Basic models for disease occurrence in epidemiology

Estimating geographic variation of infection fatality ratios during epidemics

Objectives

We aim to estimate geographic variability in total numbers of infections and infection fatality ratios (IFR; the number of deaths caused by an infection per 1,000 infected people) when the availability and quality of data on disease burden are limited during an epidemic.

Methods

We develop a noncentral hypergeometric framework that accounts for differential probabilities of positive tests and reflects the fact that symptomatic people are more likely to seek testing. We demonstrate the robustness, accuracy, and precision of this framework, and apply it to the United States (U.S.) COVID-19 pandemic to estimate county-level SARS-CoV-2 IFRs.

Results

The estimators for the numbers of infections and IFRs showed high accuracy and precision; for instance, when applied to simulated validation data sets, across counties, Pearson correlation coefficients between estimator means and true values were 0.996 and 0.928, respectively, and they showed strong robustness to model misspecification. Applying the county-level estimators to the real, unsimulated COVID-19 data spanning April 1, 2020 to September 30, 2020 from across the U.S., we found that IFRs varied from 0 to 44.69, with a standard deviation of 3.55 and a median of 2.14.

Conclusions

The proposed estimation framework can be used to identify geographic variation in IFRs across settings.

Systematic description of COVID-19 pandemic using exact SIR solutions and Gumbel distributions

An epidemiological study is carried out in several countries analyzing the first wave of the COVID-19 pandemic using the SIR model and Gumbel distribution. The equations of the SIR model are solved exactly using the proper time as a parameter. The physical time is obtained by integration of the inverse of the infected function over proper time. Some properties of the solutions of the SIR model are studied such as time scaling and the asymmetry, which allows to obtain the basic reproduction number from the data. Approximations to the solutions of the SIR model are studied using Gumbel distributions by least squares fit or by adjusting the maximum of the infected function. Finally, the parameters of the SIR model and the Gumbel function are extracted from the death data and compared for the different countries. It is found that ten of the selected countries are very well described by the solutions of the SIR model, with a basic reproduction number between 3 and 8.

Acceptance of Different Self-sampling Methods for Semiweekly SARS-CoV-2 Testing in Asymptomatic Children and Childcare Workers at German Day Care Centers: A Nonrandomized Controlled Trial

IMPORTANCE

Closure of day care centers (DCCs) to contain the COVID-19 pandemic has been associated with negative effects on children's health and well-being.

OBJECTIVE

To investigate the acceptance of self-sampling methods for continuous SARS-CoV-2 surveillance among asymptomatic children and childcare workers (CCWs) in DCCs.

DESIGN, SETTING, AND PARTICIPANTS

This nonrandomized pilot study included children and CCWs at 9 DCCs in Wuerzburg, Germany, from May to July 2021.

INTERVENTIONS

Twice weekly testing for SARS-CoV-2 was conducted by self-sampled mouth-rinsing fluid (saliva sampling [SAL], with subsequent pooled polymerase chain reaction test) plus nasal rapid antigen self-test (RAgT) (group 1), SAL only (group 2), or RAgT only (group 3) in children and CCWs.

MAIN OUTCOMES AND MEASURES

Main outcomes were rates for initial acceptance and successful (≥60% of scheduled samples) long-term participation. The probability of SARS-CoV-2 introduction into DCCs was modeled as a function of age-adjusted background incidence and DCC size.

RESULTS

Of 836 eligible children, 452 (54.1%; 95% CI, 50.7%-57.4%) participated (median [IQR] age: 4 [3-5] years; 213 [47.1%] girls), including 215 (47.6%) in group 1, 172 (38.1%) in group 2, and 65 (14.4%) in group 3. Of 190 CCWs, 139 (73.2%; 95% CI, 66.4%-79.0%) participated (median [IQR] age: 30 [25-46] years; 128 [92.1%] women), including 96 (69.1%) in group 1, 29 (20.9%) in group 2, and 14 (10.1%) in group 3. Overall, SARS-CoV-2 PCR tests on 5306 SAL samples and 2896 RAgTs were performed in children, with 1 asymptomatic child detected by PCR from SAL. Successful long-term participation was highest in group 2 (SAL only; children: 111 of 172 [64.5%]; CCWs: 18 of 29 [62.1%]). Weekly participation rates in children ranged from 54.0% to 83.8% for SAL and from 44.6% to 61.4% for RAgT. Participation rates decreased during the study course (P < .001). The probability of SARS-CoV-2 introduction into a DCC with 50 children was estimated to reach at most 5% for an age-adjusted SARS-CoV-2 incidence below 143.

CONCLUSIONS AND RELEVANCE

Self-sampling for continuous SARS-CoV-2 testing was well accepted, with SAL being the preferred method. Given the high number of negative tests, thresholds for initiating continuous testing should be established based on age-adjusted SARS-CoV-2 incidence rates.

TRIAL REGISTRATION

German Registry for Clinical Trials Identifier: DRKS00025546.

Impact of implementation timing on the effectiveness of stay-at-home requirement under the COVID-19 pandemic: Lessons from the Italian Case

When a new infectious outbreak emerges, governments must initially rely on non-pharmaceutical interventions (NPIs) to mitigate the impact of the pathogen. Although a strict stay-at-home requirement (i.e., lockdown) presents high effectiveness in reducing patients hospitalized in intensive care units (ICUs), it comes with unintended physical, psychological, and economic damages for the citizens. Using how Italy managed the COVID-19 outbreak from February to September 2020 on a national basis, this study aims at understanding the impact of implementation timing on the effectiveness of NPIs. Our findings may be helpful to avoid the implementation of stay-at-home requirements when it is not strictly necessary. A compartmental SEICRD model was developed to create the baseline scenario without NPIs. Generalized Poisson regressions were applied to study the change in effectiveness over-time of NPIs on Avoided ICUs for each one of the Italian regions. Our study suggests that although the stay-at-home requirement is the most effective measure in reducing ICU hospitalizations in regions encountering the outbreak early, its effectiveness decreases in regions encountering the outbreak later, where a set of other NPIs are more effective. We developed a reference of daily new cases when lockdown should be implemented or avoided, accordingly. Our findings could be useful to support policymakers in contrasting the pandemic and in limiting the societal and economic impact of stringent NPIs.

