Michael Keall

THE INFLUENCE OF ALCOHOL, AGE AND NUMBER OF PASSENGERS ON THE NIGHT-TIME RISK OF DRIVER FATAL INJURY IN NEW ZEALAND

Breath alcohol measurements and other data collected at randomly selected roadside sites were combined with data on fatally injured drivers in crashes occurring on the same weekdays and times (Friday and Saturday nights) at locations matched by the size of the nearest town. A logistic model was fitted to these data for the years 1995-2000 to estimate the effects of alcohol, drivers age and the influence of passengers carried on the risk of driver fatal injury in New Zealand. The estimated risks increased steeply with increasing blood alcohol concentration (BAC), closely following an exponential curve at levels below about 200mg/dl (i.e. 0.2%) and increasing less than exponentially thereon. The model fitted to data for drivers under 200mg/dl showed that risks at all BAC levels were statistically significantly higher for drivers aged under 20 (over five times) and for drivers aged 20-29 (three times) than for drivers aged 30 and over. Further, controlling for age and BAC level, driving with a single passenger was associated with approximately half the night-time risk of driver fatal injury relative to driving either solo or with two or more passengers. According to a recent travel survey, the types of passengers carried at the times of night and days of week studied appear to differ significantly from the types of passengers carried generally, which may lead to different passenger effects on driver behaviour. The high relative risk of teenage drivers means that they reach high risk levels commonly regarded as unacceptable in the field of road safety even at their current legal limit of 30mg/dl, particularly when more than one passenger is carried in the car.

Increasing incidence of serious infectious diseases and inequalities in New Zealand: a national epidemiological study.

BACKGROUND Although the burden of infectious diseases seems to be decreasing in developed countries, few national studies have measured the total incidence of these diseases. We aimed to develop and apply a robust systematic method for monitoring the epidemiology of serious infectious diseases. METHODS We did a national epidemiological study with all hospital admissions for infectious and non-infectious diseases in New Zealand from 1989 to 2008, to investigate trends in incidence and distribution by ethnic group and socioeconomic status. We extended a recoding system based on the ninth revision of international classification of diseases (ICD-9) to the tenth revision (ICD-10), and applied this to data for hospital admissions from the New Zealand Ministry of Health, National Minimum Dataset. We filtered results to account for changes in health-care practices over time. Acute overnight admissions were the events of interest. FINDINGS Infectious diseases made the largest contribution to hospital admissions of any cause. Their contribution increased from 20·5% of acute admissions in 1989-93, to 26·6% in 2004-08. We noted clear ethnic and social inequalities in infectious disease risk. In 2004-08, the age-standardised rate ratio was 2·15 (95% CI 2·14-2·16) for Māori (indigenous New Zealanders) and 2·35 (2·34-2·37) for Pacific peoples compared with the European and other group. The ratio was 2·81 (2·80-2·83) for the most socioeconomically deprived quintile compared with the least deprived quintile. These inequalities have increased substantially in the past 20 years, particularly for Māori and Pacific peoples in the most deprived quintile. INTERPRETATION These findings support the need for stronger prevention efforts for infectious diseases, and reinforce the need to reduce ethnic and social inequalities and to address disparities in broad social determinants such as income levels, housing conditions, and access to health services. Our method could be adapted for infectious disease surveillance in other countries. FUNDING New Zealand Ministry of Health, New Zealand Health Research Council.

Older driver crash rates in relation to type and quantity of travel

It is a well-established phenomenon that, notwithstanding their overall good crash record, older drivers have a higher than average rate of involvement in injury crashes when the rate is calculated by dividing crash numbers by distance driven. It has been hypothesised that at least some of this higher crash rate is an artefact of the different nature of driving undertaken by many older drivers. For example, driving in congested urban environments provides more opportunities for collisions than driving the same distance on a motorway. However, there have been few opportunities to investigate this theory, as relevant data are difficult to acquire. High-quality data from the New Zealand Travel Survey (1997/1998) were combined with crash data to enable a statistical model to estimate the risk of driver groups under various driving conditions characterised by the type of road used, time of day, day of week, and season of year. Despite elevated crash risks per distance driven compared with middle-aged drivers for most road types, older drivers were as safe as any other age group when driving on motorways. Accounting for the fragility of older drivers and their passengers in the risk estimates for other road types, older drivers appeared to have daytime risks comparable to 25-year-olds and night-time risks as low as any other age group. The driving patterns of older drivers (in terms of when and where they drive) were estimated to minimize their risks in comparison with the driving patterns of other age groups. These results are of interest to both policy makers and transportation planners working against the background of inevitable increases in the number of older drivers as the population ages.

