Trends and future projections of cervical cancer-related outcomes in Japan: What happens if the HPV vaccine program is not implemented?

Contrary to other developed countries, in Japan, recent years have seen increases in cervical cancer incidence and mortality among young people. However, the human papillomavirus (HPV) vaccine program, a key measure for avoiding cervical cancer, has been virtually suspended. Temporal changes in cervical cancer profiles in this unique situation have not been fully investigated epidemiologically. Our study aimed to determine the current status and future trends of the incidence and mortality of cervical cancer and precancerous lesions in Japan. Mortality rates of cervical cancer during 1975 to 2016 and incidence rates of cervical cancer and cervical intraepithelial neoplasia (CIN) 3 during 1975 to 2013 were examined using vital statistics and population-based cancer registry data in Japan. Bayesian age-period-cohort analyses were performed to analyze temporal changes of the three cervical cancer-related outcomes. We also calculated projections to 2028 for the three outcomes, assuming that HPV vaccination coverage and screening rates in Japan would be maintained at the current level after the resumption of the national vaccination program. The risk of occurrence of the three outcomes showed similar changes by birth cohort, peaking in the mid-1890s to 1900s birth cohorts, declining sharply in the 1940s birth cohort, and persistently increasing in the 1950s and later birth cohorts. Projections to 2028 show increases in cervical cancer incidence and mortality in the 30 to 69 age group, with a particular increase in CIN3 incidence in the 25 to 49 age group, if HPV vaccine programs and screening are not effectively implemented. These findings revealed an increasing cervical disease burden among reproductive age females in Japan.

[Effects of age, period, and cohort on the trends in obesity rate and energy intake ratio from fat in Japanese adults].

OBJECTIVES: In the present study, we aimed to clarify the specific effects of age, period, and cohort on trends in obesity rate and energy intake ratio from fat in Japanese adults using a Bayesian age-period-cohort (APC) analysis and to evaluate the relationship between changes in obesity rate and energy intake ratio from fat. METHODS: We obtained data regarding obesity rate and calorie intake of fat, animal fat, carbohydrate, protein, animal protein, and total energy intake of Japanese adults from the National Nutrition Survey. The data were tabulated for five 10-year age groups (from 20-29 years to 60-69 years) and 17 annual demographic profiles (from 1995 to 2011), with regard to the energy intake ratio. These standard cohort tables were analyzed using a Bayesian APC model. RESULTS: With regard to obesity rate, the effect of age was the greatest and increased rapidly in the age group of 30-39 years for both genders. Moreover, the period effect consistently increased in men, but had very little variation in women. The cohort effect indicated a reverse of the decreasing trend in the cohorts born after 1962-1971 in men and indicated a reverse of the increasing trend in the cohorts born after 1965-1974 in women. With regard to the energy intake ratio from fat, the trends for the three effects differed from those for obesity rate for both genders. The age effect generally decreased with increasing age. Furthermore, for both genders, the period effect gradually decreased after 1998 and markedly decreased in 2001, remained constant or slightly increased until 2008, and increased thereafter. However, the cohort effect was the greatest among the three, and although a decreasing trend was observed in the cohorts born after 1976-1985 in women, the energy intake from fat increased in the younger cohorts in both genders. The overall effect on energy intake ratio from animal fat had a slope similar to that of the energy intake ratio from fat. CONCLUSION: Each effect affected obesity and energy intake ratio from fat in a different manner, suggesting that factors other than energy intake ratio from fat, such as energy expenditure, contributed to the changes in obesity rate. However, obesity risk markedly increased in the age group of 30-39 years, and younger generations had a higher energy intake ratio from fat. These results suggest that dietary guidelines, particularly the optimal intake of animal products, is needed for younger generations to prevent the development of obesity in adulthood.

[The effects of age, period, and birth cohorts on the rates of overweight and underweight students in 1977-2006 and a prediction of the rates in 2007-2016].

OBJECTIVES: The increase in the overweight or underweight student population in Japanese schools is an important health issue. To assess the independent effects of age, period, and birth cohorts, we analyzed trends in the rates of overweight and underweight students from 1977 to 2006 using a Bayesian age-period-cohort (APC) analysis. Additionally, we predicted the rates overweight and underweight students in 2007-2016. METHODS: We created a data set of the rates of overweight and underweight students aged 6-14 years using the annual school health survey report data. We then analyzed a cohort table that plotted age against calendar time using a Bayesian APC model. We also made a prediction of the rates of overweight and underweight students in 2007-2016. RESULTS: For overweight students, the age effect increased from 6 to 11 years of age for male students and from 6 to 12 years of age for female students; thereafter, the effects decreased. The period effects consistently increased until late 1990, and decreased thereafter for both male and female students. The cohort effects increased for male students born between 1963 and 1969, and later decreased for those born in 1981. However, this trend for male students later increased. For female students, the cohort effects decreased for those born between 1963 and 1975, and later increased for those born in 1990, indicating a plateau or slight increase in the trend. For underweight students, the age effect in male students increased from 7 to 10 years of age, and then plateaued; whereas, the age effect increased from 7 to 12 years of age for female students before reaching a plateau. The period effects increased consistently by 2000 and decreased slightly in both male and female students. The birth cohort effect in male students increased for those born after the mid-1980s, and then plateaued in the early 1990s. The cohort effect increased for female students born after 1984, and then plateaued in 1993. The projections for the rates of overweight and underweight student population indicated a steady trend until 2016. CONCLUSION: The rate of overweight and underweight students was strongly influenced by age; however, period and birth cohort also played a role. The projections for the rates of overweight and underweight students indicated a steady trend until 2016. These results suggest that strategies based on age-, period-, and cohort-specific measures may be required for future interventions for preventing overweight and underweight among students.