Monte Carlo simulation of COVID-19 pandemic using Planck’s probability distribution

We present a Monte Carlo simulation model of an epidemic spread inspired on physics variables such as temperature, cross section and interaction range, which considers the Plank distribution of photons in the black body radiation to describe the mobility of individuals. The model consists of a lattice of cells that can be in four different states: susceptible, infected, recovered or death. An infected cell can transmit the disease to any other susceptible cell within some random range R. The transmission mechanism follows the physics laws for the interaction between a particle and a target. Each infected particle affects the interaction region a number n of times, according to its energy. The number of interactions is proportional to the interaction cross section σ and to the target surface density ρ. The discrete energy follows a Planck distribution law, which depends on the temperature T of the system. For any interaction, infection, recovery and death probabilities are applied. We investigate the results of viral transmission for different sets of parameters and compare them with available COVID-19 data. The parameters of the model can be made time dependent in order to consider, for instance, the effects of lockdown in the middle of the pandemic.

Longitudinal Projection of Herd Prevalence of Influenza A(H1N1)pdm09 Virus Infection in the Norwegian Pig Population by Discrete-Time Markov Chain Modelling

In order to quantify projections of disease burden and to prioritise disease control strategies in the animal population, good mathematical modelling of infectious disease dynamics is required. This article investigates the suitability of discrete-time Markov chain (DTMC) as one such model for forecasting disease burden in the Norwegian pig population after the incursion of influenza A(H1N1)pdm09 virus (H1N1pdm09) in Norwegian pigs in 2009. By the year-end, Norway's active surveillance further detected 20 positive herds from 54 random pig herds, giving an estimated initial population prevalence of 37% (95% CI 25-52). Since then, Norway's yearly surveillance of pig herd prevalence has given this study 11 years of data from 2009 to 2020 to work with. Longitudinally, the pig herd prevalence for H1N1pdm09 rose sharply to >40% in three years and then fluctuated narrowly between 48% and 49% for 6 years before declining. This initial longitudinal pattern in herd prevalence from 2009 to 2016 inspired this study to of test the steady-state discrete-time Markov chain model in forecasting disease prevalence. With the pig herd as the unit of analysis, the parameters for DTMC came from the initial two years of surveillance data after the outbreak, namely vector prevalence, first herd incidence and recovery rates. The latter two probabilities formed the fixed probability transition matrix for use in a discrete-time Markov chain (DTMC) that is quite similar to another compartmental model, the susceptible-infected-susceptible (SIS) model. These DTMC of predicted prevalence (DTMCP) showed good congruence (Pearson correlation = 0.88) with the subsequently observed herd prevalence for seven years from 2010 to 2016. While the DTMCP converged to the stationary (endemic) state of 48% in 2012, after three time steps, the observed prevalence declined instead from 48% after 2016 to 25% in 2018 before rising to 29% in 2020. A sudden plunge in H1N1pdm09 prevalence amongst Norwegians during the 2016/2017 human flu season may have had a knock-on effect in reducing the force of infection in pig herds in Norway. This paper endeavours to present the discrete-time Markov chain (DTMC) as a feasible but limited tool in forecasting the sequence of a predicted infectious disease's prevalence after it's incursion as an exotic disease.

Effects of climate changes and road exposure on the rapidly rising legionellosis incidence rates in the United States

Legionellosis is an infection acquired through inhalation of aerosols that are contaminated with environmental bacteria Legionella spp. The bacteria require warm temperature for proliferation in bodies of water and moist soil. The legionellosis incidence in the United States has been rising rapidly in the past two decades without a clear explanation. In the meantime, the US has recorded consecutive years of above-norm temperature since 1997 and precipitation surplus since 2008. The present study analyzed the legionellosis incidence in the US during the 20-year period of 1999 to 2018 and correlated with concurrent temperature, precipitation, solar ultraviolet B (UVB) radiation, and vehicle mileage data. The age-adjusted legionellosis incidence rates rose exponentially from 0.40/100,000 in 1999 (with 1108 cases) to 2.69/100,000 in 2018 (with 9933 cases) at a calculated annual increase of 110%. In regression analyses, the rise correlated with an increase in vehicle miles driven and with temperature and precipitation levels that have been above the 1901–2000 mean since 1997 and 2008, respectively, suggesting more road exposure to traffic-generated aerosols and promotive effects of anomalous climate. Remarkably, the regressions with cumulative anomalies of temperature and precipitation were robust (R² ≥ 0.9145, P ≤ 4.7E-11), implying possible changes to microbial ecology in the terrestrial and aquatic environments. An interactive synergy between annual precipitation and vehicle miles was also found in multiple regressions. Meanwhile, the bactericidal UVB radiation has been decreasing, which also contributed to the rising incidence in an inverse correlation. The 2018 legionellosis incidence peak corresponded to cumulative effects of the climate anomalies, vast vehicle miles (3,240 billion miles, 15904 km per capita), record high precipitation (880.1 mm), near record low UVB radiation (7488 kJ/m²), and continued above-norm temperature (11.96°C). These effects were examined and demonstrated in California, Florida, New Jersey, Ohio, and Wisconsin, states that represent diverse incidence rates and climates. The incidence and above-norm temperature both rose most in cold Wisconsin. These results suggest that warming temperature and precipitation surplus have likely elevated the density of Legionella bacteria in the environment, and together with road exposure explain the rapidly rising incidence of legionellosis in the United States. These trends are expected to continue, warranting further research and efforts to prevent infection.

