Time Trend Effects Research Articles

Seasonality of Testicular Torsion: A 10-Year Nationwide Population Based Study

Using a 10-year nationwide data set, we examined seasonal variability in the monthly incidence of testicular torsion in Taiwan. We also investigated the association between meteorological factors (ambient temperature, relative humidity, atmospheric pressure, rainfall and total hours of sunshine) and testicular torsion, stratified by age group. This study retrieved data from the National Health Insurance Research Database. We identified 1,782 hospitalizations for testicular torsion between 2000 and 2009. Spearman's rank correlation was used to explore possible associations between climatic parameters and the monthly incidence of testicular torsion. In addition, we used the ARIMA method (Auto-Regressive Integrated Moving Average) to test for seasonality in the incidence of testicular torsion. The results demonstrated a fairly similar seasonal pattern in monthly incidence rates for testicular torsion across both age groups and the combined groups. January (midwinter) had the highest rates, which decreased in April to a trough in June (early summer). After adjusting for the time trend effect and climatic parameters, the ARIMA regression revealed that January had a significantly higher monthly incidence of testicular torsion compared to February. In addition, our results indicated that the monthly incidence of testicular torsion was negatively associated with ambient temperature. Our results suggest that the monthly incidence of testicular torsion was significantly associated with seasonality and ambient temperature.

Asian Dust Storm Events are Associated With an Acute Increase in Pneumonia Hospitalization

This study aims to examine the association of Asian dust storm (ADS) events with the daily number of pneumonia admissions using 10-year population-based data in the Taipei metropolitan region. We identified 1,933,247 admissions with a principal discharge diagnosis of pneumonia between 2000 and 2009. The auto-regressive integrated moving average (ARIMA) method was used to examine the associations between ADS episodes and the logarithm of the daily number of pneumonia hospitalizations. There was a significant difference in the mean number of daily pneumonia admissions between ADS event days, post-ADS event days, and non-ADS event days (P < .001); the mean number of daily admissions for ADS event days, post-ADS event days, and non-ADS event days were 292.5, 305.7, and 279.0, respectively. After adjusting for the time-trend effect, ambient temperature, and SO(2), CO, and O(3), the ARIMA showed that compared with non-ADS event days, ADS event days and post-ADS event days 1 through 4 had a significantly higher mean number of pneumonia admissions for the total group. Our results suggest that ADS event days and post-ADS days 1 through 4 had significantly higher mean numbers of pneumonia admissions than non-ADS days.

Seasonal Variation of Chemical Species Associated With Short-Term Mortality Effects of PM2.5 in Xi’an, a Central City in China

The authors conducted a time-series analysis to examine seasonal variation of mortality risk in association with particulate matter less than 2.5 μm in aerodynamic diameter (PM(2.5)) and chemical species in Xi'an, China, using daily air pollution and all-cause and cause-specific mortality data (2004-2008). Poisson regression incorporating natural splines was used to estimate mortality risks of PM(2.5) and its chemical components, adjusting for day of the week, time trend, and meteorologic effects. Increases of 2.29% (95% confidence interval: 0.83, 3.76) for all-cause mortality and 3.08% (95% confidence interval: 0.94, 5.26) for cardiovascular mortality were associated with an interquartile range increase of 103.0 μg/m(3) in lagged 1-2 day PM(2.5) exposure. Stronger effects were observed for the elderly (≥65 years), males, and cardiovascular diseases groups. Secondary components (sulfate and ammonium), combustion species (elemental carbon, sulfur, chlorine), and transition metals (chromium, lead, nickel, and zinc) appeared most responsible for increased risk, particularly in the cold months. The authors concluded that differential association patterns observed across species and seasons indicated that PM(2.5)-related effects might not be sufficiently explained by PM(2.5) mass alone. Future research is needed to examine spatial and temporal varying factors that might play important roles in modifying the PM(2.5)-mortality association.

