Novel Hendra Virus Variant Circulating in Black Flying Foxes and Grey-Headed Flying Foxes, Australia.

A novel Hendra virus variant, genotype 2, was recently discovered in a horse that died after acute illness and in Pteropus flying fox tissues in Australia. We detected the variant in flying fox urine, the pathway relevant for spillover, supporting an expanded geographic range of Hendra virus risk to horses and humans.

The Role of Eif6 in Skeletal Muscle Homeostasis Revealed by Endurance Training Co-expression Networks.

Regular endurance training improves muscle oxidative capacity and reduces the risk of age-related disorders. Understanding the molecular networks underlying this phenomenon is crucial. Here, by exploiting the power of computational modeling, we show that endurance training induces profound changes in gene regulatory networks linking signaling and selective control of translation to energy metabolism and tissue remodeling. We discovered that knockdown of the mTOR-independent factor Eif6, which we predicted to be a key regulator of this process, affects mitochondrial respiration efficiency, ROS production, and exercise performance. Our work demonstrates the validity of a data-driven approach to understanding muscle homeostasis.

Investigation of the Association Between Alcohol Outlet Density and Alcohol-Related Hospital Admission Rates in England: Study Protocol.

BACKGROUND: Availability of alcohol is a major policy issue for governments, and one of the availability factors is the density of alcohol outlets within geographic areas. OBJECTIVE: The aim of this study is to investigate the association between alcohol outlet density and hospital admissions for alcohol-related conditions in a national (English) small area level ecological study. METHODS: This project will employ ecological correlation and cross-sectional time series study designs to examine spatial and temporal relationships between alcohol outlet density and hospital admissions. Census units to be used in the analysis will include all Lower and Middle Super-Output Areas (LSOAs and MSOAs) in England (53 million total population; 32,482 LSOAs and 6781 MSOAs). LSOAs (approximately 1500 people per LSOA) will support investigation at a fine spatial resolution. Spatio-temporal associations will be investigated using MSOAs (approximately 7500 people per MSOA). The project will use comprehensive coverage data on alcohol outlets in England (from 2003, 2007, 2010, and 2013) from a commercial source, which has estimated that the database includes 98% of all alcohol outlets in England. Alcohol outlets may be classified into two broad groups: on-trade outlets, comprising outlets from which alcohol can be purchased and consumed on the premises (eg, pubs); and off-trade outlets, in which alcohol can be purchased but not consumed on the premises (eg, off-licenses). In the 2010 dataset, there are 132,989 on-trade and 51,975 off-trade outlets. The longitudinal data series will allow us to examine associations between changes in outlet density and changes in hospital admission rates. The project will use anonymized data on alcohol-related hospital admissions in England from 2003 to 2013 and investigate associations with acute (eg, admissions for injuries) and chronic (eg, admissions for alcoholic liver disease) harms. The investigation will include the examination of conditions that are wholly and partially attributable to alcohol, using internationally standardized alcohol-attributable fractions. RESULTS: The project is currently in progress. Results are expected in 2017. CONCLUSIONS: The results of this study will provide a national evidence base to inform policy decisions regarding the licensing of alcohol sales outlets.

The effect of intramedullary pin size and plate working length on plate strain in locking compression plate-rod constructs under axial load.

OBJECTIVE: To investigate the effect of intramedullary pin size and plate working length on plate strain in locking compression plate-rod constructs. METHODS: A synthetic bone model with a 40 mm fracture gap was used. Locking compression plates with monocortical locking screws were tested with no pin (LCP-Mono) and intramedullary pins of 20% (LCPR-20), 30% (LCPR-30) and 40% (LCPR-40) of intramedullary diameter. Two screws per fragment modelled a long (8-hole) and short (4-hole) plate working length. Strain responses to axial compression were recorded at six regions of the plate via three-dimensional digital image correlation. RESULTS: The addition of a pin of any size provided a significant decrease in plate strain. For the long working length, LCPR-30 and LCPR-40 had significantly lower strain than the LCPR-20, and plate strain was significantly higher adjacent to the screw closest to the fracture site. For the short working length, there was no significant difference in strain across any LCPR constructs or at any region of the plate. Plate strain was significantly lower for the short working length compared to the long working length for the LCP-Mono and LCPR-20 constructs, but not for the LCPR-30 and LCPR-40 constructs. CLINICAL SIGNIFICANCE: The increase in plate strain encountered with a long working length can be overcome by the use of a pin of 30-40% intramedullary diameter. Where placement of a large diameter pin is not possible, screws should be placed as close to the fracture gap as possible to minimize plate strain and distribute it more evenly over the plate.

