Preference for immediate reinforcement over delayed reinforcement: relation between delay discounting and health behavior

Reinforcement from engaging in health behaviors is often delayed by several months or years, a circumstance partly responsible for some people’s increased preference for engaging in unhealthy behaviors associated with immediate reinforcement. To examine whether individuals who discount the future engage in fewer health behaviors, 72 young adults completed questionnaires assessing health behaviors and impulsiveness and laboratory-behavioral measures of impulsive decision making. Regression analyses of impulsivity measures predicting health behavior were only significant for one measure, the Experiential Discounting Task, a task in which monetary consequences of choice were actually experienced by study participants. Participants who discounted most by delay (i.e., exhibited impulsive choice) engaged in fewer health behaviors than those who showed less impulsive responding. This task, in contrast to a hypothetical choice task or self-reported impulsiveness, measures the actual behavior of discounting by delay, and was the facet of impulsive decision making most closely associated with adopting a range of health behaviors.     

Human Leukocyte Antigens and Cellular Immune Responses to Anthrax Vaccine Adsorbed

Interindividual variations in vaccine-induced immune responses are in part due to host genetic polymorphisms in the human leukocyte antigen (HLA) and other gene families. This study examined associations between HLA genotypes, haplotypes, and homozygosity and protective antigen (PA)-specific cellular immune responses in healthy subjects following immunization with Anthrax Vaccine Adsorbed (AVA). While limited associations were observed between individual HLA alleles or haplotypes and variable lymphocyte proliferative (LP) responses to AVA, analyses of homozygosity supported the hypothesis of a “heterozygote advantage.” Individuals who were homozygous for any HLA locus demonstrated significantly lower PA-specific LP than subjects who were heterozygous at all eight loci (median stimulation indices [SI], 1.84 versus 2.95, P = 0.009). Similarly, we found that class I (HLA-A) and class II (HLA-DQA1 and HLA-DQB1) homozygosity was significantly associated with an overall decrease in LP compared with heterozygosity at those three loci. Specifically, individuals who were homozygous at these loci had significantly lower PA-specific LP than subjects heterozygous for HLA-A (median SI, 1.48 versus 2.13, P = 0.005), HLA-DQA1 (median SI, 1.75 versus 2.11, P = 0.007), and HLA-DQB1 (median SI, 1.48 versus 2.13, P = 0.002) loci, respectively. Finally, homozygosity at an increasing number (≥4) of HLA loci was significantly correlated with a reduction in LP response (P < 0.001) in a dose-dependent manner. Additional studies are needed to reproduce these findings and determine whether HLA-heterozygous individuals generate stronger cellular immune response to other virulence factors (Bacillus anthracis LF and EF) than HLA-homozygous subjects.     

Examining Relations Between Obsessive-Compulsive Features,Substance-Use Disorders,and Antisocial Personality Disorder in the Vietnam Era Twin Cohort

Classes of obsessive-compulsive features differing both quantitatively and qualitatively have been linked to gambling disorder. This secondary data analysis sought to extend this line of investigation to examine the extent to which previously reported latent obsessive-compulsive classes may relate to externalizing conditions in a sample of 1675 twin male veterans recruited and surveyed for studies of gambling behaviors/disorder. Using latent class analysis and multivariate regression, we found that participants who reported the highest levels of obsessive-compulsive features were more likely to meet criteria for cannabis abuse and dependence and antisocial personality disorder. When adjusting for co-occurring disorders, the relationship with antisocial personality disorder remained significant whereas those for cannabis use disorders did not. These results highlight the potential utility of considering obsessive-compulsive features within a transdiagnostic framework and suggest that specific externalizing disorders have important links to obsessive-compulsive features. Future research is needed to extend these findings to other samples.

