An age and period reconstruction of the HIV epidemic in Italy

Analysis on the trend of AIDS incidence in Zhejiang, China based on the age-period-cohort model (2004-2018)

Objective

To predict the trend of AIDS in specific age groups and to determine the objective population for AIDS screening, this study explored the three transmission routes and characterized each patient group using the APC model based on the whole, local, and immigrant populations in Zhejiang, China.

Methods

The data recruited in this paper was obtained from the national Comprehensive AIDS Prevention and Control Information System - Antiviral Therapy Management database and the Chinese Disease Prevention and Control Information System and the Statistical Yearbook of Zhejiang, China. An APC model was used to estimate the impact of age, period, and cohort on the incidence of AIDS, as well as to predict the AIDS incidence in specific age groups based on different sexes with different transmission routes.

Results

The AIDS incidence peaked in males aged 20–35 years; the incidence of males was higher than that of females due to the impact of period; obvious cohort effect was observed among the immigrants. In the whole and local populations, the incidences of males in all age groups and females in both the 35-year-old group and the whole age group were predicted to increase sharply in 5 years. In the immigrant population, the AIDS incidences in both sexes in all age groups were expected to increase significantly in 5 years. Under the influence of period, the incidence of AIDS via homosexual transmission in the whole population and the local population increased and remained stable after 2015. At the same time, the incidence of AIDS transmitted by homosexual and heterosexual routes in the immigrants also showed an increasing trend.

Conclusions

The results elucidate that there are sex differences in AIDS incidence, and the incidence of AIDS through various transmission routes in all groups is predicted to exhibit an upward trend in the 5 years to come. Effective intervention strategies should be developed and implemented by the public health departments in Zhejiang to control the epidemic of AIDS.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12889-021-11050-x.

A Long-Term Trend Study of Tuberculosis Incidence in China, India and United States 1992-2017: A Joinpoint and Age-Period-Cohort Analysis

Tuberculosis (TB) is one of the major infectious diseases with the largest number of morbidity and mortality. Based on the comparison of high and low burden countries of tuberculosis in China, India and the United States, the influence of age-period-cohort on the incidence of tuberculosis in three countries from 1992 to 2017 was studied based on the Global burden of Disease Study 2017. We studied the trends using Joinpoint regression in the age-standardized incidence rate (ASIR). The regression model showed a significant decreasing behavior in China, India and the United States between 1992 and 2017. Here, we analyzed the tuberculosis incidence trends in China, India, as well as the United States and distinguished age, period and cohort effects by using age-period-cohort (APC) model. We found that the relative risks (RRs) of tuberculosis in China and India have similar trends, but the United States was found different. The period effect showed that the incidence of the three countries as a whole declines with time. The incidence of tuberculosis had increased in most age group. The older the age, the higher the risk of TB incidence. The net age effect in China and India showed a negative trend, while the cohort effect decreased from the earlier birth cohort to the recent birth cohort. Aging may lead to a continuous increase in the incidence of tuberculosis. It is related to the aging of the population and the relative decline of the immune function in the elderly. This should be timely population intervention or vaccine measures, especially for the elderly. The net cohort effect in the United States showed an unfavorable trend, mainly due to rising smoking rates and the emergence of an economic crisis. Reducing tobacco consumption can effectively reduce the incidence.

Age-Period-Cohort Analysis on the Time Trend of Hepatitis B Incidence in Four Prefectures of Southern Xinjiang, China from 2005 to 2017

