Adapting the Index of Relative Rurality (IRR) to Estimate Rurality at the ZIP Code Level: A Rural Classification System in Health Services Research

BACKGROUND

Accurate analysis of health problems facing rural residents depends on how rurality is defined. Health services research relies frequently on the rural urban commuting area (RUCA) codes to estimate rurality at the small area level. We modified the county-level Index of Relative Rurality (IRR) to the ZIP code level (IRRZIP ) to create an alternative small-area-level rural classification system. We then compared how the 2 rural classification systems differ in how rural areas and populations are defined and in methodological analysis.

METHODS

We linked data for veterans (n = 37,466) who attended the VA Pittsburgh Healthcare System to 2000 United States Census and the US Department of Agriculture's Economic Research Service data.

RESULTS

The RUCA and the IRRZIP do not consistently classify the same ZIP code areas and populations as rural. Using the IRRZIP , each 10th increment in increased rurality was associated with a 2.6 increased odds of receiving primary care at a satellite clinic.

CONCLUSIONS

The IRRZIP is a straightforward measure that is easy to use and interpret and may be a relevant alternative rural classification system that can be used in health services research.

Non-residential neighborhood exposures suppress neighborhood effects on self-rated health

In prior research, neighborhood effects have often been weak or inconsistent in predicting specific causes of mortality and morbidity. To determine whether residential neighborhood effects are suppressed by exposure to other environments, we examined the effect on adult self-rated health of non-residential environments that figure in individuals' daily routines. We linked the 2000 US Census data with the Los Angeles Family and Neighborhood Study (L.A.FANS) database, which consists of 3323 adults sampled from neighborhoods in LA County. Characteristics of census tracts where respondents lived, worked, shopped, sought medical care, worshipped and spent "other" time were obtained from the 2000 US Census. Weighted multilevel linear and clustered generalized ordered logistic regressions were used to estimate associations between self-rated health and non-residential neighborhood exposures after adjustment for individual-level factors and exposure to residential neighborhoods. We found that residence in disadvantaged neighborhoods was associated with worse self-rated health. In a dose-response fashion, the greater the exposure to less disadvantaged non-residential neighborhoods in the course of routine activities, the greater the magnitude in improved self-rated health. Models including non-residential neighborhood exposure increase the magnitude and significance of the association between residential neighborhoods and health. In conclusion, individuals' exposure to non-residential neighborhoods confounds and suppresses the association of residential neighborhoods with health and could explain why previous studies may not have found robust associations between residential neighborhood predictors and health.

The built environment and collective efficacy

Collective efficacy, i.e., perception of mutual trust and willingness to help each other, is a measure of neighborhood social capital and has been associated with positive health outcomes including lower rates of assaults, homicide, premature mortality, and asthma. Collective efficacy is frequently considered a "cause", but we hypothesized that environmental features might be the foundation for or the etiology of personal reports of neighborhood collective efficacy. We analyzed data from the Los Angeles Family and Neighborhood Study (LAFANS) together with geographical data from Los Angeles County to determine which social and environmental features were associated with personal reports of collective efficacy, including presence of parks, alcohol outlets, elementary schools and fast food outlets. We used multi-level modeling controlling for age, education, annual family income, sex, marital status, employment and race/ethnicity at the individual level. At the tract level, we controlled for tract-level disadvantage, the number of off-sale alcohol outlets per roadway mile, the number of parks and the number of fast food outlets within the tract and within 1/2 mile of the tract's boundaries. We found that parks were independently and positively associated with collective efficacy; alcohol outlets were negatively associated with collective efficacy only when tract-level disadvantage was not included in the model. Fast food outlets and elementary schools were not linearly related to collective efficacy. Certain environmental features may set the stage for neighborhood social interactions, thus serving as a foundation for underlying health and well-being. Altering these environmental features may have greater than expected impact on health.

You are where you shop: grocery store locations, weight, and neighborhoods

BACKGROUND

Residents in poor neighborhoods have higher body mass index (BMI) and eat less healthfully. One possible reason might be the quality of available foods in their area. Location of grocery stores where individuals shop and its association with BMI were examined.

METHODS

The 2000 U.S. Census data were linked with the Los Angeles Family and Neighborhood Study (L.A.FANS) database, which consists of 2620 adults sampled from 65 neighborhoods in Los Angeles County between 2000 and 2002. In 2005, multilevel linear regressions were used to estimate the associations between BMI and socioeconomic characteristics of grocery store locations after adjustment for individual-level factors and socioeconomic characteristics of residential neighborhoods.