Short-term effects of black smoke on cardiovascular hospitalization in elderly in Nis, Serbia

In past few years numerous epidemiological studies bring new evidence on the effects of particle air pollution on cardiovascular hospitalizations. The aim of our paper was to investigate the association between ambient concentrations of black smoke (BS) and daily total non-accidental cardiovascular hospitalizations in elderly in Nis. The daily mean number of all age cardiovascular hospitalizations was 12.46?6.26 (0 to 38) and 5.92?3.29 (0 to 20) among person ? 65 yrs. Daily measurements for black smoke (BS) and SO2, as well as the daily number of cardiovascular hospitalization among person ? 65 yrs of age, have been collected. BS (?g/m3) was measured by the refractometry method and SO2 (?g/m3) by spectrophotometer. Generalized linear model extending Poisson regression was applied. The effects of time trend, seasonal variations, day of week, temperature, relative humidity and barometric pressure were adjusted. Estimated OR of unipolutant regression model for among person ? 65 yrs was 1.00135 (95% CI: 0,97835 to 1,02489), and estimated OR of bipolutant model was 1,00975 (95% CI: 0,99457 to 1,02394) per 10?g/m3. The results do not support findings from previous studies that had shown an increase in the number of cardiovascular hospitalization in elderly in association with black smoke.

Remifentanil Prevents Tourniquet-Induced Arterial Pressure Increase in Elderly Orthopedic Patients under Sevoflurane/N2O General Anesthesia

Aims: Prolonged tourniquet inflation produces a hyperdynamic cardiovascular response. We investigated the effect of continuous remifentanil infusion on systemic arterial pressure, heart rate, and cardiac output changes during prolonged tourniquet use in elderly patients under sevoflurane/N2O general anesthesia.Methods: Thirty female patients scheduled for knee replacement arthroplasty were infused with either remifentanil at a target organ concentration of 2.0 ng/mL (remifentanil group, n = 15) or saline (control group, n = 15) after induction of anesthesia. Anesthesia was maintained with sevoflurane and N2O. Heart rate (HR), systolic arterial pressure (SAP), diastolic arterial pressure (DAP), cardiac index (CI), total systemic vascular resistance index (TSVRI), BIS, end-tidal sevoflurane concentration (EtSEVO), and end-tidal carbon dioxide concentration (EtCO2) were measured during the study period.Results: There were significant differences in mean HR, SAP, DAP, and EtSEVO over time between the groups (P = 0.047, P < 0.001, P = 0.017, and P < 0.001, respectively). There was a statistically significant time trend effect (P < 0.001) in HR, SAP, DAP, and CI between the groups, with a statistically significant time-group interaction between the two groups (P = 0.02, 0.007, 0.001, 0.01, respectively).Conclusion: The present study demonstrated that infusion with remifentanil prevented an increase in hemodynamic pressure during tourniquet inflation in elderly patients under sevoflurane/N2O general anesthesia.

Abstract P304: Effect of Benchmarking Projects on Outcome of Cabg Surgery: Challenges and Prospects Regarding Quality Improvement Initiative

Background: To improve quality of cardiovascular surgery, Japan Cardiovascular Surgery Database (JCVSD) was established since 2000 and started benchmarking profect. Though importance of quality improvement initiative has been emphasized in many researches, little study has reported those effects on outcomes. Methods and results: To examine the time-trend effects in initial JCVSD participants (n=44), we identified 8224 isolated CABG procedures performed between 2004 and 2007. The impact of surgery year was examined using a multiple logistic regression model setting previously identified clinical risk factors and surgery year as fixed effects. To examine the difference of outcomes between initial participants (n=44) and halfway participants (n=55), we identified 3882 isolated CABG procedures performed in 2007. The difference between two hospital groups were examined using a multiple logistic regression model setting clinical risk factors and hospital procedure volume, hospital groups as fixed effects. As for operative mortality, odds ratio of surgery year was 0.88 (p = 0.083). OE ratios of operative mortality were 0.71 in 2004, 0.73 in 2005, 0.63 in 2006, and 0.54 in 2007. As for composite mortality and major morbidities (reoperation, stroke, dialysis, infection, and prolonged ventilation), odds ratio of surgery year was 0.97 (p = 0.361). OE ratios of composite mortality and morbidities were 1.01 in 2004, 1.04 in 2005, 1.04 in 2006, and 0.94 in 2007. Compared with halfway participants, initial participant had significantly lower rate of operative mortality (OR=0.527, p=0.008) and composite mortality and major morbidities (OR 0.820, p = 0.047). Conclusions: This study demonstrated that quality improvement initiative for cardiovascular surgery has positive impact on risk-adjusted outcomes. While the primary target of benchmarking was 30-day mortality in Japan, major morbidities were less affected by those activities. Preoperative risk and risk adjusted mortality in initial participants surgery year 2004 2005 2006 2007 number of procedure 1831 2211 2125 2057 raw operative mortality rate 2.30% 2.50% 2.30% 1.80% expected operative mortality rate 3.25% 3.43% 3.65% 3.35% observed/expected mortality ratio 0.71 0.73 0.63 0.54

