Lorna H. McNeill

The landscape of recombination in African Americans

Recombination, together with mutation, gives rise to genetic variation in populations. Here we leverage the recent mixture of people of African and European ancestry in the Americas to build a genetic map measuring the probability of crossing over at each position in the genome, based on about 2.1 million crossovers in 30,000 unrelated African Americans. At intervals of more than three megabases it is nearly identical to a map built in Europeans. At finer scales it differs significantly, and we identify about 2,500 recombination hotspots that are active in people of West African ancestry but nearly inactive in Europeans. The probability of a crossover at these hotspots is almost fully controlled by the alleles an individual carries at PRDM9 (P value < 10−245). We identify a 17-base-pair DNA sequence motif that is enriched in these hotspots, and is an excellent match to the predicted binding target of PRDM9 alleles common in West Africans and rare in Europeans. Sites of this motif are predicted to be risk loci for disease-causing genomic rearrangements in individuals carrying these alleles. More generally, this map provides a resource for research in human genetic variation and evolution.

Safe To Walk? Neighborhood Safety and Physical Activity Among Public Housing Residents

Background Despite its health benefits, physical inactivity is pervasive, particularly among those living in lower-income urban communities. In such settings, neighborhood safety may impact willingness to be regularly physically active. We examined the association of perceived neighborhood safety with pedometer-determined physical activity and physical activity self-efficacy. Methods and Findings Participants were 1,180 predominantly racial/ethnic minority adults recruited from 12 urban low-income housing complexes in metropolitan Boston. Participants completed a 5-d pedometer data-collection protocol and self-reported their perceptions of neighborhood safety and self-efficacy (i.e., confidence in the ability to be physically active). Gender-stratified bivariate and multivariable random effects models were estimated to account for within-site clustering. Most participants reported feeling safe during the day, while just over one-third (36%) felt safe at night. We found no association between daytime safety reports and physical activity among both men and women. There was also no association between night-time safety reports and physical activity among men (p = 0.23) but women who reported feeling unsafe (versus safe) at night showed significantly fewer steps per day (4,302 versus 5,178, p = 0.01). Perceiving ones neighborhood as unsafe during the day was associated with significantly lower odds of having high physical activity self-efficacy among both men (OR 0.40, p = 0.01) and women (OR 0.68, p = 0.02). Conclusions Residing in a neighborhood that is perceived to be unsafe at night is a barrier to regular physical activity among individuals, especially women, living in urban low-income housing. Feeling unsafe may also diminish confidence in the ability to be more physically active. Both of these factors may limit the effectiveness of physical activity promotion strategies delivered in similar settings.

The Association Between Social Factors and Physical Activity Among Low-Income Adults Living in Public Housing

OBJECTIVES We sought to examine the association between structural, functional, and normative social factors and physical activity among urban, low-income, racially/ethnically diverse adults. METHODS We conducted a baseline cross-sectional survey among residents of 12 low-income housing communities in metropolitan Boston, Massachusetts. Participants were also asked to wear a pedometer for 5 days. We analyzed complete data from 1112 residents (weighted n = 1635). RESULTS Residents with smaller social networks were significantly less physically active than were residents with larger social networks (b = -1503.7; P = .01) and residents with conflicting demands were more active than were residents with none (b = 601.6; P = .01), when we controlled for employment status, gender, poverty level, current health status, age, and perceived safety. Social networks were most strongly associated with physical activity among Hispanics and younger residents (aged 18-35 years). CONCLUSIONS These findings indicate that social factors, including social networks and role-related conflicting demands, may be important drivers of physical activity among low-income populations. Researchers and practitioners should consider social factors in developing multilevel physical activity interventions for this population.

Density and proximity of fast food restaurants and body mass index among African Americans.

OBJECTIVES The purpose of this study was to address current gaps in the literature by examining the associations of fast food restaurant (FFR) density around the home and FFR proximity to the home, respectively, with body mass index (BMI) among a large sample of African American adults from Houston, Texas. METHODS We used generalized linear models with generalized estimating equations to examine associations of FFR density at 0.5-, 1-, 2-, and 5-mile road network buffers around the home with BMI and associations of the closest FFR to the home with BMI. All models were adjusted for a range of individual-level covariates and neighborhood socioeconomic status. We additionally investigated the moderating effects of household income on these relations. Data were collected from December 2008 to July 2009. RESULTS FFR density was not associated with BMI in the main analyses. However, FFR density at 0.5, 1, and 2 miles was positively associated with BMI among participants with lower incomes (P ≤ .025). Closer FFR proximity was associated with higher BMI among all participants (P < .001), with stronger associations emerging among those of lower income (P < .013) relative to higher income (P < .014). CONCLUSIONS Additional research with more diverse African American samples is needed, but results supported the potential for the fast food environment to affect BMI among African Americans, particularly among those of lower economic means.

Genome-wide Scan of 29,141 African Americans Finds No Evidence of Directional Selection since Admixture

The extent of recent selection in admixed populations is currently an unresolved question. We scanned the genomes of 29,141 African Americans and failed to find any genome-wide-significant deviations in local ancestry, indicating no evidence of selection influencing ancestry after admixture. A recent analysis of data from 1,890 African Americans reported that there was evidence of selection in African Americans after their ancestors left Africa, both before and after admixture. Selection after admixture was reported on the basis of deviations in local ancestry, and selection before admixture was reported on the basis of allele-frequency differences between African Americans and African populations. The local-ancestry deviations reported by the previous study did not replicate in our very large sample, and we show that such deviations were expected purely by chance, given the number of hypotheses tested. We further show that the previous studys conclusion of selection in African Americans before admixture is also subject to doubt. This is because the FST statistics they used were inflated and because true signals of unusual allele-frequency differences between African Americans and African populations would be best explained by selection that occurred in Africa prior to migration to the Americas.

