Evaluating the success of public participation in integrated catchment management.

Recognition of the need to manage the water environment in more holistic ways has resulted in the global growth of Integrated Catchment Management (ICM). ICM is characterised by horizontal integration, encouraging interdisciplinary working between traditionally disparate management sectors, alongside vertical integration, characterised by the engagement of communities; central is the promotion of participatory governance and management decision-making. ICM has been translated into policy through, for example, the EU Water Framework Directive and at a national level by policies such as the Catchment Based Approach in England. Research exploring the implementation of these policies has reported success at a catchment level, but further research is required to explore practices of management at local level within catchments. This paper presents the findings of participatory research undertaken with a catchment partnership in the northeast of England to explore the integration of top-down policy translation with how local communities interact with management agencies at sub-catchment scale (a bottom-up perspective). The research found that supra-catchment scale drivers dominate the vertical interplay between management systems at more local levels. These drivers embed traditional practices of management, which establishes public participation as a barrier to delivery of top-down management objectives, resulting in practices that exclude communities and participatory movements at the local level. Although collaboration between agencies at the partnership scale offers a potential solution to overcoming these obstacles, the paper recommends changes to supra-catchment governance structures to encourage flexibility in developing local participatory movements as assets. Further research is necessary to develop new practices of management to integrate local people more effectively into the management process.

Impact of HIV/AIDS on life expectancy in the United States.

OBJECTIVES: The potential gains in life expectancy of the US population by the partial and total elimination of deaths from HIV/AIDS were compared with that of deaths from heart disease and malignant neoplasms. METHODS: The data from the 1992 advanced mortality report and detailed information provided by the National Center for Health Statistics were analysed by using the partial multiple decrement life-table technique. RESULTS: For the total population of the United States in 1992, the gains in future life expectancy through the elimination of deaths from HIV/AIDS, heart disease and malignant neoplasms were 0.34, 3.25 and 3.21 years, respectively. The gains in life expectancy in those of working age 15-64 years) through the elimination of deaths from these three causes of deaths were 0.20, 0.40 and 0.55 years, respectively. Race/sex-specific calculations indicate that the total elimination of deaths from HIV/AIDS, heart disease and malignant neoplasms in white men of working age resulted in increased life expectancy of 0.28, 0.54 and 0.53, respectively, whereas the corresponding figures for black men were 0.82, 0.90 and 0.76 years, respectively. Although the impact of the elimination of the other causes remained relatively stable from 1987 to 1992, the potential gains in life expectancy for black men of working age by eliminating HIV/AIDS rose from 0.36 years in 1987 to 0.82 years in 1992. For the total US population of working age, the elimination of HIV/AIDS deaths resulted in increased life expectancy similar to that observed for a 50% reduction of heart disease or malignant neoplasms, whereas among black men of working age, the increased years of life expectancy from the elimination of HIV/AIDS deaths were virtually the same as those observed for the elimination of heart disease or malignant neoplasms. CONCLUSIONS: The potential gains in life expectancy by reduction of deaths from heart disease and malignant neoplasms are more heavily influenced by increasing years after the working ages (15-64 years), whereas the potential gains in life expectancy by reducing deaths from HIV/AIDS make a greater contribution to those of working age. Hence, in terms of the economic costs and benefits, these results indicate that in evaluating policy issues regarding allocation of research funds, studies of life expectancy are far more important than the simple approach which allocates funds on the basis of the number of deaths due to various diseases.

Reserpine and breast cancer in the Hypertension Detection and Follow-Up Program.

Recent reports on the efficacy of pharmacological management in reducing mortality associated with mild hypertension have enhanced the importance of increasing our knowledge about drug toxicity. The Hypertension Detection and Follow-Up Program (HDFP) provides a convenient setting in which to examine the association reported between reserpine usage and breast cancer. In the intensively treated and followed group (Stepped Care [SC]), the relative breast cancer experience of those who did take reserpine and those who did not was examined. Of 2529 females in SC, 1036 received reserpine, with an average exposure of 1.97 years during 5 years of follow-up. Through extensive investigation, 21 cases of breast cancer were identified. using a life table regression method of analysis to adjust for actual time of reserpine exposure, race, sex, and medication status at entry, and comparing those who took reserpine with those who did not, the author's calculated a risk ratio of 1.28, with a confidence interval of 0.58 to 2.80. Adjustment for a number of other variables known to have relationships to breast cancer did not appreciably change the results. Thus, with certain precautions, the authors conclude that in this setting there is no indication of the recently postulated association of reserpine and the short-term enhancement of breast tumor growth.