Global analysis of the COVID-19 pandemic using simple epidemiological models

Several analytical models have been developed in this work to describe the evolution of fatalities arising from coronavirus COVID-19 worldwide. The Death or 'D' model is a simplified version of the well-known SIR (susceptible-infected-recovered) compartment model, which allows for the transmission-dynamics equations to be solved analytically by assuming no recovery during the pandemic. By fitting to available data, the D-model provides a precise way to characterize the exponential and normal phases of the pandemic evolution, and it can be extended to describe additional spatial-time effects such as the release of lockdown measures. More accurate calculations using the extended SIR or ESIR model, which includes recovery, and more sophisticated Monte Carlo grid simulations - also developed in this work - predict similar trends and suggest a common pandemic evolution with universal parameters. The evolution of the COVID-19 pandemic in several countries shows the typical behavior in concord with our model trends, characterized by a rapid increase of death cases followed by a slow decline, typically asymmetric with respect to the pandemic peak. The fact that the D and ESIR models predict similar results - without and with recovery, respectively - indicates that COVID-19 is a highly contagious virus, but that most people become asymptomatic (D model) and eventually recover (ESIR model).

Emergency medical services and cardiac arrest from drug overdose: a protocol for a systematic review of incidence and survival outcomes

REVIEW QUESTION

The primary review question is: what is the global incidence rate of emergency medical services (EMS)-attended and EMS-treated out-of-hospital cardiac arrest (OHCA) precipitated by drug overdose in adults?The secondary review questions are: what proportion of adults with EMS-treated overdose OHCA: i) survived to hospital discharge or 30 days, ii) survived with intact neurological function at hospital discharge (i.e. Cerebral Performance Category or modified Rankin Scale ≤ 2), iii) achieved prehospital return of spontaneous circulation, iv) survived to hospital, and v) survived to 12 months?

Interstitial Lung Disease in Relatives of Patients with Pulmonary Fibrosis

Rationale: Although relatives of patients with familial pulmonary fibrosis (FPF) are at an increased risk for interstitial lung disease (ILD), the risk among relatives of sporadic idiopathic pulmonary fibrosis (IPF) is not known.Objectives: To identify the prevalence of interstitial lung abnormalities (ILA) and ILD among relatives of patients with FPF and sporadic IPF.Methods: Undiagnosed first-degree relatives of patients with pulmonary fibrosis (PF) consented to participate in a screening study that included the completion of questionnaires, pulmonary function testing, chest computed tomography, a blood sample collection for immunophenotyping, telomere length assessments, and genetic testing.Measurements and Main Results: Of the 105 relatives in the study, 33 (31%) had ILA, whereas 72 (69%) were either indeterminate or had no ILA. Of the 33 relatives with ILA, 19 (58%) had further evidence for ILD (defined by the combination of imaging findings and pulmonary function testing decrements). There was no evidence in multivariable analyses that the prevalence of either ILA or ILD differed between the 46 relatives with FPF and the 59 relatives with sporadic IPF. Relatives with decrements in either total lung or diffusion capacity had a greater than 9-fold increase in their odds of having ILA (odds ratio, 9.6; 95% confidence interval, 3.1-29.8; P < 0.001).Conclusions: An undiagnosed form of ILD may be present in greater than 1 in 6 older first-degree relatives of patients with PF. First-degree relatives of patients with both familial and sporadic IPF appear to be at similar risk. Our findings suggest that screening for PF in relatives might be warranted.

Epidemiology, Clinical Features, and Use of Early Supportive Measures in PHACE Syndrome: A European Multinational Observational Study

BACKGROUND

PHACE syndrome is a rare inborn condition characterized by large facial hemangiomas and variable malformations of the arterial system, heart, central nervous system, and eyes. According to Orphanet estimates, the prevalence is <1.0 per million. Data from Europe are limited to small case series, and there are no population-based data available.

OBJECTIVES

We conducted the present study to provide population-based estimates of the disease prevalence of PHACE syndrome in children in Germany, Switzerland, and Austria. We compared these first systematic data on PHACE syndrome from Europe to published data from the PHACE Syndrome International Clinical Registry and Genetic Repository (USA). Clinical features in our cohort with PHACE syndrome were assessed in detail, including the need for early supportive measures.

METHODS

We used a population-based approach by means of a previously well-established network of child neurologists from Germany, Switzerland, and Austria ("ESNEK") to identify potential patients. The patients' guardians and child neurologists were asked to fill in questionnaires developed in collaboration with the International PHACE Registry.

RESULTS

We identified 19 patients with PHACE syndrome. Estimated prevalence rates were 6.5 per million in Switzerland, 0.59 per million in Germany, and 0.65 per million in Austria. A subset of 10 patients from Germany and Switzerland participated in our study, providing detailed clinical assessment (median age: 2.5 years; 9 females, 1 male). Cerebrovascular involvement was frequent (80%). Facial hemangioma extent correlated significantly with the number of organs involved (p = 0.011). In 9 out of 10 patients, facial hemangiomas were treated successfully with oral propranolol. Baseline demographic data as well as the rate of cerebrovascular and cardiovascular anomalies were in line with those from the US International PHACE Registry and other published PHACE cohorts.

CONCLUSIONS

Our study provides population-based estimates for PHACE syndrome in 3 German-speaking countries. The data from Switzerland indicate that PHACE syndrome may be more prevalent than demonstrated by previous reports. Underreporting of PHACE syndrome in Germany and Austria likely accounts for the differences in prevalence rates. The clinical observation of a potential association between the size of facial hemangioma and extent of organ involvement warrants further investigation.

