Huw Williams

Modeling Discrete Choices in the Presence of Inertia and Serial Correlation

The concept of habit or inertia in the context of (reluctance to) change in travel behavior has an important bearing on transport policy (e.g., how to break car use habits) and has remained an unresolved issue in demand modeling. Another major problem in modeling the response to policy measures is the potential correlation or dependence between the choices made by a given individual over time (i.e., serial correlation). The two phenomena are closely related. This paper discusses the effects of considering inertia and serial correlation on travel choices. We formulate a fairly general discrete choice model that incorporates randomly distributed inertia thresholds and allow for serial correlation. The inertia thresholds may also be a function of an individuals socioeconomic characteristics and choice conditions. The model can be applied with panel data as well as with mixed revealed and stated preference data. We applied it to real and simulated data, confirming that if these phenomena exist in the population but are not considered, serious errors in model estimation and prediction may arise, especially in the case of large policy impacts.

Urban-rural mortality differentials: controlling for material deprivation.

This paper investigates the relationship between premature mortality and material deprivation, and the differences in this relationship between urban and rural areas. We examine, given comparable measures of affluence or deprivation, whether residual differences exist between urban and rural areas for all-causes of death and, separately, for cancers, circulatory and respiratory diseases. Using 1990-92 mortality data for the 908 wards of Wales we apply statistical analyses based on tabular data and parametric Poisson regression models. Contrasts are sought between six urban and rural categories defined in terms of settlement sizes and the employment structure of rural areas. Inequalities in all-cause premature mortality are widest in the cities, narrowest in the deeper rural areas, and of intermediate and comparable value in other areas of Wales. This is largely a reflection of the different distributions of material deprivation in these areas. After controlling for differences in socio-economic characteristics, using deprivation measures, the tendency for lower mortality in deeper rural areas is substantially reduced. Residual mortality differences between urban and rural areas are shown to be dependent on the way deprivation is measured and the disease group under study. For cancers there are no residual mortality differences, while for respiratory and circulatory diseases some of the residual variation can be accounted for by employment variables, particularly previous employment in the coal mining industry.

Spatial and temporal variation of mortality and deprivation. 1: widening health inequalities.

In this paper we examine the relationship between premature mortality and material deprivation both over time (the intercensal period, 1981–91) and over space (for the population in wards and ward groups in Wales). Our focus is on the methods of analysis for small area (ward-based) multiple cross-section mortality data and their application to the substantive issue of the persistent and widening inequalities in Wales. In this paper we examine all-cause deaths and mortality by specific disease classes for groups (quintiles) of wards ranked according to standard measures of material deprivation. Although there have been reductions in premature mortality across all deprivation groups in Wales, over the decade, the gap has widened between the most and least deprived areas. Mortality decline in the largest disease category (circulatory) was found to be significantly lower in the most deprived quintile of wards than in the rest of Wales. Compared with results from the North of England, mortality decline in Wales has been rather greater.

Application of willingness-to-pay methods to value transport externalities in less developed countries

In this paper we report on two applications of the willingness-to-pay (WTP) approach to valuing transport externalities in Santiago, Chile. The first involves a contingent valuation study of mortality risk due in part to pollution-related causes, and the second, a stated preference study for valuing the reduction of risk from road fatalities. It is concluded that the approaches, and particularly that based on stated choice methods, offer practical and consistent methods of establishing unit values in higher-income developing countries. The unit values derived from the WTP methods appear to justify a greater allocation of resources to safety and pollution countermeasures compared with those derived from more traditional approaches.

Safety incidents in the primary care office setting

BACKGROUND: In the United Kingdom, 26% of child deaths have identifiable failures in care. Although children account for 40% of family physicians’ workload, little is known about the safety of care in the community setting. Using data from a national patient safety incident reporting system, this study aimed to characterize the pediatric safety incidents occurring in family practice. METHODS: We undertook a retrospective, cross-sectional, mixed methods study of pediatric reports submitted to the UK National Reporting and Learning System from family practice. Analysis involved detailed data coding using multiaxial frameworks, descriptive statistical analysis, and thematic analysis of a special-case sample of reports. Using frequency distributions and cross-tabulations, the relationships between incident types and contributory factors were explored. RESULTS: Of 1788 reports identified, 763 (42.7%) described harm to children. Three crosscutting priority areas were identified: medication management, assessment and referral, and treatment. The 4 incident types associated with the most harmful outcomes are errors associated with diagnosis and assessment, delivery of treatment and procedures, referrals, and medication provision. Poor referral and treatment decisions in severely unwell or vulnerable children, along with delayed diagnosis and insufficient assessment of such children, featured prominently in incidents resulting in severe harm or death. CONCLUSION: This is the first analysis of nationally collected, family practice–related pediatric safety incident reports. Recommendations to mitigate harm in these priority areas include mandatory pediatric training for all family physicians; use of electronic tools to support diagnosis, management, and referral decision-making; and use of technological adjuncts such as barcode scanning to reduce medication errors.

Interaction between cigarettes and propranolol in treatment of angina pectoris.