Interobserver agreement for grating acuity and letter acuity assessment in 1- to 5.5-year-olds with severe retinopathy of prematurity.

PURPOSE: To evaluate interobserver test-retest reliability of the Teller Acuity Card procedure for assessment of grating acuity at ages 1, 2, 3.5, 4.5, and 5.5 years, for HOTV letter acuity at 3.5 and 4.5 years, and for Early-Treatment Diabetic Retinopathy Study (ETDRS) letter acuity at 5.5 years in the multicenter study of Cryotherapy for Retinopathy of Prematurity (CRYO-ROP). METHODS: Subjects were the 73 participants in the CRYO-ROP study who had acuity assessed at one or more ages by two of the seven study visual acuity testers as part of a quality control procedure. All subjects had birth weights of less than 1251 g, and all had severe (threshold) ROP in one or both eyes. RESULTS: For sighted eyes, interobserver agreement for grating acuity (across all five test ages) was 0.5 octave or better in 57% of eyes and 1.0 octave or better in 85% of eyes. Interobserver agreement for letter acuity (3.5-, 4.5-, and 5.5-year test ages) was 0.5 octave or better in 71% of eyes and 1.0 octave or better in 93% of eyes. For all eyes (sighted and blind), Kendall rank correlation coefficients (Tau) were 0.86, 0.83, and 0.94 for grating, HOTV, and ETDRS acuity, respectively. Kappa statistics on data from all eyes indicated excellent interobserver agreement for grating, HOTV, and ETDRS acuity (0.73, 0.80, and 0.84, respectively). Interobserver agreement was not related to age or to severity of retinal residua of ROP. CONCLUSIONS: Excellent interobserver agreement for grating acuity measurements and for letter acuity measurements was obtained. Results suggest that with careful training and implementation of quality control procedures, high reliability of visual acuity results is possible in clinical populations of young children.

Agreement between grating acuity at age 1 year and Snellen acuity at age 5.5 years in the preterm child. Cryotherapy for Retinopathy of Prematurity Cooperative Group.

PURPOSE: To examine the relation between grating acuity at age 1 year and Snellen acuity and grating acuity at 5.5 years, in preterm children with birth weights less than 1251 g. METHODS: Subjects were participants in the multicenter study of Cryotherapy for Retinopathy of Prematurity. The Teller acuity card (TAC; Vistech Consultants, Dayton, OH) procedure was used to measure monocular grating acuity in children at ages 1 and 5.5 years. Early-treatment diabetic retinopathy study (ETDRS) charts were used to measure the childrens' monocular recognition (Snellen) acuity at age 5.5 years. Data are presented for 575 eyes with measurable TAC grating acuity at 1 year and 111 eyes that had no measurable acuity at 1 year. RESULTS: Among eyes with normal acuity at 1 year, 86.8% showed normal Snellen acuity, and 94.3% showed normal grating acuity at 5.5 years. Among eyes that were blind (i.e., had no measurable TAC grating acuity) at 1 year, 96.8% showed no quantifiable Snellen acuity, and 89.2% showed no quantifiable grating acuity at 5.5 years. Only 2.4% of eyes had acuity in the range between normal and blind at 1 year (i.e., measurable grating acuity <1.6 cyc/deg); thus, the predictive value of acuity scores in this range could not be determined. Correlation analysis indicated that the relative position within the normal range of an eye's grating acuity score at 1 year was not predictive of the relative position within the normal range of that eye's acuity score at 5.5 years. CONCLUSIONS: Among a large population of low-birth-weight infants, eyes with normal grating acuity at age 1 year generally showed normal Snellen and grating acuity at age 5.5 years, and eyes that had no quantifiable acuity at 1 year remained blind at 5.5 years. Relative position of an eye's acuity score within the normal range was not predictive of the relative position of that eye's later acuity score.

Color vision measured with pseudoisochromatic plates at five-and-a-half years in eyes of children from the CRYO-ROP study.