Changes in the socio-demographic patterning of late adolescent health risk behaviours during the 1990s: analysis of two West of Scotland cohort studies

BackgroundSubstance use and sexual risk behaviour affect young people's current and future health and wellbeing in many high-income countries. Our understanding of time-trends in adolescent health-risk behaviour is largely based on routinely collected survey data in school-aged adolescents (aged 15 years or less). Less is known about changes in these behaviours among older adolescents.MethodsWe compared two cohorts from the same geographical area (West of Scotland), surveyed in 1990 and 2003, to: describe time-trends in measures of smoking, drinking, illicit drug use, early sexual initiation, number of opposite sex sexual partners and experience of pregnancy at age 18-19 years, both overall and stratified by gender and socioeconomic status (SES); and examine the effect of time-trends on the patterning of behaviours by gender and SES. Our analyses adjust for slight between-cohort age differences since age was positively associated with illicit drug use and pregnancy.ResultsRates of drinking, illicit drug use, early sexual initiation and experience of greater numbers of sexual partners all increased significantly between 1990 and 2003, especially among females, leading to attenuation and, for early sexual initiation, elimination, of gender differences. Most rates increased to a similar extent regardless of SES. However, rates of current smoking decreased only among those from higher SES groups. In addition, increases in 'cannabis-only' were greater among higher SES groups while use of illicit drugs other than cannabis increased more in lower SES groups.ConclusionMarked increases in female substance use and sexual risk behaviours have implications for the long-term health and wellbeing of young women. More effective preventive measures are needed to reduce risk behaviour uptake throughout adolescence and into early adulthood. Public health strategies should reflect both the widespread prevalence of risk behaviour in young people as well as the particular vulnerability to certain risk behaviours among those from lower SES groups.

Air pollutants and morbidity of cardiopulmonary diseases in a semi-urban Greek peninsula

Abstract Aim To access the relationship between the frequency of hospitalizations due to respiratory and cardiovascular diseases and air pollution. Material-method Time series study during a seven year period (2001–2007) in a semi-urban tourist Greek peninsula. Data were collected from the computerized database of Volos General Hospital and included on a daily basis all emergency admissions of adults (>14 years old) which required hospitalization due to respiratory or cardiovascular problems. Daily concentrations of ambient pollutants [particulate matter with aerodynamic diameter less than 10 mm (PM10), carbon monoxide (CO), sulfur dioxide (SO2), nitrogen oxides (NO, NO2, NOX) and ozone (O3)] were obtained from three monitoring stations. The impact of air pollutants on morbidity was studied through time series analysis. The effects of time trend, season, and other cyclical factors, temperature, and humidity were accounted for. Autocorrelation and overdispersion were corrected. Results There were significant associations between hospitalizations and all indicators of air pollution. Daily elevations in the concentrations of PM10, NO, CO and O3 increased significantly the number of hospitalizations for respiratory/cardiovascular causes both on the same day and at the next day (p Conclusion Our findings suggest a significant relationship between morbidity burden of respiratory and cardiovascular diseases and the levels of air pollution; these results underline that reinforcement of measures which target to control ambient pollution, is necessary.

Disability in rheumatoid arthritis in the era of biological treatments

ObjectiveRheumatoid arthritis (RA) is a disabling disease. The authors studied the impact of new, expensive and occasionally toxic biological treatments on disability outcomes in real-world populations of patients with RA.MethodsThe...

