Chris Grundy

Effect of 20 mph traffic speed zones on road injuries in London, 1986-2006: controlled interrupted time series analysis

Objective To quantify the effect of the introduction of 20 mph (32 km an hour) traffic speed zones on road collisions, injuries, and fatalities in London. Design Observational study based on analysis of geographically coded police data on road casualties, 1986-2006. Analyses were made of longitudinal changes in counts of road injuries within each of 119 029 road segments with at least one casualty with conditional fixed effects Poisson models. Estimates of the effect of introducing 20 mph zones on casualties within those zones and in adjacent areas were adjusted for the underlying downward trend in traffic casualties. Setting London. Main outcome measures All casualties from road collisions; those killed and seriously injured (KSI). Results The introduction of 20 mph zones was associated with a 41.9% (95% confidence interval 36.0% to 47.8%) reduction in road casualties, after adjustment for underlying time trends. The percentage reduction was greatest in younger children and greater for the category of killed or seriously injured casualties than for minor injuries. There was no evidence of casualty migration to areas adjacent to 20 mph zones, where casualties also fell slightly by an average of 8.0% (4.4% to 11.5%). Conclusions 20 mph zones are effective measures for reducing road injuries and deaths.

An integrated tool to assess the role of new planting in PM10 capture and the human health benefits: a case study in London.

The role of vegetation in mitigating the effects of PM(10) pollution has been highlighted as one potential benefit of urban greenspace. An integrated modelling approach is presented which utilises air dispersion (ADMS-Urban) and particulate interception (UFORE) to predict the PM(10) concentrations both before and after greenspace establishment, using a 10 x 10 km area of East London Green Grid (ELGG) as a case study. The corresponding health benefits, in terms of premature mortality and respiratory hospital admissions, as a result of the reduced exposure of the local population are also modelled. PM(10) capture from the scenario comprising 75% grassland, 20% sycamore maple (Acer pseudoplatanus L.) and 5% Douglas fir (Pseudotsuga menziesii (Mirb.) Franco) was estimated to be 90.41 t yr(-1), equating to 0.009 t ha(-1) yr(-1) over the whole study area. The human health modelling estimated that 2 deaths and 2 hospital admissions would be averted per year.

Teenage conceptions, abortions, and births in England, 1994–2003, and the national teenage pregnancy strategy

BACKGROUND The aim of this study was to quantify the change in the number of conceptions and abortions among women younger than 18 years in England in relation to the governments national teenage pregnancy strategy. METHODS We undertook geographic analysis of data for 148 top-tier local authority areas. The main outcomes were changes in under-18 conceptions, abortions, and births between the 5-year period before implementation of the strategy (1994-98) and the period immediately after implementation (1999-2003). FINDINGS The number of teenage conceptions peaked in 1998, then declined after the implementation in 1999 of the teenage pregnancy strategy. Under-18 conception rates fell by an average of 2.0% (95% CI 1.8 to 2.2) per year between 1998 and 2003, below the rate needed to achieve the target of 50% reduction by 2010. The net change between 1994-98 and 1999-2003 was a fall in conceptions of 3.2% (2.6 to 3.9) or 1.4 per 1000 women aged 15-17 years, a rise in abortions of 7.5% (6.5 to 8.6) or 1.4 per 1000, and a fall in births of 10.6% (9.9 to 11.3) or 2.8 per 1000. The change in the number of conceptions was greater in deprived and more rural areas, and in those with lower educational attainment. The change was greater in areas where services and access to them were poorer, but greater where more strategy-related resources had been targeted. INTERPRETATION The decline in under-18 conception and birth rates since 1998 and evidence that the declines have been greatest in areas receiving higher amounts of strategy-related funding provides limited evidence of the effect of Englands national teenage pregnancy strategy. The full effect of local prevention will be clear only with longer observation, and substantial further progress is needed to remedy Englands historically poor international position in teenage conceptions.