PURPOSE: To investigate the prevalence of color deficits at age 5 1/2 years in preterm children with birth weights of less than 1251 g who participated in the multicenter Cryotherapy for Retinopathy of Prematurity (CRYO-ROP) study. METHODS: Two cohorts of CRYO-ROP participants served as subjects: 1055 children who participated in a long-term study of the natural history of ROP at 5 of the 23 CRYO-ROP centers, and 187 children (from all 23 study centers) who had threshold ROP in both eyes and who were randomized to receive cryotherapy in 1 eye. Monocular color vision was tested at age 5 1/2 years, using the Standard Pseudoisochromatic Plates, part 2 (SPP2) for acquired color vision defects. RESULTS: In the Natural History cohort, prevalence of red-green (R-G) color deficits was 6.6% for males and 1.0% for females, similar to that of the general adult population. Prevalence of blue-yellow (B-Y) color deficits was 2.8% for males and 2.2% for females, more than 200 times that in the general adult population. Prevalence of B-Y deficits was not related to birth weight, gestational age, acute-phase ROP, optic atrophy, or retinal residua of ROP, but was related to visual acuity. In the Threshold ROP cohort, color vision deficits were no more likely in eyes that had received cryotherapy than in control eyes. CONCLUSIONS: The results confirm an increased prevalence of B-Y deficits in children born before term, and provide evidence that the increased prevalence is not related to birth weight, gestational age, or severity of ROP within this group of preterm children. No evidence was found to indicate that cryotherapy increased the rate of color vision deficits in eyes with threshold ROP.

Data monitoring in clinical trials: the case for stochastic curtailment.

Interim analyses have become an essential part of the monitoring process of clinical trials. Stochastic curtailment has been used in such analyses. This procedure allows for calculation of the probability of rejecting the null hypothesis at the end of a trial given the current data and assuming the null or an alternative hypothesis for the remainder of the trial. Such information can be used to decide whether a trial should continue or be stopped early due to either treatment benefit or harm or because of lack of power to show an effect. Using stochastic curtailment, stopping rules for one- or two-sided test trials can be easily visualized by constructing boundaries based on the null and alternative hypotheses. Interim Z test statistics falling above or below these boundaries can aid in interim monitoring decisions. Methods for constructing boundaries, expected trial times and examples of clinical trials in cardiovascular and vision research where stochastic curtailment was used are presented.

Potential gains in life expectancy or years of potential life lost: impact of competing risks of death.

BACKGROUND: Measuring the impact of competing risks of death on society is important for setting public health policy and allocating resources. However, various indicators may result in inconsistent conclusions. The potential gains in life expectancy (PGLE) by elimination of deaths from HIV/AIDS, diseases of the heart and malignant neoplasms were compared to the years of potential life lost (YPLL) due to these causes in measuring the impact of premature death for the US population of working age (15-64 years). METHODS: The PGLE and the YPLL were computed from mortality reports (1987-1992) by race and gender group for deaths from HIV/AIDS, diseases of the heart and malignant neoplasms for the US population of working age. RESULTS: The YPLL overestimated the importance of premature deaths from HIV/AIDS compared to the PGLE. For the total US population and total US white population of working age, the YPLL were about 20-30% higher than the PGLE. However, the YPLL were about 20-30% lower than the PGLE for the US black population of working age. Furthermore the relative importance of the impact of death from various diseases may be interchanged by these two indicators. For example, for US black males of working age, the impact of deaths from HIV/AIDS by PGLE in 1992 was higher than that from malignant neoplasms and lower than that from diseases of the heart, but by using YPLL, the impact of premature deaths from HIV/AIDS was higher than that from both diseases of the heart and malignant neoplasms. CONCLUSIONS: The PGLE by elimination of deaths from diseases takes into account the competing risks on the population and it can be compared easily across populations. The YPLL is an index that does not take into account competing risks and it is also heavily influenced by the age structure and total population size. Although there are several standardization techniques proposed to improve the comparability of the YPLL across different populations, the YPLL fails to address the central issue of competing risks operating on the population. For this reason, we prefer the PGLE to the YPLL in measuring the impact of premature deaths on a population.

Standardized mortality ratio and life expectancy: a comparative study of Chinese mortality.

BACKGROUND: Various models have been proposed for rapid conversion of the standardized mortality ratio (SMR) to life expectancy using data from developed countries. METHODS: We compared two methods for converting the SMR to life expectancy using mortality data from the largest developing country, China. RESULTS: The first model, using the Gompertz function, does not provide a good fit to the life expectancy and SMR of China. The regression lines derived from the second, a log-linear model using parameters estimated from the US white population are not a good fit to Chinese males and older females. However, if the parameters in the log-linear model are estimated using Chinese mortality data, the resultant regression lines fit the data reasonably well. CONCLUSION: The relationship between life expectancy and SMR based on mortality data from developed countries may not be valid for developing countries. Based on our empirical study, separate estimates of the coefficients of the model are required for developing countries.