Distal Normograde Intramedullary Pin and Locking Plate Placement in the Canine Humerus: A Cadaveric Study.

OBJECTIVE: To identify a repeatable anatomic landmark for pin insertion and to describe the technique for placement of a distal normograde intramedullary (IM) pin of approximately 35% of the IM diameter using this approach combined with a locking compression plate (LCP) on the medial aspect of the canine humerus. STUDY DESIGN: Ex vivo anatomic study. SAMPLE POPULATION: Canine cadavers (n=10 Greyhounds). METHODS: An anatomic landmark for pin insertion was identified based on three-dimensional reconstructions of previous elbow computed tomography studies and cadaveric dissection of the medial aspect of the humeral condyle. Bilateral distal normograde IM pin and LCP placement were performed and confirmed radiographically and by disarticulation and sagittal sectioning. RESULTS: The anatomic landmark for pin insertion was consistently identified in each specimen using the technique described. Distal normograde insertion of a 3.5 mm IM pin was possible in Greyhound cadaveric humeri at the described location in conjunction with a 3.5 mm LCP with fixed angle, locked screws. A monocortical locking screw was required to avoid interference with the IM pin in 28 of 60 of the 3 proximal screw holes. No pin interference was encountered in any of the distal screw holes. CONCLUSION: The anatomic landmark and technique described in our study enabled repeatable successful placement of a distal normograde IM pin of approximately 35% of the IM diameter combined with an LCP on the medial aspect of the canine humerus. This technique may be useful for locking plate-rod fixation of distal humeral diaphyseal fractures.

Acute effects of aircraft noise on cardiovascular admissions - an interrupted time-series analysis of a six-day closure of London Heathrow Airport caused by volcanic ash.

Acute noise exposure may acutely increase blood pressure but the hypothesis that acute exposure to aircraft noise may trigger cardiovascular events has not been investigated. This study took advantage of a six-day closure of a major airport in April 2010 caused by volcanic ash to examine if there was a decrease in emergency cardiovascular hospital admissions during or immediately after the closure period, using an interrupted daily time-series study design. The population living within the 55dB(A) noise contour was substantial at 0.7 million. The average daily admission count was 13.9 (SD 4.4). After adjustment for covariates, there was no evidence of a decreased risk of hospital admission from cardiovascular disease during the closure period (relative risk 0.97 (95% CI 0.75-1.26)). Using lags of 1-7 days gave similar results. Further studies are needed to investigate if transient aircraft noise exposure can trigger acute cardiovascular events.

Air Pollution and Subtypes, Severity and Vulnerability to Ischemic Stroke-A Population Based Case-Crossover Study.

BACKGROUND AND PURPOSE: Few studies have examined the association between air pollutants and ischemic stroke subtypes. We examined acute effects of outdoor air pollutants (PM10, NO2, O3, CO, SO2) on subtypes and severity of incident ischemic stroke and investigated if pre-existing risk factors increased susceptibility. METHODS: We used a time stratified case-crossover study and stroke cases from the South London Stroke Register set up to capture all incident cases of first ever stroke occurring amongst residents in a geographically defined area. The Oxford clinical and TOAST etiological classifications were used to classify subtypes. A pragmatic clinical classification system was used to assess severity. Air pollution concentrations from the nearest background air pollution monitoring stations to patients' residential postcode centroids were used. Lags from 0 to 6 days were investigated. RESULTS: There were 2590 incident cases of ischemic stroke (1995-2006). While there were associations at various lag times with several pollutants, overall, there was no consistent pattern between exposure and risk of ischemic stroke subtypes or severity. The possible exception was the association between NO2 exposure and small vessel disease stroke-adjusted odds ratio of 1.51 (1.12-2.02) associated with an inter-quartile range increase in the lag 0-6 day average for NO2. There were no clear associations in relation to pre-existing risk factors. CONCLUSIONS: Overall, we found little consistent evidence of association between air pollutants and ischemic stroke subtypes and severity. There was however a suggestion that increasing NO2 exposure might be associated with higher risk of stroke caused by cerebrovascular small vessel disease.