Association of Migraine With Aura and Other Risk Factors With Incident Cardiovascular Disease in Women

IMPORTANCE

Migraine with aura is known to increase the risk of cardiovascular disease (CVD). The absolute contribution of migraine with aura to CVD incidence in relation to other CVD risk factors remains unclear.

OBJECTIVE

To estimate the CVD incidence rate for women with migraine with aura relative to women with other major vascular risk factors.

DESIGN, SETTING, AND PARTICIPANTS

Female health professionals in the US (the Women's Health Study cohort) with lipid measurements and no CVD at baseline (1992-1995) were followed up through December 31, 2018.

EXPOSURES

Self-reported migraine with aura compared with migraine without aura or no migraine at baseline.

MAIN OUTCOMES AND MEASURES

The primary outcome was major CVD (first myocardial infarction, stroke, or CVD death). Generalized modeling procedures were used to calculate multivariable-adjusted incidence rates for major CVD events by risk factor status that included all women in the cohort.

RESULTS

The study population included 27 858 women (mean [SD] age at baseline, 54.7 [7.1] years), among whom 1435 (5.2%) had migraine with aura and 26 423 (94.8%) did not (2177 [7.8%] had migraine without aura and 24 246 [87.0%] had no migraine in the year prior to baseline). During a mean follow-up of 22.6 years (629 353 person-years), 1666 major CVD events occurred. The adjusted incidence rate of major CVD per 1000 person-years was 3.36 (95% CI, 2.72-3.99) for women with migraine with aura vs 2.11 (95% CI, 1.98-2.24) for women with migraine without aura or no migraine (P < .001). The incidence rate for women with migraine with aura was significantly higher than the adjusted incidence rate among women with obesity (2.29 [95% CI, 2.02-2.56]), high triglycerides (2.67 [95% CI, 2.38-2.95]), or low high-density lipoprotein cholesterol (2.63 [95% CI, 2.33-2.94]), but was not significantly different from the rates among those with elevated systolic blood pressure (3.78 [95% CI, 2.76-4.81]), high total cholesterol (2.85 [95% CI, 2.38-3.32]), or family history of myocardial infarction (2.71 [95% CI, 2.38-3.05]). Incidence rates among women with diabetes (5.76 [95% CI, 4.68-6.84]) or who currently smoked (4.29 [95% CI, 3.79-4.79]) were significantly higher than those with migraine with aura. The incremental increase in the incidence rate for migraine with aura ranged from 1.01 additional cases per 1000 person-years when added to obesity to 2.57 additional cases per 1000 person-years when added to diabetes.

CONCLUSIONS AND RELEVANCE

In this study of female health professionals aged at least 45 years, women with migraine with aura had a higher adjusted incidence rate of CVD compared with women with migraine without aura or no migraine. The clinical importance of these findings, and whether they are generalizable beyond this study population, require further research.

Standardized Risk Analysis Approach Aimed to Evaluate the Last African Swine Fever Eradication Program Performance, in Sardinia

From more than 40 years African swine fever (ASF) is endemic in Sardinia. Historically, areas at higher risk are located throughout some inland parts of this island where domestic pigs are still illegally kept in semi-wild conditions, living in contact with the local wild boar population, thereby creating perfect conditions for disease endemicity. A new eradication plan (EP-ASF15-18) has been ongoing for the past 3 years, based on a comprehensive strategy adapted to the local situation and focused on strong actions on domestic pig farms, wild boars (WB), and the third Sardinian typical involved population [illegal free-ranging pigs (FRPs)]. A fundamental aspect of the plan is the classification of pig farms as "controlled" or "certified," based on clinical, structural, and biosecurity characteristics. The eradication plan also provides for strong action against illegal farms and pig meat marketing channels. In addition, this plan establishes specific control measures for WB hunting and ASF checks. Each control strategy is specifically based on municipality risk level, to focus actions and resources on areas at higher risk of endemic or re-emerging ASF. Thus, precise risk classification is fundamental to this goal. The aim of the present work was to establish an ASF risk index, to provide a summary measure of the risk level in the Sardinian municipalities. This synthetic measure can express the different aspects of a multidimensional phenomenon with a single numerical value, facilitating territorial and temporal comparisons. To this end, retrospective data (years 2011-2018) were used. The ASF risk index is the result of the algorithmic combination of numerical elementary indicators: disease prevalence in the suid populations, WB compliance with EP-ASF15-18, domestic pig compliance with EP-ASF15-18, and presence of FRPs. A negative binomial regression model has been applied and predictors calculated to obtain a risk index for each municipality. The result of the risk analysis was discussed and considered according to expert opinion and consensus. The results of this study, expressed as risk score and classified into five risk levels, can be used to help define actions to be carried out in each Sardinian municipality, according to the risk assessment for the territory.

Incidence of autoimmune pulmonary alveolar proteinosis estimated using Poisson distribution

The incidence and prevalence of autoimmune pulmonary alveolar proteinosis in Japan were previously estimated to be 0.49 and 6.2 per million, respectively. Thereafter, an increase in serological diagnosis forced a re-estimation of the incidence based on more contemporaneous data using more robust methods.

Sera of 702 patients were positive for granulocyte-macrophage colony-stimulating factor autoantibody during the 2006–2016 period (group A). Of these patients, 43 were actively surveyed in Niigata prefecture (group B) for estimation of the incidence. To estimate the survival period, 103 patients (group C) were investigated retrospectively for the 1999–2017 period using restricted mean survival time.