Serious injuries in children: variations by area deprivation and settlement type

Objective: To examine the variation in serious injuries in children by the level of deprivation in an area and by types of settlement. Methods: Hospital admission rates for serious injury to children aged 0–15 years in census lower super output areas in England during the 5-year period 1 April 1999 to 31 March 2004 were analysed. Results: Rates of serious injury in children were higher in the most deprived areas than in the least deprived for pedestrians (rate ratio (RR) 4.1; 95% CI 2.8 to 6.0) and cyclists (RR 3.0; 95% CI 1.9 to 4.7). Rates of serious pedestrian injury were lower in towns and fringe areas (RR 0.67; 95% CI 0.53 to 0.86) and in village (RR 0.64; 95% CI 0.50 to 0.83) areas than in urban areas. The rate of serious injury to cyclists was lower in London than other urban areas (RR 0.78; 95% CI 0.62 to 0.98). The rate of serious injury to car occupants was higher in village than urban areas (RR 1.51; 95% CI 1.05 to 2.17). Rates of serious injury caused by falls were higher in London (RR 1.60; 95% CI 1.47 to 1.75) and lower in villages (RR 0.76; 95% CI 0.66 to 0.88) than in urban areas. Steeper socio-economic gradients in serious injury rates were identified in rural areas for cyclists and for children suffering falls. Conclusions: Socio-economic inequalities in serious injury exist across the whole of England, particularly for child pedestrians. Rates of serious injury vary by settlement type, and inequalities vary by cause of injury between rural and urban settings.

Validity and feasibility of a satellite imagery-based method for rapid estimation of displaced populations

BackgroundEstimating the size of forcibly displaced populations is key to documenting their plight and allocating sufficient resources to their assistance, but is often not done, particularly during the acute phase of displacement, due to methodological challenges and inaccessibility. In this study, we explored the potential use of very high resolution satellite imagery to remotely estimate forcibly displaced populations.MethodsOur method consisted of multiplying (i) manual counts of assumed residential structures on a satellite image and (ii) estimates of the mean number of people per structure (structure occupancy) obtained from publicly available reports. We computed population estimates for 11 sites in Bangladesh, Chad, Democratic Republic of Congo, Ethiopia, Haiti, Kenya and Mozambique (six refugee camps, three internally displaced persons’ camps and two urban neighbourhoods with a mixture of residents and displaced) ranging in population from 1,969 to 90,547, and compared these to “gold standard” reference population figures from census or other robust methods.ResultsStructure counts by independent analysts were reasonably consistent. Between one and 11 occupancy reports were available per site and most of these reported people per household rather than per structure. The imagery-based method had a precision relative to reference population figures of <10% in four sites and 10–30% in three sites, but severely over-estimated the population in an Ethiopian camp with implausible occupancy data and two post-earthquake Haiti sites featuring dense and complex residential layout. For each site, estimates were produced in 2–5 working person-days.ConclusionsIn settings with clearly distinguishable individual structures, the remote, imagery-based method had reasonable accuracy for the purposes of rapid estimation, was simple and quick to implement, and would likely perform better in more current application. However, it may have insurmountable limitations in settings featuring connected buildings or shelters, a complex pattern of roofs and multi-level buildings. Based on these results, we discuss possible ways forward for the method’s development.

Impact and uncertainty of a traffic management intervention: Population exposure to polycyclic aromatic hydrocarbons

In urban areas, road traffic is a major source of carcinogenic polycyclic aromatic hydrocarbons (PAH), thus any changes in traffic patterns are expected to affect PAH concentrations in ambient air. Exposure to PAH and other traffic-related air pollutants has often been quantified in a deterministic manner that disregards the various sources of uncertainty in the modelling systems used. In this study, we developed a generic method for handling uncertainty in population exposure models. The method was applied to quantify the uncertainty in population exposure to benzo[a]pyrene (BaP) before and after the implementation of a traffic management intervention. This intervention would affect the movement of vehicles in the studied area and consequently alter traffic emissions, pollutant concentrations and population exposure. Several models, including an emission calculator, a dispersion model and a Geographic Information System were used to quantify the impact of the traffic management intervention. We established four exposure zones defined by distance of residence postcode centroids from major road or intersection. A stochastic method was used to quantify the uncertainty in the population exposure model. The method characterises uncertainty using probability measures and propagates it applying Monte Carlo analysis. The overall model predicted that the traffic management scheme would lead to a minor reduction in mean population exposure to BaP in the studied area. However, the uncertainty associated with the exposure estimates was much larger than this reduction. The proposed method is generic and provides realistic estimates of population exposure to traffic-related pollutants, as well as characterises the uncertainty in these estimates. This method can be used within a decision support tool to evaluate the impact of alternative traffic management policies.