Assessing the impact of selective migration and care homes on geographical inequalities in health--a total population cohort study in Sheffield.

Selective migration and moves to care homes may potentially contribute to observed socioeconomic gradients in mortality across cities and regions. Sheffield has striking socioeconomic gradients in area-level mortality across the city. We examined for evidence of selective migration and assessed the contribution of migration to observed mortality gradients. We used a total population cohort (539737 in 2001), linked mortality data (2001-2010) and linked data from a health survey carried out in 2000 (66% response rate yielding 10185 responses). We used lower super-output areas and electoral wards as the spatial units of analysis. We found clear evidence of selective migration. In the 25-44 age band, relative risks of mortality were 1.71 (95% CI 1.37-2.12) in migrants from low to high deprivation areas compared with people remaining in low deprivation areas, and 0.53 (0.42-0.65) in migrants from high to low deprivation areas compared with people remaining in high deprivation areas. Relative risks shrank towards unity with increasing age. Characteristics of migrants and non-migrants (illness prevalence, indicators of socioeconomic status, smoking prevalence) ascertained before migration were largely consistent with the relative risks for mortality and indicated that people carried their risks with them. There was also a clear care homes effect, with higher mortality in electoral wards with higher care home bed provision rates. Overall, however, adjustment for selective migration, which included moves to care homes, made little difference to gradients in inequality across the city. Our results suggest that selective migration, including moves to care homes, do not explain existing socioeconomic gradients in area level mortality across Sheffield.

Outdoor air pollution, subtypes and severity of ischemic stroke--a small-area level ecological study.

BACKGROUND: Evidence linking outdoor air pollution and incidence of ischemic stroke subtypes and severity is limited. We examined associations between outdoor PM10 and NO2 concentrations modeled at a fine spatial resolution and etiological and clinical ischemic stroke subtypes and severity of ischemic stroke. METHODS: We used a small-area level ecological study design and a stroke register set up to capture all incident cases of first ever stroke (1995-2007) occurring in a defined geographical area in South London (948 census output areas; population of 267839). Modeled PM10 and NO2 concentrations were available at a very fine spatial scale (20 meter by 20 meter grid point resolution) and were aggregated to output area level using postcode population weighted averages. Ischemic stroke was classified using the Oxford clinical classification, the Trial of Org 10172 in Acute Stroke Treatment (TOAST) etiological classification, National Institutes of Health Stroke Scale (NIHSS) score and a pragmatic clinical severity classification based on Glasgow coma score, ability to swallow, urinary continence and death <2 days of stroke onset. RESULTS: Mean (SD) concentrations were 25.1 (1.2) ug/m(3) (range 23.3-36.4) for PM10 and 41.4 (3.0) ug/m(3) (range 35.4-68.0) for NO2. There were 2492 incident cases of ischemic stroke. We found no evidence of association between these pollutants and the incidence of ischemic stroke subtypes classified using the Oxford and TOAST classifications. We found no significant association with stroke severity using NIHSS severity categories. However, we found that outdoor concentrations of both PM10 and NO2 appeared to be associated with increased incidence of mild but not severe ischemic stroke, classified using the pragmatic clinical severity classification. For mild ischemic stroke, the rate ratio in the highest PM10 category by tertile was 1.20 (1.05-1.38) relative to the lowest category. The rate ratio in the highest NO2 category was 1.22 (1.06-1.40) relative to the lowest category. CONCLUSIONS: We found no evidence of association between outdoor PM10 and NO2 concentrations and ischemic stroke subtypes but there was a suggestion that living in areas with elevated outdoor PM10 and NO2 concentrations might be associated with increased incidence of mild, but not severe, ischemic stroke.

Bayesian hierarchical modelling of noisy spatial rates on a modestly large and discontinuous irregular lattice.