In group A, the number of patients diagnosed in each prefecture was closely correlated with the corresponding population, indicating no regional integration of onset. In group B, a total of 43 patients were diagnosed, the annual number followed a Poisson distribution and the incidence was thus estimated to be 1.65 per million. In group C, the retrospective cohort study revealed the mean survival period to be 16.1 years. Taken together, the prevalence was estimated to be 26.6 per million, indicating that the previous data for incidence and prevalence was an underestimation.

The latest epidemiologic study of autoimmune pulmonary alveolar proteinosis revealed the incidence and prevalence, estimated using Poisson distribution, to be 1.65 and 26.6 per million, respectivelyhttp://ow.ly/Wyyd30n4IYP

Calibrating Parameters for Microsimulation Disease Models: A Review and Comparison of Different Goodness-of-Fit Criteria

BACKGROUND

Calibration (estimation of model parameters) compares model outcomes with observed outcomes and explores possible model parameter values to identify the set of values that provides the best fit to the data. The goodness-of-fit (GOF) criterion quantifies the difference between model and observed outcomes. There is no consensus on the most appropriate GOF criterion, because a direct performance comparison of GOF criteria in model calibration is lacking.

METHODS

We systematically compared the performance of commonly used GOF criteria (sum of squared errors [SSE], Pearson chi-square, and a likelihood-based approach [Poisson and/or binomial deviance functions]) in the calibration of selected parameters of the MISCAN-Colon microsimulation model for colorectal cancer. The performance of each GOF criterion was assessed by comparing the 1) root mean squared prediction error (RMSPE) of the selected parameters, 2) computation time of the calibration procedure of various calibration scenarios, and 3) impact on estimated cost-effectiveness ratios.

RESULTS

The likelihood-based deviance resulted in the lowest RMSPE in 4 of 6 calibration scenarios and was close to best in the other 2. The SSE had a 25 times higher RMSPE in a scenario with considerable differences in the values of observed outcomes, whereas the Pearson chi-square had a 60 times higher RMSPE in a scenario with multiple studies measuring the same outcome. In all scenarios, the SSE required the most computation time. The likelihood-based approach estimated the cost-effectiveness ratio most accurately (up to -0.15% relative difference versus 0.44% [SSE] and 13% [Pearson chi-square]).

CONCLUSIONS

The likelihood-based deviance criteria lead to accurate estimation of parameters under various circumstances. These criteria are recommended for calibration in microsimulation disease models in contrast with other commonly used criteria.

Type I diabetes in paediatric age in Apulia (Italy): Incidence and associations with outdoor air pollutants

AIM

This study aimed to explore Type 1 diabetes (T1D) incidence and possible relations with specific air pollutants in a large population of children, during a wide time period.

METHODS

T1D rates and trends were examined (2001-2013, GAM and Joinpoint Regression analysis) by data on the first hospitalization in all children (0-14 years) living in Apulia (Southern Italy, average yearly population aged 0-14 years in the examined period: 631,275 subjects), and linked with levels of PM10, NOx, CO and ozone.

RESULTS

A total of 1501 children were first discharged in the selected area with a diagnosis of T1D. Incidence decreased from 48.5 (95% CI 43.3; 54.0, 2001) to 16.9 per 100,000 (95% CI 13.7; 20.6, 2013), with differences according to age at onset (constant at 0-4 years, continuously decreasing at 5-9 years, decreasing until 2003 at 10-14 years), and with a positive relation with PM10--but not ozone, NOx and CO average air levels. The OR was 1.037 (1.002; 1.074) in the high tertile of PM10 concentrations, and mean incidence was higher with PM10 levels in the highest, than in the medium/reference tertile. Mean age at T1D onset was linked with yearly PM10 and ozone air levels.

CONCLUSIONS

On a wide period, a stable or decreased incidence of T1D was evident in children with early- or later onset of disease, respectively. PM10 exposure significantly affects the incidence of T1D, which might be considered, at least in part, a preventable condition.

Determining the lifetime density function using a continuous approach

OBJECTIVE

To apply a continuous hazard function approach to calculate the lifetime density function (LDF) at any age, and to compare the life expectancies derived from the LDF with those obtained with standard life table (SLT) methods.

METHODS

Age-specific mortality rates were modeled through a continuous hazard function. To construct the cumulative hazard function, appropriate integration limits were considered as continuous random variables. The LDF at any age was defined on the basis of the elemental relationships with the cumulative hazard function. Life expectancies were calculated for a particular set of mortality data using the SLT approach and the expectancy of the LDF defined. APPLICATIONS AND COMPARISONS: The proposed approach was applied using mortality data from the 2001 census of Catalonia (Spain). A Gompertz function was used to model the observed age-specific mortality rates, which fitted the observed data closely. The LDF and the life expectancy, median and standard deviation of the LDF were derived using mathematical software. All differences, in percentages, between the life expectancies obtained from the two methods were 1.1% or less.

CONCLUSIONS

The LDF gives a wider interpretation of life duration, by extending a deterministic value like life expectancy to a fully informative measure like the LDF.

Maternal diet and infant leukemia: the DNA topoisomerase II inhibitor hypothesis: a report from the children's oncology group

BACKGROUND

The MLL 11q23 translocation arises in utero and is present in 75% of infant leukemias. That MLL+ acute myeloid leukemia (AML) can arise following chemotherapy with DNA topoisomerase II (DNAt2) inhibitors suggests that these substances, which also occur naturally in foods, may contribute toward infant leukemia. We hypothesized that maternal consumption of dietary DNAt2 inhibitors during pregnancy would increase the risk of infant leukemia, particularly AML(MLL+).

