Age, cohort and period effects on large bowel cancer incidence

Mortality trends of bladder cancer in China from 1991 to 2015: an age-period-cohort analysis

Purpose

The effects of age, period, and cohort on mortality rates of bladder cancer in China remained vague. This study aimed to analyze the secular trends of bladder cancer mortality in China and estimate the independent effects of age, period, and cohort.

Methods

Data for bladder cancer mortality from 1991 to 2015 was obtained from the WHO Mortality Database and China Health Statistical Yearbook. The age-period-cohort model was used to estimate the effect of age, period, and cohort. The intrinsic estimator method was used to solve the nonidentification problem of collinearity among age, period, and cohort.

Results

The age-standardized mortality rates of total residents (2.33–1.87/100,000), male (3.45–2.89/100,000), and female (1.24–0.82/100,000) showed decreasing trends, which was more obvious in males than in females. Age effects increased consistently with age in all age groups (coefficients: −2.02 to 1.91 in the total population, −2.06 to 2.02 in males and −2.04 to 1.81 in females). Cohort effects decreased overall (coefficients: 0.96 to −1.62 in the total population, 1.11 to −1.66 in males and 0.78 to −1.46 in females). Period effects were not found in China.

Conclusion

Although a decreasing mortality was observed, the bladder cancer burden in China will likely increase in the next few years due to population aging, environmental pollution, and food safety. The findings suggested that preventive measures should be taken corresponding to the changes in age-and cohort-related factors in the population.

Cancer Mortality in Córdoba, Argentina, 1986–2006: An Age-Period-Cohort Analysis

Aims and background

Cancer is the second main cause of death in Argentina, surpassed only by cardiovascular disease. However, analytical approaches isolating some of the known effects, such as age at death, period of death and birth cohort, have never been performed in cancer mortality studies in Argentina. The aim of this study was to analyze cancer mortality trends in a representative region of the country, the Córdoba province (1986–2006).

Methods and study design

Overall age-standardized (world population) mortality rates for cancer (all sites) were computed by a direct method. Joinpoint regression was fitted to the age-standardized mortality rates for both sexes to provide estimated and 95% confidence intervals of the annual percentage changes. The effects of age (15 age groups), period of death (1986–90, 1991–95, 1996–00 or 2001–06), and birth cohort (18 overlapping 10-year birth cohorts) covariates on mortality rates were estimated using a sequentially fitted Poisson regression model.

Results

During the study period, 102,737 people died of cancer in Córdoba, with the age-standardized mortality rates decreasing from 139.3 to 118.7/100,000 person-years. Although this reduction was more noticeable in men, the joinpoint regression model showed a significant change of the age-standardized mortality rates after 1996 in both sexes. Age-period-cohort analysis suggested that the cancer mortality trends may be linked with a strong age effect and a moderate or mild period and cohort effect, related to sex and place of residence.

Conclusions

Based on the observed cohort effect, it maybe argued that there has been a lower exposure level to some risk factors, such as diet and other environmental factors, in Cordoba over the last decades.

Prostate cancer mortality trends in Argentina 1986-2006: an age-period-cohort and joinpoint analysis

The aim of this study was to give an overview of the magnitude, variation by age and time trends in the rates of prostate cancer mortality in Córdoba province and in Argentina as a whole from 1986 to 2006. Mortality data were provided by the Córdoba Ministry of Health and the World Health Organization cancer mortality database. Prostate cancer mortality time trends were analyzed using joinpoint analysis and age-period-cohort models. In Argentina prostate cancer age-standardized mortality rates rose by 1% and 3.4% per year from 1986 to 1992 and from 1992 to 1998 respectively. There was a decreasing trend (-1.6%) for Argentina from 1998 and Córdoba (-1.9%) from 1995. Age-period-cohort models for the country and the province showed a strong age effect. In the country there was an increased risk in the 1996-2000 period, whereas there was decreased risk for birth cohorts since 1946, principally in Córdoba. A decreasing trend in prostate cancer mortality was found in Córdoba as well as in Argentina, which might be attributed to the improvement in treatment in this country.

Bladder cancer mortality trends and patterns in Córdoba, Argentina (1986-2006)

BACKGROUND

Bladder cancer is common worldwide and the fourth most commonly diagnosed malignancy in men in Argentina.

OBJECTIVE

To describe bladder cancer mortality trends in Córdoba (1986-2006), considering the effect of age, period, and cohort, and to estimate the effect of arsenic exposure on bladder cancer, and its interaction with sex, while controlling by smoking habits and space and time variation of the rates.

METHODS

A joinpoint regression was performed to compute the estimated annual percentage changes (EAPC) of the age-standardized mortality rates (ASMR) in an adult population from Córdoba, Argentina. A Poisson model was fitted to estimate the effect of age, period, and cohort. The influence of gender, tobacco smoking (using lung cancer ASMR as surrogate), and arsenic in drinking water was examined using a hierarchical model.

RESULTS

A favorable trend (1986-2006) in bladder cancer ASMR in both sexes was found: EAPC of -2.54 in men and -1.69 in women. There was a decreasing trend in relative risk (RR) for cohorts born in 1931 or after. The multilevel model showed an increasing risk for each increase in lung cancer ASMR unit (RR = 1.001) and a biological interaction between sex and arsenic exposure. RR was higher among men exposed to increasing As-exposure categories (RR male low exposure 3.14, RR male intermediate exposure 4.03, RR male high exposure 4.71 versus female low exposure). A non-random space-time distribution of the rates was observed.

CONCLUSIONS

There has been a decreasing trend in ASMR for bladder cancer in Córdoba. This study confirms that bladder cancer is associated with age, gender, smoking habit, and exposure to arsenic. Moreover, an effect measure modification between exposure to arsenic and sex was found.

Breast cancer mortality trends and patterns in Córdoba, Argentina in the period 1986-2006

To estimate the mortality trends and spatial patterns for breast cancer in Córdoba (Argentina) in the period 1986-2006 taking into account age, calendar year, and birth cohort effects. Mortality data were provided by the Department of Statistics, Ministry of Health of Córdoba. Time trends in breast cancer mortality were analyzed using joinpoint analysis and age-period-cohort models. A random-intercept log-linear model was also used to assess the spatial pattern. Breast cancer age standardized mortality rates rose by 1.4% (95% confidence interval 0.2-2.6) per year from 1986 to 1997, and thereafter both breast and total cancer rates declined [-2.5% (-4 to -1.0) and -1.6% (-2.3 to -0.8), respectively]. In age-specific analysis the decline was mainly at age 20-49 years [-2.4% (-4 to -0.9)]. Rates over most recent calendar years decreased, mainly in the most urbanized districts. Age-period-cohort models for Córdoba province and Córdoba Capital showed a favorable cohort effect for generations born after 1955. A decreasing trend in breast cancer mortality was found in Córdoba, especially at younger ages and in most urbanized areas. This could be attributed to some unidentified favorable factors in generations born after 1955.