[Age-, period-, and birth-cohort-specific effects on the male proportion in Japanese newborns and projections for male proportion for 20 periods (2008-2027)].

OBJECTIVES: To determine the age-, period-, and cohort-specific effects on the male proportion in Japanese newborns, we performed an age-period-cohort (APC) analysis in this study. In addition, projections for the male proportion were analyzed. METHODS: We obtained data on live births of newborns for Japanese women in 1947-2007 from the National Vital Statistics. Cohort tables containing data on the male proportion were analyzed using a Bayesian APC model. Projections of the male proportion (2008-2027) were calculated. RESULTS: The age effect decreased when the mothers were 40-44 years old; however, the effect was relatively limited as compared with the period and cohort effects. The period effect increased from 1947 to 1969 and decreased thereafter. Analysis of the cohort effect on male proportion trends revealed a decreasing slope for birth cohorts born between 1905 and 1945 and a subsequent increase after 1958. The projections for male proportion indicated that the male proportion in 2027 would be similar to that in the 1970s. CONCLUSIONS: The age of the mother hardly affected the male proportion. The period effect started decreasing from the latter half of the 1960s. This may be attributable to the high economic growth since 1965 that promoted industrial development that led to environmental pollution, which in turn may have lead to the deterioration of the intrauterine environment. Cohort effects changed from 1958 and exhibited trends toward increase in male proportion; this may be due to improvements in obstetric care. Our results suggest that the male proportion in Japanese newborns will increase in the future.

[Age, period and birth-cohort effects on marriage rates in Japanese women between 1985 and 2005, and comparison of trends of effects between marriage and birth rates].

OBJECTIVE: An age-period-cohort (APC) analysis was performed to provide information about age-, period-, and cohort-specific effects on marriage trends in Japanese women. In addition, the relationships of the trends of age-, period-, and cohort-specific effects between marriage and birth were analyzed. METHODS: We obtained data regarding marriages of Japanese women aged between 19 and 38 years for the period of 1985 to 2005 from the National Vital Statistics. Population data used were for an estimated population, obtained from the Population Estimates Annual Reports. Standard cohort tables comprising marriage and population data were analyzed using a Bayesian APC model to identify age-, period-, and cohort-specific effects on marriage rate trends. Previously obtained data for a similar APC-analysis of birth trends were used to compare the trends in the effects of age, period, and cohort on marriage and birth patterns. For this purpose, the estimated values for each effect were normalized. RESULTS: With regard to the marriage trends in Japanese women, the effect of age was the greatest, peaking at the age of 25 years. The period effect increased after 1997; however, its effect was relatively limited as compared to the other effects. The cohort effect, which was greater than the period effect and less than the age effect, on marriage trends showed a decreasing slope for birth cohorts born after 1966 and subsequent increase after 1982. Comparison of age, period and cohort effects between the trends in marriage and birth rates showed that the age effect distinctly peaked at 25 and 28 years for marriage and births, respectively. The period effect on marriage and birth showed a decreasing trend until 1991 and subsequent increased in 1992 and 1997 for births and marriage, respectively. With regard to the cohort effect on birth rates, a decreasing trend was observed for the birth cohorts after 1961, with increase after 1977. However, with regard to the cohort effect on marriage rates, the decreasing trend observed for birth cohorts after 1966 showed an increase after 1982. CONCLUSION: Among age, period, and birth cohort, age is the most influential factor affecting marriage rates. Period effects appear relatively small, but they increased after 1997. Cohort effects reduced for birth cohorts born after 1966 and subsequently increased after 1982. Results of the comparison study showed that changing patterns of age, period and cohort effects had very similar influences on the trends for marriage and birth rates. However, a 3-year difference was observed between the peaks of the age effect on the two rates. A time lag of 5 years was observed between the turning point in the trend of period effects for marriage and birth rates. The changing patterns of cohort effects on marriage and birth rates were similar, but the turning point for the marriage pattern occurred in a 5-year younger cohort compared with the birth pattern.

[Gender Differences in Projected Life Expectancy in Japan (2023-2047) Determined by Bayesian Age-Period-Cohort Analysis].