HEALTH EFFECT OF FINE PARTICULATE MATTER ON DAILY EMERGENCY ROOM VISITS OF CARDIOVASCULAR DISEASE: A TIME-SERIES STUDY

Background and Aims:Beijing, as the host of Olympics 2008, is developing quickly in economic and social areas. The air pollution pattern has been changing from the traditional coal burning pollution to complex pollution with vehicle exhaust, biomass combustion, dust from nature and construction, energy power and others. To evaluate the association between air particulate matter and daily hospital emergency room visits (HERVs) of cardiovascular disease, we performed a time-series analysis on health effects of air pollution. in Beijing. Methods:A Poisson regression for the association of the daily air pollutants with daily HERVs for cardiovascular disease in Beijing from 2007.1.1-2008.12.31 was performed using generalized additive model. The effects of time trend, seasonal variations, temperature and humidity were adjusted by smooth functions. Daily mean concentration of SO2, NO2, PM10 and PM2.5 were introduced into the core model. Relative risks (RR) of cardiovascular disease (per10ug/m3 increase in air pollutant concentration) were calculated. Lagged effects of air pollutants and multi-pollutant model were concerned as well. Results:The results showed consistent correlation between air pollutants and daily HERVs. The increase of daily number of HERVs for cardiovascular disease for a 10ug/m3 increase in SO2, NO2, PM10, PM2.5 were: 0.36% (0.29%~1.01%), 1.02% (0.00%~1.74%), 0.32% (0.09%~0.55%), and 0.41%(0.19%~0.90%), respectively. The relative risks for daily HERVs in sub-categories and elderly were slightly higher. The multi-pollutants models showed the effects of SO2 were the most stable, while the PM2.5 had small increase when the gases were introduced into model. This study also found lagged effect of particulate matter on daily HERVs for cardiovascular disease. Conclusions:The current air pollution in Beijing has a harm effects on daily cardiovascular emergency room visits. The effects of particulate matter were more considering, while the elder population is the most sensitive.

Analyzing the effects of air pollution and mortality by generalized additive models with robust principal components

In this paper, we propose generalized additive models (GAMs) based on the robust principal component analysis (PCA) methods, to quantify the association between daily mortality and air pollutant concentrations, especially PM10, CO, NO2, SO2 and O3, for confounding effects of long-term time trend, seasonality, weekday, and meteorological factors. The two PCA methods that will be applied into the GAM are: one is classic PCA (CPCA) and the other is robust PCA (RPCA) with minimum covariance determinant, called CPCA–GAM and RPCA–GAM, respectively. Comparing the analyses between GAM, CPCA–GAM, and RPCA–GAM, we can reach to the conclusions as follows: (1) results from CPCA–GAM and RPCA–GAM are consistent with each other; (2) RPCA is much more effective tool to detect outliners than CPCA; and (3) because PCA eliminates the collinearity between covariates, the coefficients of air pollutants have shown to be more significant than GAM without PCA.

Intramural coronary arteries and outcome of neonatal arterial switch operation

To evaluate the impact of coronary patterns with intramural arteries on the outcome of arterial switch operation (ASO) in neonates with transposition of the great arteries (TGA). Between 1987 and 2008, 919 neonates underwent ASO for TGA. Forty-six (5.0%) had intramural coronary arteries. Intramural course involved the left main coronary artery in 28 of the 46 cases (61%), the left anterior descending artery in 12 patients (26%), the right coronary artery in three and both right and left coronary arteries in three cases. Various techniques were used to manage the coronary arteries: ASO without coronary relocation in one, ASO with coronary transfer as a single coronary button in nine and ASO with coronary transfer as two separate buttons in 36 patients (additional pericardial patches were implanted to orientate the coronary button in nine cases or enlarge the coronary ostium in three cases). The intramural course was unroofed in most cases (after 1995). There were 13 deaths (28%): two intra-operative, nine before discharge from the hospital and two after discharge; during the same period, overall mortality in the 873 neonates with other coronary patterns was 3.9%. Actuarial survival at 10 years was 71 + or - 7%. Most deaths (11/13, i.e., 85%) were related to coronary complications. No time-trend effect was noted regarding mortality. Non-fatal coronary lesions were detected in eight patients (three with clinical evidence of myocardial infarction and five without). Five patients underwent re-operation for coronary revascularisation. Actuarial freedom from coronary events at 10 years was 46 + or - 10%. After a mean follow-up of 8.3 + or - 4.8 years, left ventricular function was normal in 97% of the survivors; minor ischaemic sequelae were present in two patients. Coronary patterns with intramural arteries remain associated with high coronary mortality and morbidity following neonatal ASO, even in the current era. The association of slit-like deformation of the ostium, stenosis of the intramural course and abnormal angle of take-off might explain the difficulty in coronary transfer. The technique of coronary transfer should be individually adapted to each anatomical situation. The place of patch ostioplasty of the intramural artery remains to be determined.