METHODS

This Children's Oncology Group case-control study consisted of 240 incident cases of infant acute leukemia [AML and acute lymphoblastic leukemia (ALL)] diagnosed during 1996 to 2002 and 255 random digit dialed controls. Maternal diet during pregnancy was determined through a food frequency questionnaire. An index of specific foods identified a priori to contain DNAt2 inhibitors as well as vegetables and fruits were created and analyzed using unconditional logistic regression.

RESULTS

There was little evidence of an association between the specific DNAt2 index and leukemia overall and by subtype. An exception was AML(MLL+); odds ratios (95% confidence intervals) comparing the second to fourth quartiles to the first were 1.9 (0.5-7.0), 2.1 (0.6-7.7), and 3.2 (0.9-11.9), respectively (P for trend = 0.10). For the vegetable and fruit index, there were significant or near-significant inverse linear trends for all leukemias combined, ALL(MLL+), and AML(MLL-).

CONCLUSION

Overall, maternal consumption of fresh vegetables and fruits during pregnancy was associated with a decreased risk of infant leukemia, particularly MLL+. However, for AML(MLL+) cases, maternal consumption of specific DNAt2 inhibitors seemed to increase risk. Although based on small numbers, these data provide some support for distinct etiologic pathways in infant leukemia.

Modeling diarrhea disease in children less than 5 years old

PURPOSE

Identification of the temporal pattern of diarrhea disease in children less than 5 years of age in Rio de Janeiro City (1995-1998) to provide support for decisions about prevention and control of the disease.

METHODS

The weekly counts of hospitalizations and deaths due to diarrhea disease were analyzed separately. An initial generalized linear model (GLM) was derived using variables related to weather and month. Displays of fitted generalized additive models (GAM) including a spline smoothed function of time suggested additional predictors that were used to obtain new models.

RESULTS

The initial models did not properly account for the observed cyclical pattern of the data. Graphical displays of the GAM model show a nonhomogeneous decline and annual cycles. Stepwise fitting of GLMs with two factors (cycle and season), and a time trend, showed that the full three-way interaction model was required. Plots of the residuals from the death model suggested a mixture of distributions while the residuals from the hospitalization model were approximately normal.

CONCLUSIONS

The same general pattern for both time series was found by graphical inspection and fitting of appropriate GLMs. This study provides some additional evidence that severe cases of diarrhea disease may be attributed to rotavirus.

Efficacy of permethrin-treated uniforms in combination with DEET topical repellent for protection of French military troops in Côte d'Ivoire

In 2000, 22,000 French military personnel were deployed overseas. The French military health service implemented a vector control strategy including personal protection by the use of permethrin preimpregnated battlefield uniforms (BFUs) and the application on the skin of a topical repellent (50% DEET). In 2000, French forces used an industrial process to impregnate cloth with permethrin by soaking it before cut-out of the BFU. A study was implemented in four experimental huts in Côte d'Ivoire to assess the field efficacy of the impregnated BFUs and their resistance to washing. Taking into account the systematic variations in each variable in the field and using a modeling based on logistic regression and discriminant analysis, this study showed that after 6 h without reapplication, the protective effects of the use of DEET as skin repellent was not significant, perhaps due to the high density of Anopheles mosquitoes during the night catching sessions and an average time of effective repellency of < 2 or 3 h in the field. The analysis also showed that the French process of industrial impregnation of permethrin of the BFU offered in 2000 some protection from mosquito bites but not enough to reduce significantly the incidence of malaria among nonimmune troops. No positive or negative interaction was noted when DEET and the impregnated BFUs were used together.

Childhood malnutrition and its predictors in rural Malawi

We prospectively followed up a population-based cohort of 767 rural Malawian children from birth to 36 months to characterise the timing and predictors of malnutrition. Underweight and wasting incidence peaked between 6 and 18 months of age, whereas stunting incidence was highest during the first 6 months of age. After infancy about 40% of the children were underweight, 70% stunted, and about 4% wasted. Small size during the first 3 months of life predicted the incidence of severe underweight (relative risk [95% confidence interval], 1.8 [0.9, 3.4]), severe stunting ( 2.1 [1.3, 3.4]), and moderate wasting (2.0 [1.1, 3.5]). Children with many illness episodes in infancy had a twofold risk for the development of severe underweight and moderate wasting. Severe underweight was further predicted by residence far away from a health facility and moderate wasting by maternal HIV infection. Our conclusion is that the intrauterine period and first 6 months of life are critical for the development of stunting whereas the subsequent year is more critical for the development of underweight and wasting. Strategies combating intrauterine growth retardation, maternal HIV and infant morbidity are likely to reduce the burden of malnutrition in this population.

A comparison of Campylobacter jejuni enteritis incidence rates in high- and low-poultry-density counties: Michigan 1992-1999

To compare the incidence of Campylobacter jejuni enteritis in high- and low-poultry-density counties in Michigan between the years 1992 and 1999, an ecological study was conducted in the state of Michigan. A log-linear model was used to compare yearly, seasonal, age, and gender-specific incidence rates between county groupings. Counties with a high poultry density had a higher overall incidence of C. jejuni enteritis, particularly among children and young adults, compared with counties with low poultry density. The findings suggest that living in high-poultry-density counties is associated with higher odds for C. jejuni enteritis. This may be due to occupational exposure among poultry workers in these counties, but the findings in children suggest that indirect or environmental exposures may also play a role. Future studies should be conducted to investigate these issues.

Epidemiologic studies in a population-based childhood cancer registry in Northeast Hungary

BACKGROUND

Reports on the patterns of childhood cancer incidence are rare in Eastern Europe. To compare incidence rates and trends with international data, we processed records of the regional childhood cancer registry of Northeast Hungary.