OBJECTIVES: In this study, we aimed to (1) determine the effects of age, period, and cohort on mortality rate trends between 1958 and 2012 in Japan and (2) assess gender differences in projected life expectancy (LE) for the 2023-2047 period. METHODS: A time trend study was conducted using age-period-cohort (APC) analysis. A Bayesian APC model was fitted to describe mortality rate trends for the 1958-2012 period and to project mortality rates for 2023-2047. LE was predicted by Chiang's method using projected mortality rates. RESULTS: Age, period, and cohort effects showed similar patterns between males and females. As time passes, gender differences in projected LE were larger among individuals over 65 years than among those under 65 years. Time series change rates of the extension of projected LE after excluding specific causes of death showed the following: smaller extension of projected LE in males in terms of mortality risk from malignant neoplasms, heart diseases, pneumonia, and accidents (under 65 years) and in females in terms of mortality risk from heart diseases, cerebrovascular diseases, and suicide (over 65 years). CONCLUSIONS: Gender differences in projected LE are expected to be smaller before middle age and to be larger among seniors. These projected gender differences stem in part from the lower mortality risk among men than among women from malignant neoplasms, heart diseases, pneumonia, and accidents (under 65 years), and among women compared to men from heart disease, cerebrovascular disease, and suicide (over 65 years).

Intra- and inter-laboratory variation in the scoring of micronuclei and nucleoplasmic bridges in binucleated human lymphocytes. Results of an international slide-scoring exercise by the HUMN project.

One of the objectives of the HUman MicroNucleus (HUMN) project is to identify the methodological variables that have an important impact on micronucleus (MN) or micronucleated (MNed) cell frequencies measured in human lymphocytes using the cytokinesis-block micronucleus assay. In a previous study we had shown that the scoring criteria used were likely to be an important variable. To determine the extent of residual variation when laboratories scored cells from the same cultures using the same set of standard scoring criteria, an inter-laboratory slide-scoring exercise was performed among 34 laboratories from 21 countries with a total of 51 slide scorers involved. The results of this study show that even under these optimized conditions there is a great variation in the MN frequency or MNed cell frequency obtained by individual laboratories and scorers. All laboratories ranked correctly the MNed cell frequency in cells from cultures that were unirradiated, or exposed to 1 or 2Gy of gamma rays. The study also estimated that the intra-scorer median coefficient of variation for duplicate MNed cell frequency scores is 29% for unexposed cultures and 14 and 11% for cells exposed to 1 and 2Gy, respectively. These values can be used as a standard for quality or acceptability of data in future studies. Using a Poisson regression model it was estimated that radiation dose explained 67% of the variance, while staining method, cell sample, laboratory, and covariance explained 0.6, 0.3, 6.5, and 25.6% of the variance, respectively, leaving only 3.1% of the variance unexplained. As part of this exercise, nucleoplasmic bridges were also estimated by the laboratories; however, inexperience in the use of this biomarker of chromosome rearrangement was reflected in the much greater heterogeneity in the data and the unexplained variation estimated by the Poisson model. The results of these studies indicate clearly that even after standardizing culture and scoring conditions it will be necessary to calibrate scorers and laboratories if MN, MNed cell and nucleoplasmic bridge frequencies are to be reliably compared among laboratories and among populations.

Age, period, and birth cohort-specific effects on cervical cancer mortality rates in Japanese women and projections for mortality rates over 20-year period (2012-2031).

OBJECTIVES: We aimed to determine the effects of age, period, and birth cohort on cervical cancer mortality rate trends in Japanese women, by age-period-cohort (APC) analysis. Additionally, we analyzed projected mortality rates. METHODS: We obtained data on the number of cervical cancer deaths in Japanese women from 1975-2011 from the national vital statistics and census population data. A cohort table of mortality rate data was analyzed on the basis of a Bayesian APC model. We also projected the mortality rates for the 2012-2031 period. RESULTS: The period effect was relatively limited, compared with the age and cohort effects. The age effect increased suddenly from 25-29 to 45-49 years of age and gently increased thereafter. An analysis of the cohort effect on mortality rate trends revealed a steep decreasing slope for birth cohorts born from 1908-1940 and a subsequent sudden increase after 1945. The mortality rate projections indicated increasing trends from 40 to 74 years of age until the year 2031. CONCLUSIONS: The age effect increased from 25-29 years of age. This could be attributable to the high human papilloma virus (HPV) infection risk and the low cervical cancer screening rate. The cohort effect changed from decreasing to increasing after the early 1940s. This might be attributable to the spread of cervical cancer screening and treatment before 1940 and the high HPV infection risk and reduced cervical cancer screening rate after 1945. The projected mortality rate indicated an increasing trend until the year 2031.

Gender differences in age, period, and birth-cohort effects on the suicide mortality rate in Japan, 1985-2006.

Because suicide is increasingly becoming a public health threat in Japan, it is necessary to identify high-risk groups to develop effective preventive measures. The suicide mortality trends from 1985 to 2006 for Japanese aged between 15 and 79 years were analyzed by a Bayesian age-period-cohort analysis to evaluate the independent effects of age, period, and birth cohort. Age-specific effect showed an overall increase with age in both genders, but a distinct increase was noted only among men aged between 50 and 64 years. The period effect exhibited a sudden rise in 1998; this effect was more apparent in men than in women. The cohort-specific effect increased in male birth cohorts born after 1926 and in female birth cohorts born after 1956. In conclusion, a gender difference was detected in the effects of age, period, and cohort on suicide risk among Japanese.