Application of 'stepped-wedge design' methodology in randomized controlled trials

In this article, two research cases are employed to show the rationale of the stepped-wedge design, under what situations that such a design is desirable, and how it can be implemented. Stepped-wedge design seems to suit to randomized controlled trials in which the entire study population will receive intervention programs as they would "provide more advantages than harm". When intervention can not be given to all the targets simultaneously due to limited resources, this design is particularly useful. The stepped-wedge design is also relevant when there is a hope to detect or control the time trend effect on the effectiveness of the intervention strategy. On the other hand, however, this design requires longer trial duration and presents a number of statistical challenges. Hence, careful planning and monitoring are essential to ensure that a robust evaluation is undertaken.

Seasonal Variation in the Incidence of Gastroesophageal Reflux Disease

BackgroundTo examine the seasonal variation in the incidence of gastroesophageal reflux disease (GERD) for different gender and age groups and its association with climatic parameters (ambient temperature, relative humidity, atmospheric pressure, rainfall, and hours of sunshine). MethodsA total of 76,636 ambulatory care visits for the treatment of GERD between 2001 and 2006 were included. Monthly GERD incidence rates per 10,000 people were calculated over 72months and categorized by gender and age groupings (19–44, 45–64, and ≥65years). Seasonality is a general component of time-series patterns. The auto-regressive integrated moving average (ARIMA) regression method was used to evaluate the effects of climatic and monthly factors on GERD incidence rates after adjusting for the time-trend effect. ResultsSeasonal trends showed an incidence peak in October to December, followed by a sharp decrease in January, and a trough in February; a fairly similar seasonal pattern of GERD incidence was apparent for gender, age, and combined groups. The ARIMA test for seasonality found a significant association for the total group (P<0.01), for female (P<0.05) patients, and for the 45 to 64years (P<0.01) and >64years (P<0.01) age groups. The ARIMA models also showed that relative humidity was negatively related to monthly GERD incidence rates for men (P<0.01) and the >64years (P<0.01) age group. ConclusionData showed seasonal variations in GERD incidence. Relative humidity was associated with monthly GERD incidence rates for men and the >64years age group.

Air Temperature and the Occurrence of Myocardial Infarction in Augsburg, Germany

Air temperature changes have been associated with cardiovascular mortality and morbidity. The objective of this study was to examine in detail the registry-based myocardial infarction (MI) rates and coronary deaths in relation to air temperature in the area of Augsburg, Germany. Between 1995 and 2004, the Monitoring Trends and Determinants on Cardiovascular Diseases/Cooperative Health Research in the Region of Augsburg (MONICA/KORA) registry recorded 9801 cases of MI and coronary deaths. Over the same period, meteorological parameters and air pollutant concentrations were measured in the study region. Poisson regression analyses adjusting for time trend, relative humidity, season, and calendar effects were used to estimate immediate, delayed, and cumulative temperature effects on the occurrence of MIs. The daily rates of total MI, nonfatal and fatal events, and incident and recurrent events were analyzed. For the total MI cases, a 10 degrees C decrease in 5-day average temperature was associated with a relative risk of 1.10 (95% confidence interval, 1.04 to 1.15). The effect of temperature on the occurrence of nonfatal events showed a delayed pattern, whereas the association with fatal MI was more immediate. No association could be observed for recurrent events. The effects of temperature decreases on total MI cases were more pronounced in years with higher average temperatures and were visible in summer. We observed an inverse relationship between temperature and MI occurrence not only during winter but also during summer. Thus, our results suggest not a pure "cold effect" but an influence of unusual temperature decreases.