Objective: The influence of age, period, and cohort on Hepatitis B (HB) incidence in four prefectures of southern Xinjiang, China is still not clear. This paper aims to analyze the long-term trend of the HB incidence in four prefectures of southern Xinjiang, China and to estimate the independent impact of age, period and cohort, as well as to predict the development trend of HB incidence in male and female groups, then to identify the targeted population for HB screening by the model fitting and prediction. Method: The data were from the Case List of HB Cases Reported in the Infectious Disease Reporting Information Management System and the Xinjiang Statistical Yearbook of China. The age-period-cohort (APC) model was used to estimate the impacts of age, period and cohort on HB incidence, which could be used to predict the HB incidence in specific age groups of men and women. Results: Under the influence of age effect, the incidence of HB in males had two peaks (20–35 years old and 60–80 years old), the influence of age effect on the incidence of HB in females was lower than that of males and the obvious peak was between 20–30 years old; the period effect on the HB incidence in males and females fluctuated greatly and the fluctuation degree of influence on males was bigger than that of women. The HB incidence among males and females in the four regions tended to be affected by cohort effect, which reached a peak after 1990 and then declined sharply and gradually became stabilized. By predicting the HB incidence from 2018 to 2022, we found that there were significant differences in HB incidence among people over 35 years old, under 35 years old and the whole population in four prefectures of southern Xinjiang, China. Conclusions: Although the incidence of HB in some regions shows a downward trend, there is still an obvious upward trend of incidences in other places. In our paper, results indicate that the burden of HB incidence may be extended in the future, so we hope this can draw the attention of relative departments. These results reveal the differences of incidence between males and females as well, so respective measures of the two groups’ functions are essential.

Increasing varicella incidence rates among children in the Republic of Korea: an age-period-cohort analysis

In the Republic of Korea, despite the introduction of one-dose universal varicella vaccination in 2005 and achieving a high coverage rate of 98.9% in 2012, the incidence rate has been increased sevenfold. This study aimed to investigate time trends of varicella incidence rate, assessing the age, period and birth cohort effects. We used national data on the annual number of reported cases from 2006 to 2017. A log-linear Poisson regression model was used to estimate age-period-cohort effects on varicella incidence rate. From 2006 to 2017, the incidence of varicella increased from 22.5 cases to more than 154.8 cases per 100 000. Peak incidence has shifted from 4 to 6 years old. The estimated period and cohort effects showed significant upward patterns, with a linear increasing trend by net drift. There has been an increase in the incidence among the Korean population regarding period and cohort despite the universal vaccination of varicella vaccine. Our data suggest the need for additional studies to address the current gap in herd immunity.

Age-period cohort analysis of AIDS incidence rates in Rio de Janeiro, Brazil, 1985-2009

INTRODUCTION

The long average incubation time from HIV infection to AIDS makes it difficult to estimate the recent tendencies of HIV from AIDS incidence data. The objective of this study was to investigate the effects of three temporal components in AIDS incidence in the state of Rio de Janeiro, Brazil - age, period, and cohort.

METHODS

Age-specific AIDS incidence rates per 100,000 from Rio de Janeiro (Brazil) were calculated for both sexes using five-year age classes from 1985 to 2009 based on reported data from the Notifiable Disease Information System of the Brazilian Ministry of Health and from census population counts. Multivariate negative binomial models were used to analyze the risk of AIDS by age, period, and birth cohort.

RESULTS

From 1985 to 2009, AIDS incidence initially increased with age in each birth cohort and then decreased (except for individuals born from 1971-1979 to 1986-1994). High peaks in the rates in each birth cohort were detected in 1995-1999 for males and in 2000-2004 for females. Multivariate analysis showed the maximum risk of AIDS in the 30-34 age group and 1958-1962 birth cohort.

CONCLUSION

Age, birth cohort, and period effects all may have influenced the AIDS incidence rates over the period investigated. From 1985 to 1999, comparison of the tendencies (by age) of the period with the birth cohort revealed opposing tendencies in individuals older than 29 years and in the youngest age groups (0 to 14 years). From 2000 to 2009, a strong age effect can be observed in both sexes. Consistent changes in period tendency curves suggest the occurrence of period effects. A reduction in the intensity of the risk of AIDS can be observed after 2000-2004.

