Fred W. Johnson

NEIGHBORHOOD CHARACTERISTICS OF ALCOHOL-RELATED PEDESTRIAN INJURY COLLISIONS: A GEOSTATISTICAL ANALYSIS

This study conducted a geostatistical analysis of ecological data to examine the relationships of neighborhood characteristics, including alcohol availability and alcohol consumption patterns to pedestrian injury collisions. The central research question asked whether it was possible to identify unique neighborhood characteristics related to alcohol- and non–alcohol-involved pedestrian injuries. It was hypothesized that greater numbers of alcohol-involved pedestrian injuries would be observed in areas with greater concentrations of alcohol outlets, even after adjusting for socioeconomic characteristics, environmental factors, and drinking patterns of neighborhood residents. It was also hypothesized that independent of drinking patterns and alcohol availability, greater numbers of pedestrian injuries would be observed in areas with higher unemployment, lesser income, greater population, and a predominance of younger or older age populations. Archival and individual-level data from a general population telephone survey were obtained from four California communities. The survey data included sociodemographic and drinking pattern measures. Archival data included environmental measures relevant to pedestrian travel and measures of alcohol availability. Units of analysis were geographic areas within each community defined by the spatial clustering of telephone survey respondents. The results showed that alcohol-involved pedestrian collisions occurred more often in areas with greater bar densities and greater population, and where the local population reported drinking more alcohol per drinking occasion. Pedestrian collisions not involving alcohol occurred more often in lower income areas with greater population and cross-street densities, and in areas having either younger or older age populations. The identification of neighborhood variables associated with pedestrian collisions has important implications for policy formation and targeted prevention efforts.

An ecological study of the locations of schools and child pedestrian injury collisions

Geographic studies of the incidence and prevalence of child pedestrian injury collisions in different community environments have been primarily descriptive and idiosyncratic, reflecting one or another likely determinant of the places where these injuries occur. The current study maintains that multiple determinants of child pedestrian injury collisions must be considered in evaluating the unique contributions of any one community feature to injury rates. These features include local characteristics of populations, such as rates of unemployment, and places, such as locations of schools. Schools are one stable geographic feature associated with regular, often concentrated periods of complex and congested traffic patterns. The objective of the present study was to examine annual rates of child pedestrian injury in four California communities with a focus on the unique contribution of schools to injury risk. We predicted that annual numbers of child pedestrian injury collisions (both in-school and summer combined) would be greater in communities with higher youth population densities, more unemployment, fewer high-income households, and higher traffic flow. It was hypothesized that youth population density and its interaction with the number of schools in a given area would be related to greater rates of child pedestrian collisions during in-school months. An ecological approach was taken that divided the four communities into 102 geographic units with an average of 6321 people residing in each unit. Archival data on traffic flow, number of child pedestrian injury collisions and locations of schools were obtained from state agencies. Individual-level data were obtained from a general population survey conducted in the communities. The results showed that annual numbers of injuries were greater in areas with higher youth population densities, more unemployment, fewer high-income households, and greater traffic flow. Annual numbers of injuries during in-school months were greater in areas containing middle schools and greater population densities of youth.

Race and Sex Differences in Head Size and IQ

Abstract An analysis of IQ in relation to head size (and by inference, brain size) was performed on some 14,000 children and their full siblings, almost evenly divided by race (white and black) and sex, on whom data were obtained at ages 4 and 7 years in the National Collaborative Perinatal Project. Within each race × sex group, IQ is significantly correlated with head size, age and body size having been partialed out. A significant positive correlation between IQ × head size exists not only within subjects (at ages 4 and 7) but also within families and between families (at age 7 only). The within-families correlation (at age 7) is consistent with an intrinsic or pleiotropic correlation between the mental and physical variables. No significant positive correlation within families appeared at age 4, despite a significant within-subjects correlation at that age. As yet, there are only speculative explanations of the disparity between the age 4 and 7 within-family correlations of head size with IQ. Although general body size is also correlated with IQ within subjects and between families, the correlation does not exist within families in either age group, which rules out a pleiotropic correlation between body size and IQ. There are both race and sex differences in head size, although the sex difference in IQ is nil. White and black children who are matched on IQ show, on average, virtually zero difference in head size.