Leg and trunk length at 43 years in relation to childhood health, diet and family circumstances; evidence from the 1946 national birth cohort.

BACKGROUND: This is a study of the associations of adult leg and trunk length with early life height and weight, diet, socioeconomic circumstances, and health, and parental height, divorce and death. METHOD: The data used were collected in a longitudinal study of the health, development and ageing of a British national birth cohort (N = 2879 in this analysis) studied since birth in 1946. Multiple regression models were used to investigate the relationships. RESULTS: Adult leg and trunk length were each positively associated with parental height, birthweight, and weight at 4 years. Leg length was associated positively with breastfeeding and energy intake at 4 years. Trunk length was associated negatively with serious illness in childhood and possibly also parental divorce, but not with the dietary data. CONCLUSION: Adult leg length is particularly sensitive to environmental factors and diet in early childhood because that is the period of most rapid leg growth. Trunk growth is faster than leg growth after infancy and before puberty, and may be associated with the effects of serious illness and parental separation because of the child's growing sensitivity to stressful circumstances, as well as the result of the biological effects of illness.

Correlation of retinopathy of prematurity in fellow eyes in the cryotherapy for retinopathy of prematurity study. The Cryotherapy for Retinopathy of Prematurity Cooperative Group.

OBJECTIVE: To examine the similarity of extent (sectors) and severity (stage) of acute-phase retinopathy of prematurity (ROP) between fellow eyes and the concordance of cicatricial outcomes at age 1 year of eyes that did not develop threshold disease. METHODS: Four thousand ninety-nine infants with birth weights of less than 1251 g who participated in a natural history segment of the Cryotherapy for Retinopathy study underwent biweekly eye examinations from 4 to 6 weeks after birth until retinal vasculature was complete or until ROP regressed or reached threshold severity. Eyes were categorized as follows: (1) no ROP, (2) less than prethreshold ROP, (3) prethreshold ROP, (4) threshold ROP, and (5) unable to determine. The presence and stage of ROP residua in fellow eyes were evaluated at 12 months. RESULTS: Acute-phase ROP status between 32 and 42 weeks postconceptional age showed a high degree of correspondence between fellow eyes in severity (stage) and location (zone) of ROP, presence of plus disease, and sectors of stage 3 retinopathy. More variability between eyes was seen when cicatricial status at age 1 year was examined. This higher variability was evident even though results from patients with threshold ROP (many of whom underwent cryotherapy) were excluded. CONCLUSION: The usual course of ROP during its acute phase is for fellow eyes to be very similar in ROP status. However, asymmetry between eyes is not unusual in eyes with posterior pole residua of ROP.

Surfactant prophylaxis and retinopathy of prematurity.

OBJECTIVE: The use of exogenous surfactant has led to a decrease in mortality of low-birth-weight infants. In some instances, use of this drug has also led to a reduction in neonatal morbidity, such as respiratory distress syndrome. This study was undertaken to determine whether prophylactic surfactant therapy has an effect on the incidence and severity of retinopathy of prematurity. DESIGN: The authors reviewed the findings of sequential prospective ophthalmologic examinations performed in two neonatal intensive care units that participated in randomized trials of prophylactic exogenous mammalian surfactant. PATIENTS: There were 43 patients in the control group (no prophylactic surfactant) and 43 patients in the prophylactic surfactant group. These groups did not differ on the basis of birth weight, gestational age, race, or gender. RESULTS: The incidence and severity of retinopathy of prematurity did not vary between the control and surfactant-treated infants. Only birth weight appeared to be significantly related to the incidence and severity of retinopathy of prematurity. CONCLUSIONS: These results suggest that the widespread use of prophylactic surfactant therapy will not change the incidence of retinopathy of prematurity in extremely low-birth-weight infants. However, the absolute number of affected patients will likely increase because of the decrease in mortality of extremely low-birth-weight patients, the patients most at risk for retinopathy of prematurity.

Partial retinal detachment at 3 months after threshold retinopathy of prematurity. Long-term structural and functional outcome. Multicenter Trial of Cryotherapy for Retinopathy of Prematurity Cooperative Group.