Bayesian approach to predicting cancer incidence for an area without cancer registration by using cancer incidence data from nearby areas

This paper compares three different methods for performing cancer incidence prediction in an area without a cancer registry under a Bayesian framework, using linear and log-linear age-period models with either age-specific slopes or a common slope across age groups. The three methods assume that a nearby area with a cancer registration has similar incidence and mortality patterns as the area of interest without a cancer registry where the cancer incidence prediction is carried out. The three methods differ in modeling strategies: (i) modeling the incidence rate directly; (ii) modeling the ratio of the number of incident cases to that of mortality cases; and (iii) modeling the difference between the incidence rate and the mortality rate. Strategy (iii) is a new approach in this type of projection. Empirical assessment is made using real data from the cancer registry of Tarragona, Spain, to predict cancer incidence in Girona, Spain, and vice versa. Predictions of short-term (3-4 years) incidence were made for 2001 in Tarragona using observed cancer incidence and mortality data for 1994-1998 from Girona. Short-term predictions were made for 2002 in Girona using Tarragona's 1994-1998 data. Additionally, long-term (10 years) incidence rate predictions were made for 2002 in Girona using data from Tarragona for the period 1985-1992. Our results suggest that extrapolating time-trends of incidence rates minus mortality rates may have the best predictive performance overall. These methods of population-level disease-incidence prediction are highly relevant to health care planning and policy decisions.

Estimating the cumulative number of human immunodeficiency virus diagnoses by cross-linking from four different sources

BACKGROUND

We estimated the cumulative number of people diagnosed with human immunodeficiency virus (HIV) infection in a region of Italy by cross-linking data from four surveillance systems and applying capture-recapture methods.

METHODS

The study was conducted using data referring to residents of the Veneto Region (population 4.4 million). We cross-linked data from the AIDS Registry (data 1983-2000), the HIV Registry (1988-2000), the Death Registry (1992-1999), and the Hospital-Discharge Registry (1997-2000), using a code based on name, birth date, and sex. A specific software for capture-recapture models (CARE-1) was used to estimate the size of the target population with two different statistical approaches (sample coverage and log-linear models).

RESULTS

A total of 2801 people were reported to the AIDS Registry, 6415 to the HIV Registry, 1598 to the Death Registry as HIV/AIDS-related deaths, and 3330 to the Hospital-Discharge Registry with a diagnosis of HIV infection. Overall, 8723 people were present in at least one registry: 4896 people were present in only one registry, 2387 in two registries, 1286 in three registries, and 154 in all four registries. Using the sample coverage approach, we estimated that, since the beginning of the epidemic in Veneto, an estimated 11 281 people (95% CI: 10 981, 11 621) should have been reported to at least one registry; thus the estimated coverage of the four registries was 77.3% (i.e. 8723/11 281). Results obtained applying the log-linear approach were similar, although the fitting of this model was not adequate.

CONCLUSIONS

Cross-linking data from four different sources and applying the capture-recapture method can improve the accuracy of the estimates of the dimensions of the HIV epidemic.

Uncertainty of AIDS incubation time and its effects on back-calculation estimates

Incubation time is the period from the onset of HIV infection to AIDS. The distribution of the incubation time is one of the main parameters of the back-calculation method for the estimation of incidence of HIV infection. Because of the long and variable incubation time, the assessment of its distribution is uncertain and this uncertainty spreads through the back-calculation method and affects the estimation of the precision of incidence of HIV infection. We propose a method to investigate the sensitivity of the estimates to variations of the incubation times, with particular regard to the covariate AGE in the modelling of the incubation period, making use of the parametric bootstrap. An application to the HIV epidemic in Italy is presented. The amplification of the uncertainty of the HIV incidence estimates resulting from the implementation of our proposed method tends to concentrate around the earlier periods of the epidemic, corresponding to the right tail of the incubation time distribution, which is very sensitive to small perturbations.

A non-parametric method for the reconstruction of age- and time-dependent incidence from the prevalence data of irreversible diseases with differential mortality

A method is proposed for reconstructing the time and age dependence of incidence rates from successive age-prevalence cross sections taken from the sentinel surveys of irreversible diseases when there is an important difference in mortality between the infected and susceptible subpopulations. The prevalence information at different time-age points is used to generate a surface; the time-age variations along the life line profiles of this surface and the difference in mortality rates are used to reconstruct the time and age dependence of the incidence rate. Past attempts were based on specified parametric forms for the incidence or on the hypothesis of time-invariant forms for the age-prevalence cross sections. The proposed method makes no such assumptions and is thus capable of coping with rapidly evolving prevalence situations. In the simulations carried out, it is found to be resilient to important random noise components added to a prescribed incidence rate input. The method is also tested on a real data set of successive HIV age-prevalence cross sections from Burundi coupled to differential mortality data on HIV(+) and HIV(-) individuals. The often-made assumption that the incidence rate can be written as the product of a calendar time component and an age component is also examined. In this case, a pooling procedure is proposed to estimate the time and the age profiles of the incidence rate using the reconstructed incidence rates at all time-age points.