To determine whether cigarette smoking interferes with the medical management of angina pectoris, 10 patients with angina pectoris who smoked at least 10 cigarettes a day were studied before, during, and after a standardised maximal exercise test. This was done at the end of four randomly allocated one-week treatment periods during which the patients took glyceryl trinitrate while not smoking, took glyceryl trinitrate while smoking, took glycerly trinitrate and propranolol (380 mg/day) while not smoking, and took glyceryl trinitrate and propranolol while smoking. Carboxyhaemoglobin was measured to ensure compliance. Smoking was associated with a significantly higher heart rate, blood pressure, number of positions with ST-segment depression, and total ST-segment depression after exercise than non-smoking (p < 0.01) whether or not the patients were taking propranolol. These results suggest that smoking aggravates the simple haemodynamic variables used to assess myocardial oxygen requirements and the exercise-induced precordial electrocardiographic signs of myocardial ischaemia. These effects were still evident after treatment with propranolol and represent a hindrance to the effective medical treatment of angina pectoris.

Harms from discharge to primary care: mixed methods analysis of incident reports

Background Discharge from hospital presents significant risks to patient safety, with up to one in five patients experiencing adverse events within 3 weeks of leaving hospital. Aim To describe the frequency and types of patient safety incidents associated with discharge from secondary to primary care, and commonly described contributory factors to identify recommendations for practice. Design and setting A mixed methods analysis of 598 patient safety incident reports in England and Wales related to ‘Discharge’ from the National Reporting and Learning System. Method Detailed data coding (with 20% double-coding), data summaries generated using descriptive statistical analysis, and thematic analysis of special-case sample of reports. Incident type, contributory factors, type, and level of harm were described, informing recommendations for future practice. Results A total of 598 eligible reports were analysed. The four main themes were: errors in discharge communication (n = 151; 54% causing harm); errors in referrals to community care (n = 136; 73% causing harm); errors in medication (n = 97; 87% causing harm); and lack of provision of care adjuncts such as dressings (n = 62; 94% causing harm). Common contributory factors were staff factors (not following referral protocols); and organisational factors (lack of clear guidelines or inefficient processes). Improvement opportunities include developing and testing electronic discharge methods with agreed minimum information requirements and unified referrals systems to community care providers; and promoting a safety culture with ‘safe discharge’ checklists, discharge coordinators, and family involvement. Conclusion Significant harm was evident due to deficits in the discharge process. Interventions in this area need to be evaluated and learning shared widely.

Spatial and temporal variation of mortality and deprivation 2: statistical modelling.

Building on the tabular analyses exemplified in our first paper and widely used in the medical literature, we use generalised linear models to provide a formal, statistical approach to the analysis of mortality and deprivation relationships, and their change over time. Three types of fixed effects model are specified and estimated with the same ward-level data sets for Wales examined in our first paper. They are: Poisson models for analysing mortality and deprivation at a single cross section in time; repeated-measures Poisson models for analysing mortality–deprivation relations, not only at cross sections in time, but also their changes over time; and logit models focusing on temporal changes in mortality–deprivation relationships. Nonlinear effects of deprivation on mortality have been explored by using dummy variables representing deprivation categories to establish the connection between formal statistical models and the tabular approach.

A cross-sectional mixed methods study protocol to generate learning from patient safety incidents reported from general practice

Introduction Incident reports contain descriptions of errors and harms that occurred during clinical care delivery. Few observational studies have characterised incidents from general practice, and none of these have been from the England and Wales National Reporting and Learning System. This study aims to describe incidents reported from a general practice care setting. Methods and analysis A general practice patient safety incident classification will be developed to characterise patient safety incidents. A weighted-random sample of 12 500 incidents describing no harm, low harm and moderate harm of patients, and all incidents describing severe harm and death of patients will be classified. Insights from exploratory descriptive statistics and thematic analysis will be combined to identify priority areas for future interventions. Ethics and dissemination The need for ethical approval was waivered by the Aneurin Bevan University Health Board research risk review committee given the anonymised nature of data (ABHB R&D Ref number: SA/410/13). The authors will submit the results of the study to relevant journals and undertake national and international oral presentations to researchers, clinicians and policymakers.

Sources of unsafe primary care for older adults: a mixed-methods analysis of patient safety incident reports

Background older adults are frequent users of primary healthcare services, but are at increased risk of healthcare-related harm in this setting. Objectives to describe the factors associated with actual or potential harm to patients aged 65 years and older, treated in primary care, to identify action to produce safer care. Design and Setting a cross-sectional mixed-methods analysis of a national (England and Wales) database of patient safety incident reports from 2005 to 2013. Subjects 1,591 primary care patient safety incident reports regarding patients aged 65 years and older. Methods we developed a classification system for the analysis of patient safety incident reports to describe: the incident and preceding chain of incidents; other contributory factors; and patient harm outcome. We combined findings from exploratory descriptive and thematic analyses to identify key sources of unsafe care. Results the main sources of unsafe care in our weighted sample were due to: medication-related incidents e.g. prescribing, dispensing and administering (n = 486, 31%; 15% serious patient harm); communication-related incidents e.g. incomplete or non-transfer of information across care boundaries (n = 390, 25%; 12% serious patient harm); and clinical decision-making incidents which led to the most serious patient harm outcomes (n = 203, 13%; 41% serious patient harm). Conclusion priority areas for further research to determine the burden and preventability of unsafe primary care for older adults, include: the timely electronic tools for prescribing, dispensing and administering medication in the community; electronic transfer of information between healthcare settings; and, better clinical decision-making support and guidance.