PROCEDURE

Our computerized database contains population-based information on childhood cancer cases (<15 years) diagnosed in residents of two counties of Hungary: leukaemias from 1973, non-CNS solid tumours from 1978, and CNS tumours from 1984. After a retrospective evaluation of completeness of ascertainment, descriptive epidemiologic analyses were performed for the years of operation of the registry. Age-standardized annual incidence rates and age-specific incidences were calculated. Trends were evaluated in linear regression analysis.

RESULTS

The distribution of major histologic groups was similar to those observed in the Western countries with the exception that central nervous system tumours account for a higher percentage (27.3%). Average age-standardized annual incidence rates were as follows: all types of cancer: 120.7 per million; leukaemia: 37.3; CNS tumours: 31.6; lymphomas: 12.2; sympathetic nervous system tumours: 12.5; kidney tumours: 8.8. Significant increases were observed in incidence of leukaemia (average annual percent change AAPC: 0.7%), acute lymphoblastic leukaemia (AAPC: 1.9%), and all cancer groups (AAPC: 2.6%), but not in acute non-lymphocytic leukaemia or in CNS tumours. The strongest increases in cancer incidence were detected in the age group of 10-14 years (AAPC: 4.4%) and in infants (AAPC: 12.9%).

CONCLUSIONS

Incidences and trends are in accordance with the data in the latest literature, however, the contribution of CNS tumours and the rate of increase in total cancer incidence proved to be higher. Further detailed genetic and environmental studies of cancer registries may shed light on the etiology of the observed differences whether they represent a pattern specific for this region.

Hospitalization rates as outcome indicators of national medicinal drug policies: the example of gastrointestinal ulcer

National medicinal drug policies are employed around the world as a means of maximizing the benefits of medication use. An essential component to the implementation of these policies is their concurrent evaluation, which informs future policy implementation and strategic directions. The overall effect of the policy can be measured by monitoring changes in health outcomes and hospitalization rates for conditions that can be managed with appropriate medication use have been proposed as a potential outcome indicator of national medicinal drug policies. In this paper, a method for establishing the validity of this indicator is described. The method enables suitable conditions to be identified and takes into account potential confounding factors. To demonstrate this a case study of hospitalization rates for gastrointestinal ulcer is presented. The analysis shows that hospitalization rates are suitable as outcome indicators of quality medication use where the hospitalization rate is not confounded by changes in the population profile, disease prevalence and severity, diagnosis, hospital based policies, coding practices, environmental factors or hospital based treatments, but is responsive to changes in the utilization of medication. This method could be used in many countries for determining relevant and valid indicators for monitoring health outcomes.

Measuring community/environmental interventions: the Child Pedestrian Injury Prevention Project

OBJECTIVES

To assess the effectiveness of community/environmental interventions undertaken as part of the Child Pedestrian Injury Prevention Project (CPIPP).

SETTING

Three communities (local government areas) in the Perth metropolitan area, Western Australia.

METHODS

A quasiexperimental community intervention trial was undertaken over three years (1995-97). Three communities were assigned to either: a community/environmental road safety intervention and a school based road/pedestrian safety education program (intervention group 1); a school based road/pedestrian safety education program only (intervention group 2); or to no road safety intervention (comparison group). Quantification of the various road safety community/environmental activities undertaken in each community during the trial was measured, and a cumulative community activity index developed. Estimates of the volume and speed of vehicular traffic were monitored over a two year period.

RESULTS

Greater road safety activity was observed in intervention group 1 compared with the other groups. A significant reduction in the volume of traffic on local access roads was also observed over the period of the trial in intervention group 1, but not in the remaining groups.

CONCLUSIONS

The findings indicate that the various community/environmental interventions initiated in collaboration with CPIPP in intervention group 1 contributed, in part, to the observed reduction in the volume of traffic. A combination of community/environmental interventions and education are likely to reduce the rate of childhood pedestrian injury.

The incidence of dementia: a meta-analysis

OBJECTIVE

To carry out a meta-analysis of the age-specific incidence of all dementias, including AD and vascular dementia.

BACKGROUND

Several meta-analyses have been carried out on dementia prevalence, but none on its incidence.

METHODS

We used loess-curve fitting to analyze data from 23 published studies reporting age-specific incidence data.

RESULTS

The incidence of both dementia and AD rose exponentially up to the age of 90 years, with no sign of leveling off. The incidence rates for vascular dementia varied greatly from study to study, but the trend was also for an exponential rise with age. There was no sex difference in dementia incidence (p = 0.21), but women tended to have a higher incidence of AD in very old age, and men tended to have a higher incidence of vascular dementia at younger ages. East Asian countries had a lower incidence of dementia than Europe (p = 0.0004), and also tended to have a lower incidence of AD.

CONCLUSIONS

The incidence of dementia rises exponentially to the age of 90 years. Any sex differences are small, and incidence is lower in East Asia than in Europe.

Hepatoblastoma incidence in the United States from 1973 to 1992

BACKGROUND

There is recent evidence to suggest that extremely low birth weight is associated with the occurrence of hepatoblastoma.

PROCEDURE

In light of this possibility, we evaluated trends in hepatoblastoma incidence in the United States among children age 4 years and younger.

RESULTS

We found an increasing trend (5.2%) in hepatoblastoma incidence over the past two decades, a period that corresponds with improved survival of very low birth weight children.

CONCLUSION

Future studies of hepatoblastoma that incorporate birth weight are appropriate.

The PRECEDE-PROCEED model: application to planning a child pedestrian injury prevention program

OBJECTIVES

The objectives were first, to modify the PRECEDE-PROCEED model and to use it is as a basis for planning a three year intervention trial that aims to reduce injury to child pedestrians. A second objective was to assess the suitability of this process for planning such a relatively complex program.

SETTING

The project was carried out in 47 primary schools in three local government areas, in the Perth metropolitan area.