Increasing Clinical Virulence in Two Decades of the Italian HIV Epidemic

The recent origin and great evolutionary potential of HIV imply that the virulence of the virus might still be changing, which could greatly affect the future of the pandemic. However, previous studies of time trends of HIV virulence have yielded conflicting results. Here we used an established methodology to assess time trends in the severity (virulence) of untreated HIV infections in a large Italian cohort. We characterized clinical virulence by the decline slope of the CD4 count (n = 1423 patients) and the viral setpoint (n = 785 patients) in untreated patients with sufficient data points. We used linear regression models to detect correlations between the date of diagnosis (ranging 1984–2006) and the virulence markers, controlling for gender, exposure category, age, and CD4 count at entry. The decline slope of the CD4 count and the viral setpoint displayed highly significant correlation with the date of diagnosis pointing in the direction of increasing virulence. A detailed analysis of riskgroups revealed that the epidemics of intravenous drug users started with an apparently less virulent virus, but experienced the strongest trend towards steeper CD4 decline among the major exposure categories. While our study did not allow us to exclude the effect of potential time trends in host factors, our findings are consistent with the hypothesis of increasing HIV virulence. Importantly, the use of an established methodology allowed for a comparison with earlier results, which confirmed that genuine differences exist in the time trends of HIV virulence between different epidemics. We thus conclude that there is not a single global trend of HIV virulence, and results obtained in one epidemic cannot be extrapolated to others. Comparison of discordant patterns between riskgroups and epidemics hints at a converging trend, which might indicate that an optimal level of virulence might exist for the virus.

Eating late in the evening is associated with childhood obesity in some age groups but not in all children: the relationship between time of consumption and body weight status in U.S. children

BackgroundSome studies in adults indicate a positive correlation between eating later in the day and overall energy intake as well as body weight status. Thus, the time of food intake may be a risk factor in childhood obesity. This study was designed to describe the proportion of energy consumed in the time from 4 pm to midnight measured in two-hour increments and to determine a potential association between the time of proportion of energy consumed and body weight status.MethodsDietary, anthropometric, and socio-demographic data of 2–18 year olds (N = 11,072) of the National Health and Nutrition Examination Survey (NHANES) 1999–2004 was examined to describe the proportion of total energy consumed within two-hour time periods between 4 pm and midnight. To examine the potential association between eating later in the day and body weight status, generalized estimating equations (GEE) models were used to quantify the effect of time trends (proportion of total energy consumed in each 2-hour time period from 4 pm to 11.59 pm) on body weight status. Analysis was conducted in the total sample and in subgroups stratified by sex, ethnic group (Non-Hispanic white, Non-Hispanic black, Mexican American, Other Hispanic, and Other Race including multi-racial) and age group (2–5, 6–11, and 12–18 year olds). Complex sample survey analysis were used to assess differences at a significance level of p-value < 0.05.ResultsProportion of energy consumed varied by sex, ethnic group, and age groups between 4 pm and 11.59 pm. Compared to healthy weight children, overweight school-age children consumed significantly higher while overweight adolescents consumed significantly lower proportions of total daily energy with each advancing two-hour time increment.ConclusionThe association between the circadian rhythm of eating and body weight status needs to be investigated further to examine the effect of time of consumption on the risk of childhood obesity. Especially longitudinal studies in diverse child populations would help elucidate the importance of time of eating on obesity.