The effect of reduced street lighting on road casualties and crime in England and Wales: controlled interrupted time series analysis

Background Many local authorities in England and Wales have reduced street lighting at night to save money and reduce carbon emissions. There is no evidence to date on whether these reductions impact on public health. We quantified the effect of 4 street lighting adaptation strategies (switch off, part-night lighting, dimming and white light) on casualties and crime in England and Wales. Methods Observational study based on analysis of geographically coded police data on road traffic collisions and crime in 62 local authorities. Conditional Poisson models were used to analyse longitudinal changes in the counts of night-time collisions occurring on affected roads during 2000–2013, and crime within census Middle Super Output Areas during 2010–2013. Effect estimates were adjusted for regional temporal trends in casualties and crime. Results There was no evidence that any street lighting adaptation strategy was associated with a change in collisions at night. There was significant statistical heterogeneity in the effects on crime estimated at police force level. Overall, there was no evidence for an association between the aggregate count of crime and switch off (RR 0.11; 95% CI 0.01 to 2.75) or part-night lighting (RR 0.96; 95% CI 0.86 to 1.06). There was weak evidence for a reduction in the aggregate count of crime and dimming (RR 0.84; 95% CI 0.70 to 1.02) and white light (RR 0.89; 95% CI 0.77 to 1.03). Conclusions This study found little evidence of harmful effects of switch off, part-night lighting, dimming, or changes to white light/LEDs on road collisions or crime in England and Wales.

Evidence for Community Transmission of Community-Associated but Not Health-Care-Associated Methicillin-Resistant Staphylococcus Aureus Strains Linked to Social and Material Deprivation: Spatial Analysis of Cross-sectional Data

Background Identifying and tackling the social determinants of infectious diseases has become a public health priority following the recognition that individuals with lower socioeconomic status are disproportionately affected by infectious diseases. In many parts of the world, epidemiologically and genotypically defined community-associated (CA) methicillin-resistant Staphylococcus aureus (MRSA) strains have emerged to become frequent causes of hospital infection. The aim of this study was to use spatial models with adjustment for area-level hospital attendance to determine the transmission niche of genotypically defined CA- and health-care-associated (HA)-MRSA strains across a diverse region of South East London and to explore a potential link between MRSA carriage and markers of social and material deprivation. Methods and Findings This study involved spatial analysis of cross-sectional data linked with all MRSA isolates identified by three National Health Service (NHS) microbiology laboratories between 1 November 2011 and 29 February 2012. The cohort of hospital-based NHS microbiology diagnostic services serves 867,254 usual residents in the Lambeth, Southwark, and Lewisham boroughs in South East London, United Kingdom (UK). Isolates were classified as HA- or CA-MRSA based on whole genome sequencing. All MRSA cases identified over 4 mo within the three-borough catchment area (n = 471) were mapped to small geographies and linked to area-level aggregated socioeconomic and demographic data. Disease mapping and ecological regression models were used to infer the most likely transmission niches for each MRSA genetic classification and to describe the spatial epidemiology of MRSA in relation to social determinants. Specifically, we aimed to identify demographic and socioeconomic population traits that explain cross-area extra variation in HA- and CA-MRSA relative risks following adjustment for hospital attendance data. We explored the potential for associations with the English Indices of Deprivation 2010 (including the Index of Multiple Deprivation and several deprivation domains and subdomains) and the 2011 England and Wales census demographic and socioeconomic indicators (including numbers of households by deprivation dimension) and indicators of population health. Both CA-and HA-MRSA were associated with household deprivation (CA-MRSA relative risk [RR]: 1.72 [1.03–2.94]; HA-MRSA RR: 1.57 [1.06–2.33]), which was correlated with hospital attendance (Pearson correlation coefficient [PCC] = 0.76). HA-MRSA was also associated with poor health (RR: 1.10 [1.01–1.19]) and residence in communal care homes (RR: 1.24 [1.12–1.37]), whereas CA-MRSA was linked with household overcrowding (RR: 1.58 [1.04–2.41]) and wider barriers, which represent a combined score for household overcrowding, low income, and homelessness (RR: 1.76 [1.16–2.70]). CA-MRSA was also associated with recent immigration to the UK (RR: 1.77 [1.19–2.66]). For the area-level variation in RR for CA-MRSA, 28.67% was attributable to the spatial arrangement of target geographies, compared with only 0.09% for HA-MRSA. An advantage to our study is that it provided a representative sample of usual residents receiving care in the catchment areas. A limitation is that relationships apparent in aggregated data analyses cannot be assumed to operate at the individual level. Conclusions There was no evidence of community transmission of HA-MRSA strains, implying that HA-MRSA cases identified in the community originate from the hospital reservoir and are maintained by frequent attendance at health care facilities. In contrast, there was a high risk of CA-MRSA in deprived areas linked with overcrowding, homelessness, low income, and recent immigration to the UK, which was not explainable by health care exposure. Furthermore, areas adjacent to these deprived areas were themselves at greater risk of CA-MRSA, indicating community transmission of CA-MRSA. This ongoing community transmission could lead to CA-MRSA becoming the dominant strain types carried by patients admitted to hospital, particularly if successful hospital-based MRSA infection control programmes are maintained. These results suggest that community infection control programmes targeting transmission of CA-MRSA will be required to control MRSA in both the community and hospital. These epidemiological changes will also have implications for effectiveness of risk-factor-based hospital admission MRSA screening programmes.