RESULTS

Individuals have higher BMI if they reside in disadvantaged areas and in areas where the average person frequents grocery stores located in more disadvantaged neighborhoods. Those who own cars and travel farther to their grocery stores also have higher BMI. When controlling for grocery store census tract socioeconomic status (SES), the association between residential census tract SES and BMI becomes stronger.

CONCLUSIONS

Where people shop for groceries and distance traveled to grocery stores are independently associated with BMI. Exposure to grocery store mediates and suppresses the association of residential neighborhoods with BMI and could explain why previous studies may not have found robust associations between residential neighborhood predictors and BMI.

Residential segregation and Latino, black and white mortality in New York City

Although racial segregation is associated with health status, few studies have examined this relationship among Latinos. We examined the effect of race/ethnic group concentration of Latinos, blacks and whites on all-cause mortality rates within a highly segregated metropolitan area, New York City (NYC). We linked NYC mortality records from 1999 and 2000 with the 2000 U.S. Census data by zip code area. Age-adjusted mortality rates by race/ethnic concentration were calculated. Linear regression was used to determine the association between population characteristics and mortality. Blacks living in predominantly black areas had lower all-cause mortality rates than blacks living in other areas regardless of gender (1616/100,000 vs. 2014/100,000 for men; 1032/100,000 vs. 1362/100,000 for women). Amongst whites, those living in predominantly white areas had the lowest mortality rates. Latinos living in predominantly Latino areas had lower mortality rates than those in predominantly black areas (1187/100,000 vs.1950/100,000 for men; 760/100,000 vs. 779/100,000 for women). After adjustment for socioeconomic conditions, whites, older blacks, and young Latino men experienced decreasing mortality rates when living in areas with increasing similar race/ethnic concentrations. Increasing residential concentration of blacks is independently associated with lower mortality in older blacks; similarly, increasing residential concentration of Latinos and whites is associated with lower mortality in young Latino men and whites, respectively.

Purification and partial characterization of cellular retinol-binding protein, type two, from human small intestine

Two forms of human cellular retinol-binding protein, type II [hCRBP(II)A and hCRBP(II)B], were purified from the small intestine in a three-step purification procedure. The N-terminal sequence of CRBP(II)A was determined to 36 residues and found to have only a single residue difference when compared with the N-terminal sequence in rat; the amino acid change maintained charge. hCRBP(II)B was blocked at the N-terminus, presumably because of N-acetylation of the initial threonine residue as previously established for CRBP(II)B from rat. This blockage did not affect the binding properties of the protein. The ability of pure hCRBP(II) to bind all-trans-retinol, retinal and retinoic acid was examined by competitive binding assay and compared with the binding specificity of pure human cellular retinol-binding protein (hCRBP). Retinoic acid did not compete with retinol for binding to either protein. Retinal competed with retinol for binding to hCRBP(II) but not to hCRBP, consistent with what was observed for the homologous proteins of rats. Polyclonal antiserum against hCRBP(II)B was produced that recognized both forms of hCRBP(II) in Western blotting and RIA but did not react with hCRBP. Distribution of hCRBP(II) was determined in the jejunum. Higher concentrations of hCRBP(II) were observed in the proximal portion compared with the distal portion. Although concentrations varied in individual intestinal samples, concentrations up to 1% of total mucosal protein were observed in some samples. These results provide tools for further investigation of the role of hCRBP(II) and suggest that previous results from rats, in this important aspect, are relevant to human metabolism of vitamin A.

DNA denatures upon drying after ethanol precipitation

We have observed that ethanol precipitation and subsequent drying of small (less than 400 bp) radiolabelled DNA fragments is able to induce a transition to a form that migrates aberrantly on acrylamide gels. This unusual form has increased sensitivity to S1 nuclease, decreased sensitivity to restriction enzymes, and a concentration dependence for the reversion to the duplex form. Apparently, DNA denatures upon dehydration so that redissolving at low dilution will allow the collapse of DNA fragments into single-stranded hairpin structures. These structures are stable enough at low dilution to prevent complete reannealing of single stranded species. These single stranded species show strong binding to unidentified proteins present in nuclear extracts. This may give rise to misleading interpretations of mobility shift assays, especially if the single-stranded conformers have a similar mobility to the duplex fragment, which can occur in fragments that are 50-100 bp long. Evidence is presented that DNA, in general, denatures upon dehydration, but that hindrances to rotation in the solid state may prevent long fragments from dissociating.