We present Bayesian hierarchical spatial model development motivated from a recent analysis of noisy small area response rate data, named the Booster data. The Booster data are postcode-level aggregates from a recent mail-out recruitment for a physical exercise intervention in deprived urban neighbourhoods in Sheffield, UK. Bayesian hierarchical Bernoulli-binomial spatial mixture zero-inflated Binomial models were developed for modelling overdispersion and for separation of systematic and random variations in the noisy and mostly low crude response rates. We present methods that enabled us to explore the underlying spatial rate variation, clustering of low or high response rate areas and neighbourhood characteristics that were associated with variations and patterns of invitation mail-outs, zero-response and response rates. Three spatial prior formulations, the intrinsic conditional autoregressive or (iCAR), the Besag-York-Mollié (BYM) and the modified BYM models, were explored for their performance on modelling sparse data on a modestly large and discontinuous irregular lattice. An in-depth Bayesian analysis of the Booster data is presented, with the resulting posterior estimation and inference implemented via Markov chain Monte Carlo simulation in WinBUGS. With increasing availability of spatial data referenced at fine spatial scales such as the postcode, the sparse-data situation and the Bayesian models and methods discussed herein should have considerable relevance to small area disease and health mapping and to spatial regression.

A system-wide approach to explaining variation in potentially avoidable emergency admissions: national ecological study.

BACKGROUND: Some emergency admissions can be avoided if acute exacerbations of health problems are managed by the range of health services providing emergency and urgent care. AIM: To identify system-wide factors explaining variation in age sex adjusted admission rates for conditions rich in avoidable admissions. DESIGN: National ecological study. SETTING: 152 emergency and urgent care systems in England. METHODS: Hospital Episode Statistics data on emergency admissions were used to calculate an age sex adjusted admission rate for conditions rich in avoidable admissions for each emergency and urgent care system in England for 2008-2011. RESULTS: There were 3 273 395 relevant admissions in 2008-2011, accounting for 22% of all emergency admissions. The mean age sex adjusted admission rate was 2258 per year per 100 000 population, with a 3.4-fold variation between systems (1268 and 4359). Factors beyond the control of health services explained the majority of variation: unemployment rates explained 72%, with urban/rural status explaining further variation (R(2)=75%). Factors related to emergency departments, hospitals, emergency ambulance services and general practice explained further variation (R(2)=85%): the attendance rate at emergency departments, percentage of emergency department attendances converted to admissions, percentage of emergency admissions staying less than a day, percentage of emergency ambulance calls not transported to hospital and perceived access to general practice within 48 h. CONCLUSIONS: Interventions to reduce avoidable admissions should be targeted at deprived communities. Better use of emergency departments, ambulance services and primary care could further reduce avoidable emergency admissions.

Mapping gender variation in the spatial pattern of alcohol-related mortality: a Bayesian analysis using data from South Yorkshire, United Kingdom.

Gender variation in the spatial pattern of alcohol-related deaths in South Yorkshire, UK for the period 1999 and 2003 was explored using two Bayesian modelling approaches. Firstly, separate models were fitted to male and female deaths, each with a fixed effect deprivation covariate and a random effect with unstructured and spatially structured terms. In a modification to the initial models, covariates were assumed estimated with error rather than known with certainty. In the second modelling approach male and female deaths were modelled jointly with a shared component for random effects. A range of different unstructured and spatially structured specifications for the shared and gender-specific random effects were fitted. In the best fitting shared component model a spatially structured prior was assumed for the shared component, while gender-specific components were assumed unstructured. Deprivation coefficients and random effect standard deviations were very similar between the gender-specific and shared component models. In each case the effect of deprivation was observed to be greater in males than in females, and slightly larger in the measurement error models than in the fixed covariate models. Greater variation was observed in the spatially smoothed estimates of risk for males versus females in both gender-specific and shared component models. The shared component explained a greater proportion of the male risk than it did the female risk. The analysis approach reveals the residual (unexplained by deprivation) gender-specific and shared risk surfaces, information which may be useful for guiding public health action.

Outdoor air pollution and incidence of ischemic and hemorrhagic stroke: a small-area level ecological study.