Home modifications to reduce injuries from falls in the Home Injury Prevention Intervention (HIPI) study: a cluster-randomised controlled trial

BACKGROUND Despite the considerable injury burden attributable to falls at home among the general population, few effective safety interventions have been identified. We tested the safety benefits of home modifications, including handrails for outside steps and internal stairs, grab rails for bathrooms, outside lighting, edging for outside steps, and slip-resistant surfacing for outside areas such as decks and porches. METHODS We did a single-blind, cluster-randomised controlled trial of households from the Taranaki region of New Zealand. To be eligible, participants had to live in an owner-occupied dwelling constructed before 1980 and at least one member of every household had to be in receipt of state benefits or subsidies. We randomly assigned households by electronic coin toss to either immediate home modifications (treatment group) or a 3-year wait before modifications (control group). Household members in the treatment group could not be masked to their assigned status because modifications were made to their homes. The primary outcome was the rate of falls at home per person per year that needed medical treatment, which we derived from administrative data for insurance claims. Coders who were unaware of the random allocation analysed text descriptions of injuries and coded injuries as all falls and injuries most likely to be affected by the home modifications tested. To account for clustering at the household level, we analysed all injuries from falls at home per person-year with a negative binomial generalised linear model with generalised estimating equations. Analysis was by intention to treat. This trial is registered with the Australian New Zealand Clinical Trials Registry, number ACTRN12609000779279. FINDINGS Of 842 households recruited, 436 (n=950 individual occupants) were randomly assigned to the treatment group and 406 (n=898 occupants) were allocated to the control group. After a median observation period of 1148 days (IQR 1085-1263), the crude rate of fall injuries per person per year was 0.061 in the treatment group and 0.072 in the control group (relative rate 0.86, 95% CI 0.66-1.12). The crude rate of injuries specific to the intervention per person per year was 0.018 in the treatment group and 0.028 in the control group (0.66, 0.43-1.00). A 26% reduction in the rate of injuries caused by falls at home per year exposed to the intervention was estimated in people allocated to the treatment group compared with those assigned to the control group, after adjustment for age, previous falls, sex, and ethnic origin (relative rate 0.74, 95% CI 0.58-0.94). Injuries specific to the home-modification intervention were cut by 39% per year exposed (0.61, 0.41-0.91). INTERPRETATION Our findings suggest that low-cost home modifications and repairs can be a means to reduce injury in the general population. Further research is needed to identify the effectiveness of particular modifications from the package tested. FUNDING Health Research Council of New Zealand.

Effectiveness of low speed autonomous emergency braking in real-world rear-end crashes

This study set out to evaluate the effectiveness of low speed autonomous emergency braking (AEB) technology in current model passenger vehicles, based on real-world crash experience. The validating vehicle safety through meta-analysis (VVSMA) group comprising a collaboration of government, industry consumer organisations and researchers, pooled data from a number of countries using a standard analysis format and the established MUND approach. Induced exposure methods were adopted to control for any extraneous effects. The findings showed a 38 percent overall reduction in rear-end crashes for vehicles fitted with AEB compared to a comparison sample of similar vehicles. There was no statistical evidence of any difference in effect between urban (≤60 km/h) and rural (>60 km/h) speed zones. Areas requiring further research were identified and widespread fitment through the vehicle fleet is recommended.

Association between the number of home injury hazards and home injury.

Although the home is a major setting for injury morbidity and mortality, there are few proven effective interventions for reducing home injury risk. To inform future research or interventions, this study measures associations between home injury hazards and home injury from a sample of New Zealand households. Logistic regression was used to assess the association between injury hazards identified by a building inspection and injuries requiring medical or associated services that occurred to household members prior to the inspection. There was an estimated increase of 22% in the odds of injury occurrence associated with each additional injury hazard found in the home (with 95% CI: 6-41%). This research suggests that addressing injury hazards in the home may be effective in reducing home injury. There are a number of potentially confounding factors that may affect relationships found between the existence of home hazards and injury occurrence. These need to be taken into account when future evaluations are planned.