A hierarchical Bayesian approach to age-specific back-calculation of cancer incidence rates

We propose a Bayesian hierarchical model to estimate age-specific cancer incidence per year from age-specific cancer mortality. The model is based upon the empirical Bayesian approach of Liao and Brookmeyer (1995) and extends that model by consideration of the dependence on age. The incident cases per year are considered as observations from a discrete-time stochastic process following an autoregressive structure within a Poisson regression model. The model assumes that the survival probability among those with cancer is known. We have investigated the sensitivity of the model to the choice of this distribution and have found that this is the most sensitive part of the model. By comparison the predictions of the model are relatively robust to changes in other key areas, such as the number of years an incident case contributes before death, assumptions about parameter equality for identification and the initial prior distributions. The proposed methodology has been investigated using lung cancer mortality data from Scotland. Parameter estimates were obtained through Markov chain Monte Carlo methods, implemented using BUGS.

The impact of the 1993 European revision of the AIDS case definition on back-calculation estimates: an application in Italy

OBJECTIVES

The revision of the case definition for AIDS within a given observation period causes discontinuity points on the epidemic curve to which back-calculation procedures can be sensitive. The aim of this work is to characterize the impact of the 1993 European revision of AIDS case definition and to evaluate the degree of distortion by which back-calculation estimates obtained on Italian data are affected.

METHODS

The back-calculation procedure used, is a generalization of standard methods for estimating and projecting the AIDS epidemic. Age at onset of HIV infection, incubation time distribution, susceptible population and competitive non-AIDS mortality rates for infected persons are included in the estimation process.

RESULTS

Back-calculation estimates resulted to be sensitive to the discontinuity point that the 1993 revision of AIDS case definition induced on the epidemic curve. The resulting effect is a tendency to overestimate HIV incidence in recent years by 20-40%. The maximum effect was found using data with end of AIDS cases at December 1993. The overestimation is a transient effect, that is, it is expected to almost disappear in 1995-1996.

CONCLUSIONS

The introduction of the 1993 European revision of AIDS case definition caused distortion of back-calculation estimates in Italy, leading to overestimate incidence and prevalence of HIV infection for recent years. It is believed that this effect has occurred in all countries that adopted the 1993 European revision of AIDS case definition, and its characterization is potentially useful for further changes of AIDS case definition in the future.

The changing distribution of HIV infection: HIV surveillance in Lazio, Italy, 1985 through 1994. Lazio HIV Surveillance Collaborative Group

OBJECTIVES

This study sought to describe the human immunodeficiency virus (HIV) surveillance system in Lazio, Italy, and to analyze exposure patterns and time trends of HIV serodiagnoses from January 1985 to December 1994.

METHODS

A linkage procedure made it possible to identify newly diagnosed HIV cases. Anonymous information was collected on demographic and exposure factors for each individual.

RESULTS

Of 35,425 reports, 13,660 were newly diagnosed HIV cases, 70.9% of them in men. The proportion of women increased at the beginning of the study period (the male:female ratio declined from 3.5 in 1985 to 2.6 in 1986) and then remained stable. The proportion of subjects reporting heterosexual exposure, in men and women, respectively, increased from 1.5% and 2.0% in 1985 to 21.2% and 60.8% in 1994. Starting in 1992, heterosexual contact has become the main transmission route for women.

CONCLUSIONS

A changing pattern in the HIV epidemic is emerging, with a shift in the incidence of HIV diagnosis from "core" high-risk groups (drug injectors) to the large low-risk population (the general population) exposed through heterosexual transmission. This is probably occurring in other areas (e.g., large urban centers in the United States) with a similar epidemiological situation.