METHODS

The program was developed, based on extensive needs assessment incorporating formative evaluations. Epidemiological, psychosocial, environmental, educational, and demographic information was gathered, organised, and prioritised. The PRECEDE-PROCEED model was used to identify the relevant behavioural and environmental risk factors associated with child pedestrian injuries in the target areas. Modifiable causes of those behavioural and environmental factors were delineated. A description of how the model facilitated the development of program objectives and subobjectives which were linked to strategy objectives, and strategies is provided.

RESULTS

The process used to plan the child pedestrian injury prevention program ensured that a critical assessment was undertaken of all the relevant epidemiological, behavioural, and environmental information. The gathering, organising, and prioritising of the information was facilitated by the process.

CONCLUSIONS

The use of a model such as PRECEDE-PROCEED can enhance the development of a child injury prevention program. In particular, the process can facilitate the identification of appropriate objectives which in turn facilitates the development of suitable interventions and evaluation methods.

Infant cancer in the U.S.: histology-specific incidence and trends, 1973 to 1992

BACKGROUND

Many cancers in infants demonstrate unique epidemiologic, clinical, and genetic characteristics compared with cancers in older children. Few epidemiologic reports, however, have focused on this important age group.

METHODS

Population-based data from the Surveillance, Epidemiology, and End Results (SEER) program were used to estimate relative frequency, incidence rates, and average annual percentage change of rates among children in their first year of life (infants) who were diagnosed with a malignant neoplasm from 1973 to 1992 (N = 1461).

RESULTS

The greatest proportion of cases (12%) was diagnosed during the first month of life, with extracranial neuroblastoma accounting for 35% of this total. Overall, the average annual incidence rate was 223/1,000,000 infants. Extracranial neuroblastoma was the most common infant malignancy (58/1,000,000 infants per year), followed by leukemias (37/1,000,000), brain and central nervous system (CNS) tumors (34/1,000,000), and retinoblastoma (27/1,000,000). White infants had a 32% higher incidence rate than black infants. The average annual percentage increase in rates for all cancer from 1973 to 1992 was 2.9% (95% CI: 1.9%, 3.8%). For neoplasms with at least 100 cases, increasing trends were greatest for retinoblastoma (4.6%), CNS (4.1%), and extracranial neuroblastoma (3.4%).

CONCLUSIONS

Incidence rates increased notably over the study period. Future studies should consider the unique presentation of infants with cancer when developing new hypotheses related to cancer etiology and gene-environment interactions.

Trends in the stage specific incidence of prostate carcinoma in the Detroit metropolitan area, 1973-1994

BACKGROUND

Much of the recent increase in prostate carcinoma incidence has been attributed to screening with prostate specific antigen (PSA). Controversy exists as to whether this screening will ultimately impact prostate carcinoma mortality. Until adequate time elapses since PSA screening became widespread, or a randomized trial of PSA screening is completed, the effect of PSA screening on prostate carcinoma mortality cannot be determined. In the interim, stage specific prostate carcinoma incidence rates may provide an indication of the effect of PSA screening.

METHODS

Annual stage specific age-adjusted prostate carcinoma incidence rates for the years 1973 through 1994 were obtained from the Metropolitan Detroit Cancer Surveillance System (MDCSS), a member of the National Cancer Institute's Surveillance, Epidemiology and End Results (SEER) Program. These incidence rates were analyzed for trends using Poisson regression analysis.

RESULTS

There were 10,801 cases of prostate carcinoma in black men and 31,501 in white men during the 22-year period. Incidence rates for stages of local and regional prostate carcinoma reached a maximum in 1992 and 1993. Distant stage prostate carcinoma incidence has steadily declined since 1989 (P < 0.001), the year in which the increasing trend in the incidence rates for local and regional stage prostate carcinoma were first noted.

CONCLUSIONS

These findings suggest that a substantial proportion of early stage prostate carcinoma detected by PSA is in fact clinically important and that early detection of these carcinomas has resulted in a continuous decline in the stage of metastatic prostate carcinoma since 1989.

Trends in cancer incidence among children in the U.S

BACKGROUND

This report provides results of an analysis of temporal trends in childhood cancer incidence in the U.S. stratfied by age, sex, and to a lessor extent, race, within common histologic subtypes.

METHODS

Population-based data from nine registries of the Surveillance, Epidemiology, and End Results Program of the National Cancer Institute were analyzed. The analysis was limited to children age < or = 14 years. Cancer cases were restricted to those patients with a malignant neoplasm diagnosed between 1974 and 1991; more than 12,000 children were included. Average annual percentage change in incidence rates and corresponding 95% confidence intervals were estimated from the maximum likelihood method of Poisson regression.

RESULTS

Among children age < or = 14 years there was a 1% average yearly increase (95% CI 0.6, 1.3) in the incidence rates of all malignant neoplasms combined. The average annual percentage change was similar for males and females, and slightly higher for black children compared with white children. Rates increased an average of 2% or more per year for astroglial tumors, rhabdomyosarcomas, germ cell tumors, and osteosarcomas. The average annual percentage change for acute lymphoid leukemia was 1.6% and trends were somewhat stronger for blacks than whites. Cancer trends, in general, were strongest in young children. In particular, increases in astroglial tumors and rhabdomyosarcomas were most apparent among children age < 3 years, and for retinoblastoma and neuroblastoma among children in their first year of life. The average annual percentage change for acute lymphoid leukemia did not vary dramatically with age, however children age < 2 years had stronger trends compared with older children. We found little evidence for increasing trends in Wilms' tumor, primitive neuroectodermal tumors, or hematopoietic neoplasms other than acute lymphoid leukemia.

CONCLUSIONS

These results suggest that cancer occurrence among children within specific histologies increased modestly in the U.S. between 1974 and 1991, and that the increases were most apparent among young children.