Assessing housing quality and its impact on health, safety and sustainability

Background The adverse health and environmental effects of poor housing quality are well established. A central requirement for evidence-based policies and programmes to improve housing standards is a valid, reliable and practical way of measuring housing quality that is supported by policy agencies, the housing sector, researchers and the public. Methods This paper provides guidance on the development of housing quality-assessment tools that link practical measures of housing conditions to their effects on health, safety and sustainability, with particular reference to tools developed in New Zealand and England. Results The authors describe how information on housing quality can support individuals, agencies and the private sector to make worthwhile improvements to the health, safety and sustainability of housing. The information gathered and the resultant tools developed should be guided by the multiple purposes and end users of this information. Other important issues outlined include deciding on the scope, detailed content, practical administration issues and how the information will be analysed and summarised for its intended end users. There are likely to be considerable benefits from increased international collaboration and standardisation of approaches to measuring housing hazards. At the same time, these assessment approaches need to consider local factors such as climate, geography, culture, predominating building practices, important housing-related health issues and existing building codes. Conclusions An effective housing quality-assessment tool has a central role in supporting improvements to housing. The issues discussed in this paper are designed to motivate and assist the development of such tools.

Association between older driver characteristics, on-road driving test performance, and crash liability.

From May 1999, a new system for licensing older drivers was introduced in New Zealand. It included a practical on-road driving test with expanded scope, to be completed every two years from the time the driver turns 80. The relationship between crashes and test performance needed to be studied to inform the debate regarding the testing system. The population studied was all drivers who entered this licensing system during its first three years of operation. They were defined as crash involved if they were involved in an injury crash during the two years following their first licensure under the new system. Logistic regression was used to describe the risk of crash involvement in terms of driving test performance and other driver characteristics. Each driving test failure was associated with a 33% increase in the odds of crash involvement (95% CI 14% to 55%), controlling for age, gender, minor traffic violations, and whether the older driver lived with another licensed driver or not. Minor traffic violations in the two years following the driving test were associated with twice the odds of crash involvement. These results suggest that the new on-road driving test does identify older driver behaviors or limitations that are related to crash liability. It is anticipated that the results presented here will provide essential information for discussing older driver licensing systems, whose impact will grow in importance as the population of drivers ages.

THE EFFECT OF INCREASING RURAL INTERSTATE SPEED LIMITS IN THE UNITED STATES

Within a year of the repeal of the National Maximum Speed Limit in the United States, 23 states had raised their rural interstate speed limits to 70 or 75 mph. The effect on rural interstate fatalities was examined by modeling fatalities between 1992 and 1999 against the size of the new speed limit (no change, 70 mph, and 75 mph), the period before and after the speed limit change (1992 to 1995 vs. 1996 to 1999), and their interaction. Fatalities in the groups of states that raised their speed limits to 75 mph and 70 mph were 38% and 35%, respectively, higher than expected based on fatalities in the states that did not change their speed limits. Furthermore, the states that raised their speed limits to 75 mph had a higher rural interstate fatality rate before the speed limit was changed than the other groups of states.

Pedestrian exposure and the risk of child pedestrian injury

The authors used data from the New Zealand Household Travel Survey to examine the extent to which childrens pedestrian exposure varies with age, sex and household income. Pedestrian injury morbidity data were combined with pedestrian exposure data to examine age‐specific pedestrian injury risk. The annual number of road crossings for girls was greater than that for boys. Pedestrian exposure increased with increasing age. Children aged 5‐9 years in the lowest household income bracket crossed approximately 50% more roads than those in the middle and upper income brackets. However, for children aged 10‐14 years there was little variation with household income. Sex differences in pedestrian injury rates cannot be explained by differences in exposure although increased exposure may partly explain the increased injury rates for children in lower socio‐economic groups. Prevention strategies might aim to reduce pedestrian exposure or alternatively to reduce pedestrian injury risk per unit of exposure by making safer urban living environments.