Associations of perceived neighborhood physical and social environments with physical activity and television viewing in African-American men and women.

Purpose. Few studies have assessed how attributes of neighborhood environments contribute to sedentary, in addition to active, behaviors. This study investigated associations of perceived social and physical aspects of neighborhood environments with television (TV) viewing and physical activity (PA) in African-American adults. Design. Cross-sectional analysis of self-reported survey. Setting. Large mega-church in Houston, Texas. Subjects. A total of 1374 African-American men and women. Measures. Outcomes included log-transformed daily TV viewing and participation in medium/high levels of PA, measured by the short version of the International Physical Activity Questionnaire. Neighborhood perceptions were assessed with the Social Cohesion and Trust and the Neighborhood Problems scales. Analysis. Multivariable models that controlled for clustering within neighborhoods. Results. Reporting more neighborhood problems was significantly associated with greater log-transformed TV viewing in women (β = .017, SE = .006, p = .003), and social cohesion was positively associated with PA in women (odds ratio = 1.06, 95% confidence interval = 1.02, 1.11, p = .006). Concerns about litter and walking after dark and a lack of places to shop were associated with increased TV viewing among women, and concerns about traffic and walking after dark were associated with reduced PA among men. Conclusion. Physical and social neighborhood conditions were associated with TV viewing and PA, particularly in women. Neighborhood-based strategies to reduce sedentary behaviors and enhance PA should include attention to social as well as physical aspects of neighborhood environments.

Individual, social and environmental correlates of physical activity in overweight and obese African American and Hispanic women: A structural equation model analysis

Objective Ecologic frameworks account for multilevel factors related to physical activity (PA) and may be used to develop effective interventions for women. The purpose of this study was to examine the influence of individual, social and environmental factors on PA among African American and Hispanic women using structural equation modeling. Methods Overweight and obese women (N = 164, 65.9% African American) completed a 7-day accelerometer protocol, a physical assessment, and questionnaires on body image, self-efficacy, motivational readiness, social support, home environment for physical activity and perceived environment. Trained assessors evaluated each participants neighborhood and collected objective measures of physical activity resources and the pedestrian environment. Assessments were completed between 2006 and 2008. Results Structural model fit was acceptable (RMSEA = .030). Body composition and image was negatively associated with PA, and motivational readiness had an indirect effect on PA through body composition and image. PA resources and the pedestrian environment operated through the perceived environment to positively influence neighborhood cohesion, which was positively associated with body composition and image. Conclusion PA is more heavily influenced by intrapersonal factors related to weight. Improving intrapersonal factors related to weight and perceptions of the environment may lead to increased PA in African American and Hispanic women.

Health literacy, smoking, and health indicators in African American adults

We examined cross-sectional associations of health literacy (HL) with smoking and other established health indicators among 1,467 African American adults. Data emanated from a longitudinal cohort study designed to investigate cancer risk factors among church-going African American adults. We conducted linear and logistic regression analyses to assess associations between HL and health indicators. HL was assessed using an established single-item screening question. Outcomes included indicators of poor physical health (cigarette smoking, self-rated general and physical health) and mental health (self-rated mental health, depressive symptoms, perceived stress). Nearly 19% of participants had low HL. Low HL was significantly associated with current smoking, poorer self-rated general and physical health, and higher perceived stress (ps < .05) even after we controlled for demographic variables (i.e., age, gender, relationship status) and indicators of socioeconomic status (i.e., education, income, insurance status). Low HL appears to be an independent risk factor for smoking and other indicators of poor physical and mental health in a large sample of African American adults. Future directions and clinical implications are discussed.

Subjective social status and health behaviors among African Americans.

OBJECTIVES To examine associations of the US and community subjective social status (SSS) ladders with smoking status, at-risk drinking, fruit and vegetable intake, physical activity, and body mass index among 1467 church-going African American adults from a larger cohort study. METHODS Regression analyses, adjusted for sociodemographics, examined associations between SSS ladders and health behaviors. RESULTS The SSS-US ladder was significantly associated with fruit and vegetable consumption (p = .007) and physical activity (p = .005). The SSS-community ladder was not significantly associated with any health behaviors. CONCLUSIONS Among this sample of African Americans, the SSS-US ladder is more predictive of some health behaviors than is the SSS-community ladder.

SALSA: SAving lives staying active to promote physical activity and healthy eating

Physical inactivity, poor dietary habits, and obesity are vexing problems among minorities. SAving Lives, Staying Active (SALSA) was an 8-week randomized controlled crossover design, pilot study to promote regular physical activity (PA) and fruit and vegetable (FV) consumption as a means to preventing weight gain among women of color. Participants completed measures of demographics, PA, and dietary habits. Women (N = 50; M = 42 years) who participated were overweight (MBMI = 29.7 kg/m2; Mbody fat = 38.5%) and reported low levels of leisure time PA (M = 10.7 MET-min/wk) and FV consumption (M = 4.2 servings/day). All were randomized to a four-week (1) semiweekly Latin dance group or (2) internet-based dietary education group. All participants reported a significant increase in weekly leisure time PA from baseline (M = 10.7 MET-min/wk) to follow up (M = 34.0 MET-min/wk, P < .001), and FV consumption increased over time by group (P = .02). Data suggest that Latin dance interventions to improve PA and web-based interventions to improve dietary habits show promise for improving health among women of color.