OBJECTIVE: To investigate the structural and functional outcome at age 4 1/2 years of eyes that had partial retinal detachment (RD) at 3 months after the occurrence of threshold retinopathy of prematurity; these eyes were involved in the Multicenter Trial of Cryotherapy for Retinopathy of Prematurity study. METHODS: Of the 531 eyes in the randomized portion of the Multicenter Trial of Cryotherapy for Retinopathy of Prematurity study, 61 had partial RD at the 3-month examination. The extent of retinal involvement was recorded, and the presence of a foveal detachment was noted. At the examination conducted at age 4 1/2 years, the fundus structure was graded into cicatricial retinopathy of prematurity outcome categories by study ophthalmologists, and the visual acuity was measured by masked examiners using the Teller Acuity Card procedure and the crowded HOTV recognition acuity test. RESULTS: Of the 61 eyes, 7 eyes continued to have partial RD at age 4 1/2 years. Of the remaining eyes, 20 eyes had structural outcomes classified as favorable in the Multicenter Trial of Cryotherapy for Retinopathy of Prematurity study, and 27 eyes had unfavorable structural outcomes. Data were unrecordable for 3 eyes and missing for 4 eyes. No difference in outcome was found for eyes with partial RD at 3 months that had undergone cryotherapy vs eyes that had served as controls. Only 6 eyes had a visual acuity better than 20/200. When partial RDs did not involve the fovea at 3 months, structural and functional outcomes at 4 1/2 years were better than when RDs involved the fovea. The best predictor of outcome was the extent of RD at 3 months. CONCLUSIONS: Partial RD present 3 months after threshold retinopathy of prematurity is unstable anatomically, and the visual outcome is generally poor. Structure and function at 4 1/2 years are related to the extent of RD and the involvement of the fovea at 3 months.

Strabismus in premature infants in the first year of life. Cryotherapy for Retinopathy of Prematurity Cooperative Group.

OBJECTIVES: To present the 3- and 12-month strabismus data from 3030 premature infants with birth weights less than 1251 g enrolled in the Multicenter Trial of Cryotherapy for Retinopathy of Prematurity. DESIGN: Data from the 3- and 12-month examinations conducted at 23 regional study centers were tabulated for all infants. The main outcome measure, ocular motility, was compared with baseline demographic variables and retinopathy of prematurity severity for the worse eye. Findings at 3 months were compared with the incidence of strabismus at 12 months. RESULTS: At 3 months, 200 (6.6%) of the 3030 infants were strabismic. In the 2449 infants examined at both time points, 289 (11.8%) were found to have strabismus at 12 months. Retinopathy of prematurity was significant for strabismus at both 3 and 12 months (P<.001). The presence of strabismus at 3 months was found to be a highly significant predictor of strabismus at 12 months. Anisometropia, abnormal fixation, and unfavorable retinal structure also were significant predictors of strabismus at 1 year. The total prevalence of strabismus in the first year of life was 14.7%. CONCLUSION: The presence of acute-phase retinopathy of prematurity places the premature infant at increased risk for strabismus.

Racial variation in retinopathy of prematurity. The Cryotherapy for Retinopathy of Prematurity Cooperative Group.

OBJECTIVES: To determine and compare the incidence of severe, vision-threatening retinopathy of prematurity (ROP) in black and white low-birth-weight infants. DESIGN: Prospective cohort study. SETTING: Seventy neonatal intensive care units in 23 US participating centers in the Multicenter Trial of Cryotherapy for Retinopathy of Prematurity. PATIENTS: A total of 4099 premature infants weighing less than 1251 g at birth were enrolled to evaluate the natural history of ROP. This 'Natural History' cohort included 2158 white infants and 1584 black infants who were followed up prospectively according to a Natural History protocol. MAIN OUTCOME MEASURES: Incidence and severity of acute ROP. RESULTS: While ROP occurred with similar frequency in all racial subgroups, severe ROP was less common in black infants. One hundred sixty (7.4%) of 2158 white infants reached threshold ROP (defined as at least 5 contiguous or 8 cumulative clock-hours of stage 3 retinopathy in zone 1 or zone 2 in the presence of "plus disease" [dilation and tortuosity of the posterior pole blood vessels]), but only 51 (3.2%) of 1584 black infants progressed to threshold ROP. Using multiple logistic regression analysis, race emerged as a highly significant factor (P < .001) in the development of threshold disease, even when birth weight, gestational age status at delivery, sex, multiple births, and transport status were considered. CONCLUSIONS: Severe, vision-threatening ROP occurs with greater frequency in low-birth-weight white infants than in low-birth-weight black infants who are seemingly at equivalent risk. The reason for this disparity is unknown. We speculate that differences in retinal pigmentation may confer relative protection against free radical-mediated phototoxic injury in black infants.

The life course prospective design: an example of benefits and problems associated with study longevity.