BACKGROUND AND PURPOSE: Evidence linking outdoor air pollution and incidence of stroke is limited. We examined effects of outdoor air pollution on the incidence of ischemic and hemorrhagic stroke at the population level focusing on middle-aged and older people. METHODS: We used a small-area level ecological study design and a stroke register set up to capture all incident cases of first-ever stroke occurring in a defined geographical area in south London (948 census output areas) where road traffic contributes to spatial variation in air pollution. Population-weighted averages were calculated for output areas using outdoor nitrogen dioxide and PM(10) concentrations modeled at a 20-m resolution. RESULTS: There were 1832 ischemic and 348 hemorrhagic strokes in 1995 to 2004 occurring among a resident population of 267 839. Mean (SD) concentration was 25.1 (1.2) µg/m(3) (range, 23.3-36.4 µg/m(3)) for PM(10) and 41.4 (3.0) µg/m(3) (range, 35.4-68.0 µg/m(3)) for nitrogen dioxide. For ischemic stroke, adjusted rate ratios per 10-µg/m(3) increase, for all ages, 40 to 64 and 65 to 79 years, respectively, were 1.22 (0.77-1.93), 1.12 (0.55-2.28), and 1.86 (1.10-3.13) for PM(10) and 1.11 (0.93-1.32), 1.13 (0.86-1.50), and 1.23 (0.99-1.53) for nitrogen dioxide. For hemorrhagic stroke, the corresponding rate ratios were 0.52 (0.20-1.37), 0.78 (0.17-3.51), and 0.51 (0.12-2.22) for PM(10) and 0.86 (0.60-1.24), 1.12 (0.66-1.90), and 0.78 (0.44-1.39) for nitrogen dioxide. CONCLUSIONS: Although there was no significant association between outdoor air pollutants and ischemic stroke incidence for all ages combined, there was a suggestion of increased risk among people aged 65 to 79 years. There was no evidence of increased incidence in hemorrhagic stroke.

Impact of outdoor air pollution on survival after stroke: population-based cohort study.

BACKGROUND AND PURPOSE: The impact of air pollution on survival after stroke is unknown. We examined the impact of outdoor air pollution on stroke survival by studying a population-based cohort. METHODS: All patients who experienced their first-ever stroke between 1995 and 2005 in a geographically defined part of London, where road traffic contributes to spatial variation in air pollution, were followed up to mid-2006. Outdoor concentrations of nitrogen dioxide and particulate matter <10 microm in diameter modeled at a 20-m grid point resolution for 2002 were linked to residential postal codes. Hazard ratios were adjusted for age, sex, social class, ethnicity, smoking, alcohol consumption, prestroke functional ability, pre-existing medical conditions, stroke subtype and severity, hospital admission, and neighborhood socioeconomic deprivation. RESULTS: There were 1856 deaths among 3320 patients. Median survival was 3.7 years (interquartile range, 0.1 to 10.8). Mean exposure levels were 41 microg/m(3) (SD, 3.3; range, 32.2 to 103.2) for nitrogen dioxide and 25 microg/m(3) (SD, 1.3; range, 22.7 to 52) for particulate matter <10 microm in diameter. A 10-microg/m(3) increase in nitrogen dioxide was associated with a 28% (95% CI, 11% to 48%) increase in risk of death. A 10-microg/m(3) increase in particulate matter <10 mum in diameter was associated with a 52% (6% to 118%) increase in risk of death. Reduced survival was apparent throughout the follow-up period, ruling out short-term mortality displacement. CONCLUSIONS: Survival after stroke was lower among patients living in areas with higher levels of outdoor air pollution. If causal, a 10-microg/m(3) reduction in nitrogen dioxide exposure might be associated with a reduction in mortality comparable to that for stroke units. Improvements in outdoor air quality might contribute to better survival after stroke.

Socioeconomic deprivation, urban-rural location and alcohol-related mortality in England and Wales.

