Recent Decrease in Colorectal Cancer Mortality Rate is Affected by Birth Cohort in Korea

Approaches to the problem of nonidentifiability in the age-period-cohort models in the analysis of cancer mortality: a scoping review

Aiming to detect age, period and cohort effects in cancer mortality, age-period-cohort models (APC) can be applied to distinguish these effects. The main difficulty with adjusting an APC model involving age, period and cohort factors is the linear relationship between them, leading to a condition known as the 'nonidentifiability problem'. Many methods have been developed by statisticians to solve it, but there is not a consensus. All these existing methods, with their advantages and disadvantages, create confusion when choosing which one of them should be implemented. In this context, the present scoping review intends not to show all methods developed to avoid the nonidentifiability problem on APC models but to show which of them are, in fact, applied in the literature, especially in the cancer mortality studies. A search strategy was made to identify evidence on MEDLINE (PubMed), Scopus, EMBASE, Science Direct and Web of Science. A total of 46 papers were analyzed. The main methods found were: Holford's method (n = 14; 30%), ntrinsic estimator (n = 10; 22%), Osmond & Gardner method n = 8; 17%), Carstensen (n = 6;13%), Bayesian approach (n = 6;13%) and others (n = 2; 5%). Even with their limitations, all methods have beneficial applications. However, the decision to use one or another method seemed to be more related to an observed geographic pattern.

Prevalence of sexual experience among Korean adolescent: age-period-cohort analysis

OBJECTIVES

Since exposure to sexual content and early sexual initiation among adolescents have become serious social issues in Korea, an in-depth analysis of trends in the prevalence of sexual experience among Korean adolescents is necessary to project the trends and policies required for the next 10 years. The objective of this study was to identify the contributions of age, period, and birth cohort effects on the prevalence of sexual experience in Korean adolescents.

METHODS

We analyzed age-specific, period-specific, and birth cohort–specific trends in the prevalence of sexual experience among 911,502 adolescents (469,593 boys, 51.5%; 441,909 girls, 48.5%) aged 12 years to 17 years from the 2006 to 2017 Korean Youth Risk Behavior Web-based Survey. Joinpoint regression analysis was conducted to examine significant changes in the prevalence of sexual experience and to find the optimal number and location of places where trends changed.

RESULTS

The prevalence of sexual experience generally increased with age in all periods in both boys and girls. In boys, the prevalence of sexual experience increased in recent periods, especially in the age group of 12-13 years, while the prevalence of sexual experience decreased in the age group of 16-17 years. In girls, the age group of 12-13 years showed an increased prevalence of sexual experience in recent periods. However, the prevalence showed a decreasing trend in the age group of 16-17 years.

CONCLUSIONS

In boys and girls, sexual experience increased with age, although this tendency has slowed in recent cohorts. Therefore, early sex education is needed.

Regional Differences in Colorectal Cancer Mortality Between 2000 and 2013 in Republic of Korea

OBJECTIVE

Colorectal cancer (CRC) is the fourth most common site for cancer death in the Republic of Korea. The aim of this study was to describe the trends of colorectal cancer mortality by region.

METHODS

CRC mortality trends in Republic of Korea were described by region using a Joinpoint regression model in both sexes. The annual percent changes (APCs) were calculated for each segment. Visualization of the changes in mortality rate of colorectal cancer death rates by 16 geographic areas in both sexes between 2000-2004 and 2009-2013 were also conducted.

RESULTS

CRC mortality rates of men showed decreasing trend after increase in Daegu, Gyeongsangnam-do, and Chungcheongbuk-do between 2000 and 2013 based on the joinpoint model, while Gwangju, Jeollabuk-do, Jeollanam-do, and Gyeongsangbuk-do showed increase in CRC mortality during the same period. For women, CRC mortality of Seoul, Incheon, Daejeon, and Gyeongsangnam-do started to decrease in 2005, 2003, 2007, and 2006, respectively. The mortality rate for CRC in the eastern regions, which had relatively low rates of CRC among men in 2000 through 2004, reached a level similar to that in the northwestern regions of 2009 through 2013, while the highest CRC mortality rates in women was observed in Chungcheongbuk-do.