An Exploratory Study Examining the Spatial Dynamics of Illicit Drug Availability and Rates of Drug Use.

This study examines the spatial relationship between drug availability and rates of drug use in neighborhood areas. Responses from 16,083 individuals were analyzed at the zip code level (n = 158) and analyses were conducted separately for youth and adults using spatial regression techniques. The dependent variable is the percentage of respondents using drugs in the past year. Neighborhood drug availability (the major independent variable) was measured by the percentage of non-drug users who had been approached to purchase drugs. Data were obtained as part of the Fighting Back community evaluation. For youth (aged 12 to 18), drug sales in adjacent and surrounding areas were positively associated with self-reported drug use in areas where youth were residents. For adults, drug sales within the neighborhood were negatively associated with drug use, while drug sales in immediately adjacent neighborhoods were positively related to self-reports of drug use. Findings suggest that the areas where rates of drug users are greatest are not necessarily the same area where drugs are sold. Designing strategies to reduce the supply of drugs should receive input from city and regional planners and developers, as well as law enforcement and public health professionals.

Suicide and Alcohol: Do Outlets Play a Role?

BACKGROUND The purpose of this study was to determine whether the number of alcohol outlets in local and adjacent areas, in particular bars, was related over time to completed suicide and suicide attempts. There is evidence both from studies of individuals and time series aggregate studies, mostly at the national level, of substantial alcohol involvement in suicide, but no small-area, longitudinal studies have been carried out. The present study is the first that is both longitudinal and based on a large number of small spatial units, California zip codes, a level of resolution permitting analysis of the relationship between local alcohol access and suicide rates over time. METHOD Longitudinal data were obtained from 581 consistently defined zip code areas over 6 years (1995-2000) using data from the California Index Locations Database, a geographic information system that contains both population and place information with spatial attributes for the entire state. Measures obtained from each zip code included population characteristics (e.g., median age) and place characteristics (e.g., numbers of retail and alcohol outlets) which were related in separate analyses to (i) suicide mortality and (ii) the number of hospitalizations for injuries caused by suicide attempts. The effect of place characteristics in zip code areas adjacent to each of the 581 local zip codes (spatial lags) was also assessed. Analysis methods were random effects models corrected for spatial autocorrelation. RESULTS Completed suicide rates were higher in zip code areas with greater local and lagged bar densities; and higher in areas with greater local but not lagged off-premise outlet densities. Whereas completed suicide rates were lower among blacks and Hispanics, completed suicide rates were higher among low income, older whites living in less densely populated areas, that is, rural areas. Rates of suicide attempts were higher in zip code areas with greater local but not lagged bar densities, and higher among low income younger whites living in smaller households and in rural areas. Rates of attempted suicide were also higher among blacks. Completed suicide and suicide attempt rates were lower in zip code areas with greater local restaurant densities; there were no lagged effects for restaurants. CONCLUSIONS Bar densities in particular appear related to suicide, meaning, because this is an aggregate-level spatial analysis, that suicides, both attempted and completed, occur at greater rates in rural community areas with greater bar densities. Because the suicide rate is highest in rural areas, this study suggests that although the number of completed and attempted suicides is no doubt greater in absolute numbers in urban areas, the suicide rate, both completed and attempted, is greater in rural areas, which draws attention, perhaps much needed, to the problems of rural America.

Assessing Correlates of the Growth and Extent of Methamphetamine Abuse and Dependence in California

Using aggregate-level data, this study performed cross-sectional analyses on all 1,628 populated California zip code areas and longitudinal analyses on 581 consistently defined zip codes over six years (1995–2000), relating place and population characteristics of these areas to rates of hospital discharges for amphetamine dependence/abuse using linear spatial models. Analyzing the data in two ways, spatial time series cross-sections and spatial difference models, amphetamine dependence/abuse were greatest in rural areas with more young low-income whites, larger numbers of retail and alcohol outlets, and smaller numbers of restaurants. Growth rates of these problems were greater in areas with higher income and larger non-White and Hispanic populations. This suggests that there was some change in the penetration of the methamphetamine epidemic into different population groups during this time. Study implications and limitations are discussed.