The impact of 20 mph traffic speed zones on inequalities in road casualties in London

Background Road traffic casualties show some of the widest socioeconomic differentials of any cause of morbidity or mortality, and as yet there is little evidence on what works to reduce them. This study quantified the current and potential future impact of the introduction of 20 mph zones on socioeconomic inequalities in road casualties in London. Methods An observational study based on analysis of geographically coded police road casualties data, 1987–2006. Changes in counts of casualties from road collisions, those killed and seriously injured and pedestrian injuries by quintile of deprivation were calculated. Results The effect of 20 mph zones was similar across quintiles of socioeconomic deprivation, being associated with a 41.8% (95% CI 21.0% to 62.6%) decline in casualties in areas in the least deprived quintile versus 38.3% (31.5% to 45.0%) in the most deprived quintile. Because of the greater number of road casualties in deprived areas and the targeting of zones to such areas, the number of casualties prevented by zones was substantially larger in areas of greater socioeconomic deprivation. However, the underlying decline in road casualties on all roads was appreciably greater in less deprived areas (p<0.001 for trend) so that despite the targeting of 20 mph zones, socioeconomic inequalities in road injuries in London have widened over time. Extending 20 mph schemes has only limited the potential to reduce differentials further. Conclusions The implementation of 20 mph zones targeted at deprived areas has mitigated widening socioeconomic differentials in road injury in London and to some degree narrowed them, but there is limited potential for further gain.

A qualitative geographical information systems approach to explore how older people over 70 years interact with and define their neighbourhood environment.

A growing body of literature explores the relationship between the built environment and health, and the methodological challenges of understanding these complex interactions across the lifecourse. The impact of the neighbourhood environment on health and behaviour amongst older adults has received less attention, despite this age group being potentially more vulnerable to barriers in their surrounding social and physical environment. A qualitative geographical information systems (QGIS) approach was taken to facilitate the understanding of how older people over 70 in 5 UK towns interact with their local neighbourhood. The concept of neighbourhood changed seasonally and over the lifecourse, and was associated with social factors such as friends, family, or community activities, rather than places. Spaces stretched further than the local, which is problematic for older people who rely on variable public transport provision. QGIS techniques prompted rich discussions on interactions with and the meanings of ‘place’ in older people.