BACKGROUND: Many causes of death are directly attributable to the toxic effects of alcohol and deaths from these causes are increasing in the United Kingdom. The aim of this study was to investigate variation in alcohol-related mortality in relation to socioeconomic deprivation, urban-rural location and age within a national context. METHODS: An ecological study design was used with data from 8797 standard table wards in England and Wales. The methodology included using the Carstairs Index as a measure of socioeconomic deprivation at the small-area level and the national harmonised classification system for urban and rural areas in England and Wales. Alcohol-related mortality was defined using the National Statistics definition, devised for tracking national trends in alcohol-related deaths. Deaths from liver cirrhosis accounted for 85% of all deaths included in this definition. Deaths from 1999-2003 were examined and 2001 census ward population estimates were used as the denominators. RESULTS: The analysis was based on 28,839 deaths. Alcohol-related mortality rates were higher in men and increased with increasing age, generally reaching peak levels in middle-aged adults. The 45-64 year age group contained a quarter of the total population but accounted for half of all alcohol-related deaths. There was a clear association between alcohol-related mortality and socioeconomic deprivation, with progressively higher rates in more deprived areas. The strength of the association varied with age. Greatest relative inequalities were seen amongst people aged 25-44 years, with relative risks of 4.73 (95% CI 4.00 to 5.59) and 4.24 (95% CI 3.50 to 5.13) for men and women respectively in the most relative to the least deprived quintiles. People living in urban areas experienced higher alcohol-related mortality relative to those living in rural areas, with differences remaining after adjustment for socioeconomic deprivation. Adjusted relative risks for urban relative to rural areas were 1.35 (95% CI 1.20 to 1.52) and 1.13 (95% CI 1.01 to 1.25) for men and women respectively. CONCLUSIONS: Large inequalities in alcohol-related mortality exist between sub-groups of the population in England and Wales. These should be considered when designing public health policies to reduce alcohol-related harm.

Evaluation of the impact of a health forecast alert service on admissions for chronic obstructive pulmonary disease in Bradford and Airedale.

BACKGROUND: Chronic obstructive pulmonary disease (COPD) exacerbations are associated with adverse weather conditions. We examined if a forecasting alert service available to general practices in Bradford and Airedale for the winter of 2007-08 reduced COPD admissions. METHODS: We compared admissions in 2007-08 with 2006-07 when the service was not available. We examined admissions in December to March, and in the 7- and 14-day post-alert periods. There were five alerts in 2006-07 and four in 2007-08. We compared practices using the service to varying extents with practices not using it. RESULTS: Admission rate ratios for practices using the service were 0.98 [95% confidence interval (CI): 0.78-1.22] for December to March, and 0.82 (CI: 0.57-1.18) and 0.95 (CI: 0.72-1.26) for the 7- and 14-day post-alert periods, respectively. When we took into account the proportion of patients entered on the alerts system and the duration for which practices participated in the service, admission rate ratios for practices fully using the service were 1.11 (CI: 0.80-1.52), 1.22 (CI: 0.73-2.04) and 1.21 (CI: 0.82-1.78) for the three corresponding periods. CONCLUSION: We failed to show that any change in admissions associated with the forecasting service was significant. More research on the effectiveness of the COPD forecasting service is needed.

Do walk-in centres for commuters work? A mixed methods evaluation.

BACKGROUND: Between 2005 and 2007, six pilot walk-in centres were opened in or near train stations, to provide health care to commuters. They are run by independent providers on behalf of the NHS, providing access to doctors and nurses. AIM: To evaluate the policy of commuter walk-in centres. DESIGN OF STUDY: Mixed methods evaluation. SETTING: Six centres in England. METHOD: Site visits, interviews with 28 users, survey of 1828 users, economic estimates, and interviews with six commissioning managers. RESULTS: Each centre was located near a train station, although two were not within the main commuter flow. The average number of patients attending each centre on days when the user survey was undertaken was between 33 and 101 per day, considerably lower than the planned capacity of 150-180. Sixty-two per cent (1004/1627) of users identified themselves as commuters within the user survey, and 38% (95% confidence interval = 13% to 62%) had travelled to work by train that day. A large proportion of users worked in the local area (61%). The estimated cost per attendance, based on limited activity and price data, was between £52 and £150 for different centres at estimated current activity levels. Primary care trust managers' plans for the future of the centres involved changing the focus of the service to fit their local health economy. CONCLUSION: Pilot walk-in centres placed near train stations for commuters had low activity levels and high costs. A policy of placing healthcare centres in areas of high worker density may be more successful.

A method for modelling GP practice level deprivation scores using GIS.