Although the life course prospective study design has many benefits, and information from such studies is in increasing demand for scientific and policy purposes, it has potential inherent design problems associated with its longevity. These are in particular the fixed sample structure and the data collected in early life, which are each determined by the scientific principles of another time and the risk over time of increased sample loss and distortion through loss. The example of a national birth cohort in Britain, studied from birth so far to age 53 years is used to address these questions. Although the response rate is high, avoidable loss, which was low in childhood, increased in adulthood, and was highest in those in adverse socio-economic circumstances and those with low scores on childhood cognitive measures. Recent permanent refusal rate rises may be the result of better tracing and/or a response to increased requests for biological measurement. Nevertheless, the responding sample continues in most respects to be representative of the national population of a similar age. Consistency of response over the study's 20 data collections has been high. The size of the sample responding in adulthood is adequate for the study of the major costly diseases, and for the study of functional ageing and its precursors. This study's continuation has depended not only on scientific value but also policy relevance. Although the problems inherent in the prospective design are unavoidable they are not, in the study described, a barrier to scientific and policy value. That seems also likely in Britain's two later born national birth cohort studies that have continued into adulthood.

Outcome-based management of retinopathy of prematurity. Multicenter Trial of Cryotherapy for Retinopathy of prematurity Cooperative Group.

PURPOSE: A system is presented for sequentially computing the risk of progression of retinopathy of prematurity (ROP) for infants born weighing not more than 1250 gm. A personal computer program is used to monitor infants' risk of threshold ROP from first appearance of ROP, and the progression in severity is tracked with multiple logistic risk models developed from data in the Multicenter Trial of Cryotherapy for Retinopathy of Prematurity. METHODS: After entry of the infant's birth weight, gestational age, ethnicity, birth in the current hospital or elsewhere, single or multiple birth, and maturity zone of retinal vessels, risk of progression to threshold severity is calculated. New estimates of risk are computed at onset of ROP and prethreshold ROP (any zone I ROP, zone II stage 2+ or 3) according to the extent of retinal vascularization when ROP first appears, how rapidly ROP progresses, and how severe it is. When threshold ROP (8 total or 5 contiguous clock hours of stage 3+ in zone I or II) is reached,the system provides separate estimates of risk that the eye will have an unfavorable 3-month outcome if treated or not. RESULTS: Estimates of risk of progression to threshold disease among the 4099 patients in the Multicenter Trial of Cryotherapy for Retinopathy of Prematurity natural history study varied from less than 1% to more than 70%. For eyes with threshold disease, the risk of an unfavorable outcome at 3 months without treatment varied from less than 10% to more than 90%. CONCLUSION: This method of tracking identifies infants at high risk for severe ROP and poor structural outcome. It provides information about prognosis with a specificity heretofore impossible.

A computer program for an illness-death process with time-dependent covariates.

This paper presents a computer program for estimating transition probabilities between states in a stochastic model for an illness-death process which incorporates time-dependent covariates. Parameters are estimated by the method of maximum likelihood using the Newton-Raphson iterative procedure. The program provides the standard normal deviate statistics as well as the value of the maximum of the likelihood function which can be used on repeated applications to test hypotheses concerning coefficients associated with covariates. Although this program is demonstrated by using a model with two 'illness' states and two 'death' states, it is also suitable for analyzing data with models involving fewer states, such as the analysis of survival time with covariates assuming a proportional hazard model.

Measuring the impact of hepatitis A virus in Chinese cities: a life table approach.

The infection of hepatitis A virus is an important public health problem in China. In 1990, a survey on seroprevalence of anti-hepatitis A was conducted in eight large cities of population size between one to four million. The results were used to analyze the impact of hepatitis A. In our study, we used life table techniques to determine the impact that the hepatitis A virus (HAV) has on these eight cities by computing the expected years of life with anti-hepatitis A virus. We compared the results from our approach with those from a previous method. The expected years of life with anti-hepatitis A virus were 53.82, 54.65, 44.26, 53.89, 46.18, 55.77, 55.31 and 49.89 for the eight cities (Xi'an, Huhehaote, Chongqing, Nanjing, Jinan, Ha'erbin, Fuzhou and Nanchang), respectively. The hepatitis A virus had the greatest impact in Ha'erbin in northeastern China; whereas, the impact was lowest in Chongqing in southwestern China. However, based on the previous indicator, Chongqing was ranked the highest among these cities. Through our comparative study of the methods, our approach provides a better measure on the burden of the disease than the previous method. It also identifies subgroups of the population where the disease has its greatest impact on the population.