 in Korea, assessing the importance of age, period, and birth cohort as risk factors. MATERIALS AND METHODS: Data on the annual number of deaths due to female breast cancer and on female population statistics from 1983 to 2012 were obtained from Statistics Korea. A log-linear Poisson age-period-cohort model was used to estimate age, period, and cohort effects. RESULTS: The increasing breast cancer mortality can be explained predominantly by a birth cohort effect: the risk of breast cancer death showed a steady increase until the 1968 birth cohort, and decreased thereafter. There was a sharp increase in the magnitude of the age effect up to 60 years old, then a moderate increase in the effect during the sixties, followed by another sharp increase from 70 years old. The period effect on breast cancer mortality seems negligible based on its adjusted relative risk, even though it was statistically significant after adjusting for age and cohort effects. CONCLUSION: In this study, the mortality pattern of breast cancer in Korea can be explained predominantly by a birth cohort effect. Hence, the overall mortality rate of breast cancer may increase for a while, and show a gradual decrease in the future, which will start from the younger age group.
Breast Neoplasms* ; Breast* ; Cohort Effect ; Cohort Studies ; Female* ; Humans ; Korea* ; Linear Models ; Mortality* ; Parturition ; Population Characteristics ; Risk Factors

PURPOSE: Cancer has been the leading cause of deaths since 1980s in Korea. Among them, colorectal cancer and breast cancer shows steadily increasing pattern, being the fourth and the fifth common site of cancer death in Korea, respectively. This analysis aimed to evaluate potential contribution of birth cohort effects to the recent increases in mortality of colorectal cancer and breast cancer since 1983 in Korea. METHODS: Mortality statistics on deaths of both cancers for the past 20 years of 1983~2002 were obtained from the National Statistical Office. The age-standardized mortality rates were calculated based on the census population of 1992 as a standard. RESULTS: Age-standardized mortality rate for colorectal cancer increased 4.7-fold in men and 3.6-fold in women, whereas 2.1-fold increase in breast cancer mortality during 1983~2002. Age-specific mortality rates for colorectal cancer were steadily increasing by age before 1991 in both genders. However, the mortality rates showed an exponentially increasing pattern for the age group of 70 and over during 1993~2001, which was more prominent in female. The birth cohort curves showed that there were 2- to 3-fold increases in the mortality rates of people who were born in 1931 for colorectal cancer compared to those of people who were born in 1921. Differences in mortality for breast cancer by birth cohort were 1.7-fold among age group of 45~49 and 50~54 between 1936 and 1946. CONCLUSIONS: This analysis suggests that recent increases in mortality of colorectal cancer and breast cancer could potentially be due to birth cohort effects, i.e. rapid changes in life-style in younger generation. The quantitative approach using age-period-cohort model should be pursued.
Breast Neoplasms* ; Breast* ; Cause of Death ; Censuses ; Cohort Effect* ; Cohort Studies* ; Colorectal Neoplasms* ; Female ; Humans ; Korea* ; Male ; Mortality* ; Parturition*