CONCLUSIONS

Reduction in CRC mortality varied across 16 metropolitan cities and provinces in men, and the visualization pattern showed that the east side of South Korea had the least progress in mortality reduction.

Time trends of incidence and mortality in colorectal cancer in Changning District, Shanghai, 1975-2013

OBJECTIVE

To evaluate the incidence and mortality of colorectal cancer (CRC) and the estimated patient's age, diagnostic duration and birth cohort effects in patients of Changning District, Shanghai.

METHODS

Age-standardized rates (ASRs) of CRC over eight intervals of 5 years from 1975 to 2013 were determined. Joinpoint regression analysis was used to determine the changes in annual incidence and mortality trends. Age-period-cohort analysis was performed to investigate their effects on the incidence and mortality trends of CRC.

RESULTS

For incidence, the ASRs of 14.14 per 100 000 and 11.81 per 100 000 during 1975-1979 increased to 32.11 per 100 000 and 26.25 per 100 000 in men and women during 2008-2013. For mortality, ASRs of 9.40 per 100 000 and 8.76 per 100 000 increased to 14.80 per 100 000 and 11.92 per 100 000 in men and women, respectively, from 1975-1979 to 2010-2013. Joinpoint regression analysis found an increasing incidence (average annual percentage change [AAPC] 2.18% for men and 1.65% for women) and mortality (AAPC 1.47% for men and 0.97% for women) of CRC throughout the entire period. The incidence and mortality trends of CRC were significantly affected by birth cohorts.

CONCLUSIONS

The increasing incidence and mortality of CRC are largely affected by the effects of birth cohorts. The increased incidence of CRC may be attributed to changes in lifestyle and diet, while that in mortality trends may be resulted from increasing incidence, an aging population and changing lifestyles.

Updates on Cancer Epidemiology in Korea, 2018

Cancer is a major cause of morbidity and the most common cause of death in Korea. There are currently approximately 200,000 incident cancer cases and 78,000 individuals die from cancer every year. The factors directly related to cancer incidence, including aging, smoking, obesity, and Westernized dietary habits, have been increasing during the past several decades. Since 1999, trends toward increased incidence have been observed for thyroid, breast (in women), colorectal, and prostate cancer. Currently, these trends have changed direction, and the incidence of stomach and liver cancer in both sexes, and cervical cancer in women have continually declined. Although the number of cancer deaths increased by a factor of 2.7 from 1983 to 2016, the age-standardized mortality associated with cancer has been decreasing by 3% every year. The 5-year relative survival rate (RSR) has also improved over the past several decades, especially for stomach, prostate, and breast cancer, which had 5-year RSRs greater than 90% in the most recent report.

[Analysis of the age-period-cohort effect on mortality from colorectal cancer in Rio de Janeiro State, Brazil, from 1980 to 2014]

The aim of this study was to estimate the contribution of the effect of age, period, and birth cohort on mortality from colorectal cancer. The study analyzed data on deaths from this cancer in individuals over 35 years of age in Rio de Janeiro State, Brazil, obtained from the Mortality Information System (SIM) from 1980 to 2014. Mortality rates were calculated by gender and age bracket. The effect of age, period, and birth cohort was estimated by the method that uses estimable functions: deviations, curves, and drift in the Epi library of the R software. Standardized mortality rates from colorectal cancer were 27.37/100,000 men and 21.83/100,000 women in 2014. The data showed an increase in mortality from this cancer from 1980 to 2014, and mortality rates were higher in men than in women after the 1990s. Age effect was observed with an increase in the rates and aging. Generational analysis showed lower risk of death in older versus younger cohorts, possibly related to the adoption of the Western lifestyle. This scenario underscores the need for screening strategies aimed at early diagnosis and treatment of precursor lesions.