Pollen Loads and Allergic Rhinitis in Darwin, Australia: A Potential Health Outcome of the Grass-Fire Cycle

Although the prevalence of asthma and allergic rhinitis has been increasing in tropical regions, little is known about the allergenicity of pollens from tropical plant families or the importance of ongoing environmental changes. We investigated associations between daily average pollen counts of several tropical plant families and sales of medications for the treatment of allergic rhinitis in Darwin, Australia-a tropical setting in which grass abundance has increased due to increased fire frequencies and the introduction of African pasture grasses. Daily pollen counts with detailed identification of plant species were undertaken in conjunction with a weekly survey of flowering plant species from April 2004 to November 2005. Five pharmacies provided daily sales data of selected medications commonly used to treat allergic rhinitis. We used generalized linear modeling to examine outcomes. All analyses accounted for the potential confounding effects of time trends, holidays, respiratory viral illnesses, meteorological conditions, and air pollution. The peak total pollen count was 94 grains/m(3). Despite the low levels of Poaceae (grass) pollen (maximum daily count, 24 grains/m(3)), there was a clear association with daily sales of anti-allergic medications greatest at a lag of 1 day. Sales increased by 5% with an interquartile range rise (3 grain/m(3)) in Poaceae pollen (5.07%, 95%CI 1.04%, 9.25%). No associations were observed with pollen from other plant families. Although further testing is required, we suggest that an overlooked aspect of the "grass-fire cycle" that is degrading many tropical landscapes, could be an increase in the prevalence of allergic rhinitis.

Modeling fault among motorcyclists involved in crashes

Singapore crash statistics from 2001 to 2006 show that the motorcyclist fatality and injury rates per registered vehicle are higher than those of other motor vehicles by 13 and 7 times, respectively. The crash involvement rate of motorcyclists as victims of other road users is also about 43%. The objective of this study is to identify the factors that contribute to the fault of motorcyclists involved in crashes. This is done by using the binary logit model to differentiate between at-fault and not-at-fault cases and the analysis is further categorized by the location of the crashes, i.e., at intersections, on expressways and at non-intersections. A number of explanatory variables representing roadway characteristics, environmental factors, motorcycle descriptions, and rider demographics have been evaluated. Time trend effect shows that not-at-fault crash involvement of motorcyclists has increased with time. The likelihood of night time crashes has also increased for not-at-fault crashes at intersections and expressways. The presence of surveillance cameras is effective in reducing not-at-fault crashes at intersections. Wet-road surfaces increase at-fault crash involvement at non-intersections. At intersections, not-at-fault crash involvement is more likely on single-lane roads or on median lane of multi-lane roads, while on expressways at-fault crash involvement is more likely on the median lane. Roads with higher speed limit have higher at-fault crash involvement and this is also true on expressways. Motorcycles with pillion passengers or with higher engine capacity have higher likelihood of being at-fault in crashes on expressways. Motorcyclists are more likely to be at-fault in collisions involving pedestrians and this effect is higher at night. In multi-vehicle crashes, motorcyclists are more likely to be victims than at-fault. Young and older riders are more likely to be at-fault in crashes than middle-aged group of riders. The findings of this study will help to develop more targeted countermeasures to improve motorcycle safety and more cost-effective safety awareness program in motorcyclist training.

Modelling of malaria temporal variations in Iran

To model the temporal variations in malaria episodes in a hypo-endemic area of Iran and to assess the feasibility of an epidemic early warning system. Malaria episode data for Kahnooj District, south-east Iran, were collected from the local health system for the period 1994-2002. Plasmodium species-specific models were generated using Poisson regression. Starting with a simple model which included only temporal effects, we iteratively added more explanatory variables to maximize goodness of fit. Of 18,268 recorded malaria episodes, more than 67% were due to P. vivax. In addition to seasonality and secular trend, we found that incorporating a 1-month time lag between key meteorological variables and the predicted number of cases maximized goodness of fit. Maximum temperature, mean relative humidity and previous numbers of malaria cases were the most important predictors. These were included in the model with lags of no less than three dekads, i.e. three 10-day periods or effectively 1 month. Simple models based on climatic factors and information on past case numbers may be useful in improving the quality of the malaria control programme in Iran, particularly in terms of assuring accurate targeting of interventions in time and space. The models developed in this study are based on explanatory data that incorporate a lag of 1 month (i.e. data that were recorded 21-50 days previously). In practice, this translates into an operational 'window' of 1 month. Provided appropriate modes of data exchange exist between key stakeholders and appropriate systems for operational response are in place, this type of early warning information has the potential to lead to significant reductions in malaria morbidity in Iran.