BACKGROUND: A measure of general practice level socioeconomic deprivation can be used to explore the association between deprivation and other practice characteristics. An area-based categorisation is commonly chosen as the basis for such a deprivation measure. Ideally a practice population-weighted area-based deprivation score would be calculated using individual level spatially referenced data. However, these data are often unavailable. One approach is to link the practice postcode to an area-based deprivation score, but this method has limitations. This study aimed to develop a Geographical Information Systems (GIS) based model that could better predict a practice population-weighted deprivation score in the absence of patient level data than simple practice postcode linkage. RESULTS: We calculated predicted practice level Index of Multiple Deprivation (IMD) 2004 deprivation scores using two methods that did not require patient level data. Firstly we linked the practice postcode to an IMD 2004 score, and secondly we used a GIS model derived using data from Rotherham, UK. We compared our two sets of predicted scores to "gold standard" practice population-weighted scores for practices in Doncaster, Havering and Warrington. Overall, the practice postcode linkage method overestimated "gold standard" IMD scores by 2.54 points (95% CI 0.94, 4.14), whereas our modelling method showed no such bias (mean difference 0.36, 95% CI -0.30, 1.02). The postcode-linked method systematically underestimated the gold standard score in less deprived areas, and overestimated it in more deprived areas. Our modelling method showed a small underestimation in scores at higher levels of deprivation in Havering, but showed no bias in Doncaster or Warrington. The postcode-linked method showed more variability when predicting scores than did the GIS modelling method. CONCLUSION: A GIS based model can be used to predict a practice population-weighted area-based deprivation measure in the absence of patient level data. Our modelled measure generally had better agreement with the population-weighted measure than did a postcode-linked measure. Our model may also avoid an underestimation of IMD scores in less deprived areas, and overestimation of scores in more deprived areas, seen when using postcode linked scores. The proposed method may be of use to researchers who do not have access to patient level spatially referenced data.

Impact of NHS walk-in centres on primary care access times: ecological study.

OBJECTIVE: To examine whether walk-in centres contribute to shorter waiting times for a general practice appointment. DESIGN: Ecological study. SETTING: 2509 general practices in 56 primary care trusts in England; 32 walk-in centres within 3 km of one of these practices. MAIN OUTCOME MEASURE: Waiting time to next available general practitioner appointment (April 2003 to December 2004), from national monthly primary care access survey. RESULTS: The percentage of practices achieving the target waiting time of less than 48 hours to see a general practitioner increased from 67% to 87% over the 21 month study period (adjusted odds ratio 1.07 (95% confidence interval 1.06 to 1.08) per increase in month). Achievement of the waiting time target decreased with increasing multiple deprivation (0.57 (0.49 to 0.67) for most versus least deprived third) and increased with increasing practice population size (1.02 (1.00 to 1.04) per 1000 increase). No evidence was found that increasing distance from a walk-in centre was associated with decreasing odds of achieving the waiting time target (1.00 (0.99 to 1.01) per km increase). Increasing "exposure" to a walk-in centre, modelled with a distance decay function based on attendance rates, also showed little evidence of association with achievement of the waiting time target (1.02 (0.97 to 1.08) for interquartile range increase). No evidence existed that the rate of increase in achieving the 48 hour target over time was enhanced by proximity or "exposure" to a walk-in centre. Results were similar when the analysis was rerun with data for 2003 only (done because pressure in 2004 to meet the government's deadline might have led to other changes that could have masked any walk-in centre effect). CONCLUSIONS: No evidence existed that walk-in centres shortened waiting times for access to primary care, and the results do not support the use of walk-in centres for this purpose.

Outdoor NOx and stroke mortality: adjusting for small area level smoking prevalence using a Bayesian approach.

There is increasing evidence, mainly from daily time series studies, linking air pollution and stroke. Small area level geographical correlation studies offer another means of examining the air pollution-stroke association. Populations within small areas may be more homogeneous than those within larger areal units, and census-based socioeconomic information may be available to adjust for confounding effects. Data on smoking from health surveys may be incorporated in spatial analyses to adjust for potential confounding effects but may be sparse at the small area level. Smoothing, using data from neighbouring areas, may be used to increase the precision of smoking prevalence estimates for small areas. We examined the effect of modelled outdoor NOx levels on stroke mortality using a Bayesian hierarchical spatial model to incorporate random effects, in order to allow for unmeasured confounders and to acknowledge sampling error in the estimation of smoking prevalence. We observed an association between NOx and stroke mortality after taking into account random effects at the small area level. We found no association between smoking prevalence and stroke mortality at the small area level after modelling took into account imprecision in estimating smoking prevalence. The approach we used to incorporate smoking as a covariate in a single large model is conceptually sound, though it made little difference to the substantive results.