Colorectal Cancer Staging Using Three Clustering Methods Based on Preoperative Clinical Findings

Determination of the colorectal cancer stage is possible only after surgery based on pathology results. However, sometimes this may prove impossible. The aim of the present study was to determine colorectal cancer stage using three clustering methods based on preoperative clinical findings. All patients referred to the Colorectal Research Center of Shiraz University of Medical Sciences for colorectal cancer surgery during 2006 to 2014 were enrolled in the study. Accordingly, 117 cases participated. Three clustering algorithms were utilized including k-means, hierarchical and fuzzy c-means clustering methods. External validity measures such as sensitivity, specificity and accuracy were used for evaluation of the methods. The results revealed maximum accuracy and sensitivity values for the hierarchical and a maximum specificity value for the fuzzy c-means clustering methods. Furthermore, according to the internal validity measures for the present data set, the optimal number of clusters was two (silhouette coefficient) and the fuzzy c-means algorithm was more appropriate than the k-means clustering approach by increasing the number of clusters.

Age-period-cohort analysis of smoking prevalence among young adults in Korea

OBJECTIVES:

Smoking prevalence among Korean men in their thirties is substantially high (approximately 50%). An in-depth analysis of smoking trends among young adults in their twenties is necessary to devise antismoking policies for the next 10 years. This study aimed to identify the contributions of age, period, and birth cohort effects on smoking prevalence in young adults.

METHODS:

Subjects comprised 181,136 adults (83,947 men: 46.3%; 97,189 women: 53.7%) aged 19 to 30 years from the 2008-2013 Korea Community Health Survey. Smoking prevalence adjusted with reference to the 2008 population was applied to the age-period-cohort (APC) model to identify the independent effects of each factor.

RESULTS:

For men, smoking prevalence rapidly escalated among subjects aged 19 to 22 years and slowed down among those aged 23 to 30 years, declined during 2008 to 2010 but stabilized during 2011 to 2013, and declined in birth cohorts prior to 1988 but stabilized in subjects born after 1988. However, in APC models, smoking prevalence increased with age in the 1988 to 1991 birth cohort. In this birth cohort, smoking prevalence at age 19 to 20 years was approximately 24% but increased to 40% when the subjects turned 23 to 24 years. For women, smoking prevalence was too low to generate consistent results.

CONCLUSIONS:

Over the past six years and in recent birth cohorts, smoking prevalence in adults aged 19 to 30 years has declined and is stable. Smoking prevalence should be more closely followed as it remains susceptible to an increase depending on antismoking policies or social conditions.

Age-period-cohort analysis of the suicide rate in Korea

BACKGROUND

The suicide rate has been increasing in Korea, and the country now has the highest rank in the world. This study aimed to present the long-term trends in Korea's suicide rate using Joinpoint analysis and age-period-cohort (APC) modeling.

METHODS

The population and the number of suicides for each five-year age group were obtained from the National Statistical Office for the period 1984-2013 for Koreans aged 10 years and older. We determined the changes in the trends in age-standardized mortality rates using Joinpoint. APC modeling was performed to describe the trends in the suicide rate using the intrinsic estimator method.

RESULTS

The age-standardized suicide rate in men rapidly increased from 1989 to 2004, and slightly increased thereafter, whereas the suicide rate in women increased from 1989 to 2009 and then decreased thereafter. Within the same period, the suicide rate was higher among the older age groups than in the younger groups. Within the same birth cohort, the suicide rate of the older groups was also higher than that in the younger groups. Within the same age group, the suicide rate of the younger cohorts was higher than it was in the older cohorts. In the APC modeling, old age, recent period, and having been born before 1924 were associated with higher suicide rates.

LIMITATIONS

The accuracy and completeness of the suicide rate data may lead to bias.

CONCLUSIONS

This study showed an increasing trend in the suicide rates for men and women after 1989. These trends may be mainly attributed to cohort effects.