The AIDS epidemic among Spanish drug users: a birth cohort-associated phenomenon

OBJECTIVES

In Spain the number of new acquired immunodeficiency syndrome (AIDS) cases among injection drug users continues to rise. The time trend up to 1994 has been analyzed, with special attention paid to the different generations.

METHODS

The source for injection drug use-related cases was the Spanish AIDS Register. Independent analyses of annual specific rates were run for each sex with the use of an age-period-cohort log-linear model.

RESULTS

After adjustment for age and year of diagnosis, AIDS incidence related to injection drug use is associated with specific birth cohorts. Rising values are observed in the successive generations born during the 1950s, peaking in men born in 1962 and women born in 1964. In subsequent cohorts, there is a marked falloff in incidence for both sexes, but this decline is seen to halt in men from the 1972 birth cohort onwards. The overall period effect is upward, yet the trend flattens in the last years. There is a pronounced age effect with maximum values in men and women at ages 29 and 27, respectively.

CONCLUSIONS

It is essential to urge avoidance of risk behaviors in new generations.

A persistent rise in mortality among injection drug users in Rome, 1980 through 1992

OBJECTIVES

The purpose of the study was to analyze overall and cause-specific mortality among injection drug users in Rome.

METHODS

A cohort of 4200 injection drug users was enrolled in drug treatment centers from 1980 through 1988 and followed up until December 1992.

RESULTS

The age-adjusted mortality rate from all causes increased from 7.8/1000 person-years in 1985/86 to 27.7/1000 in 1991/92. The rise was mainly attributable to acquired immunodeficiency syndrome (AIDS), but mortality from overdose and other causes increased as well. The cumulative risk of death by the age of 40 was 29.3%.

CONCLUSIONS

The impact of AIDS deaths appears to be additional to a persistent increase of mortality for all other causes.

Estimating population-based incidence and prevalence of major coronary events

Population-based data on major coronary events (MCE) are generally lacking for large areas, such as at the nationwide level. While mortality data are currently and exhaustively collected in all developed countries and in most developing countries, incidence and prevalence are often available only for certain subgroups of the population under study. We propose a mathematical method to estimate incidence and prevalence using morality and survival data as input, and to forecast MCE occurrence using an age, period, and cohort approach. An application of the method is given to reconstruct incidence and prevalence of MCE in Italy from 1970 to 1990 and to project trends up to the year 2000. MCE incidence has been decreasing since 1974, four years before the observed mortality decline. Conversely, prevalence continues to increase up to the middle of the 1980, and declines thereafter.

Scope of the AIDS epidemic in the United States

Two-dimensional deconvolution techniques are used here to reconstruct age-specific human immunodeficiency virus (HIV) infection rates in the United States from surveillance data on acquired immunodeficiency syndrome (AIDS). This approach suggests that 630,000 to 897,000 adults and adolescents in the United States were living with HIV infection as of January 1993, including 107,000 to 150,000 women. The estimated incidence of HIV infection declined markedly over time among white males, especially those older than 30 years. In contrast, HIV incidence appears to have remained relatively constant among women and minorities. As of January 1993, prevalence was highest among young adults in their late twenties and thirties and among minorities. An estimated 3 percent of black men and 1 percent of black women in their thirties were living with HIV infection as of that date. If infection rates remain at these levels, HIV must be considered as endemic in the United States.

MIAMOD: a computer package to estimate chronic disease morbidity using mortality and survival data

The MIAMOD package is for use in epidemiological analysis of chronic degenerative diseases. The package has been designed to use survival and mortality data supplied by the user, to estimate incidence and prevalence rates, to forecast future mortality and morbidity levels and to provide life tables. Estimates are derived by modelling incidence as an age-period-cohort function and by the equations relating specific cause mortality and prevalence to incidence and survival. The model parameters are evaluated by fitting mortality data by means of a weighted non-linear regression model. Numerical and statistical methods used to solve the regression and to compute standard errors, projections, and life tables are discussed. The program is written in standard FORTRAN 77 and runs on a mainframe computer. The different program units are illustrated together with the principal implementation options. An example of application is provided to show a typical output pattern.