     

A study of interobserver reproducibility of morphologic lesions of focal segmental glomerulosclerosis

The morphology of focal segmental glomerulosclerosis (FSGS) includes collapsing, cellular, and sclerosing forms. The Columbia Working Classification of FSGS divides these into collapsing (COLL), cellular (CELL), tip lesion (TIP), perihilar (PH), and not otherwise specified (NOS) morphologic forms. This study examined the ability of renal pathologists to classify FSGS using single light microscopic images of glomeruli as a uniform data set. Sixty-one digital images of individual glomeruli with FSGS, stained by periodic acid-Schiff or Jones methenamine silver methods, were classified independently by six specialist renal pathologists. Diagnostic consistency was quantified using the kappa statistic for nominal categories. Agreement for 366 diagnoses by six observers was 75.2 % with a kappa value of 0.676. Six of six observers agreed in 31 of 61 cases (50.8 %) and four or more in 53 cases (86.9 %). Respective kappa values ranged from moderate to good: COLL 0.77, CELL 0.53, TIP 0.76, PH 0.84, and NOS 0.60. Capillary retraction with lobular expansion, hypercellularity, and sclerosis in the same glomerular segments, and the location of segmental lesions were sources of diagnostic inconsistency. The morphologic forms of FSGS defined by the Columbia system are reproducible between observers and have a low probability of confusion between forms. Individual glomeruli may have overlapping features of more than one form of FSGS.     

Collecting Maternal Health Information From HIV-Positive Pregnant Women Using Mobile Phone-Assisted Face-to-Face Interviews in Southern Africa

Background

Most of the world’s women living with human immunodeficiency virus (HIV) reside in sub-Saharan Africa. Although efforts to reduce mother-to-child transmission are underway, obtaining complete and accurate data from rural clinical sites to track progress presents a major challenge.

Objective

To describe the acceptability and feasibility of mobile phones as a tool for clinic-based face-to-face data collection with pregnant women living with HIV in South Africa.

Methods

As part of a larger clinic-based trial, 16 interviewers were trained to conduct mobile phone–assisted personal interviews (MPAPI). These interviewers (participant group 1) completed the same short questionnaire based on items from the Technology Acceptance Model at 3 different time points. Questions were asked before training, after training, and 3 months after deployment to clinic facilities. In addition, before the start of the primary intervention trial in which this substudy was undertaken, 12 mothers living with HIV (MLH) took part in a focus group discussion exploring the acceptability of MPAPI (participant group 2). Finally, a sample of MLH (n=512) enrolled in the primary trial were asked to assess their experience of being interviewed by MPAPI (participant group 3).

Results

Acceptability of the method was found to be high among the 16 interviewers in group 1. Perceived usefulness was reported to be slightly higher than perceived ease of use across the 3 time points. After 3 months of field use, interviewer perceptions of both perceived ease of use and perceived usefulness were found to be higher than before training. The feasibility of conducting MPAPI interviews in this setting was found to be high. Network coverage was available in all clinics and hardware, software, cost, and secure transmission to the data center presented no significant challenges over the 21-month period. For the 12 MHL participants in group 2, anxiety about the multimedia capabilities of the phone was evident. Their concern centered on the possibility that their privacy may be invaded by interviewers using the mobile phone camera to photograph them. For participants in group 3, having the interviewer sit beside vs across from the interviewee during the MPAPI interview was received positively by 94.7% of MHL. Privacy (6.3%) and confidentiality (5.3%) concerns were low for group 3 MHL.

Conclusions

Mobile phones were found both to be acceptable and feasible in the collection of maternal and child health data from women living with HIV in South Africa.

Trial Registration

Clinicaltrials.gov {"type":"clinical-trial","attrs":{"text":"NCT00972699","term_id":"NCT00972699"}}NCT00972699; http://clinicaltrials.gov/ct2/show/{"type":"clinical-trial","attrs":{"text":"NCT00972699","term_id":"NCT00972699"}}NCT00972699 (Archived by WebCite at http://clinicaltrials.gov/ct2/show/{"type":"clinical-trial","attrs":{"text":"NCT00972699","term_id":"NCT00972699"}}NCT00972699)     

Supervised Patient Self-Testing of Warfarin Therapy Using an Online System

Background

Point-of-care international normalized ratio (INR) monitoring devices simplify warfarin management by allowing selected patients to monitor their own therapy in their homes. Patient self-testing (PST) has been shown to improve the clinical outcomes of warfarin therapy compared to usual care.

Objective

To compare management of warfarin therapy using PST combined with online supervision by physicians via a custom system with usual warfarin management, which involved laboratory testing and physician dosing.

Methods

Interested patients were recruited via community pharmacies to participate in a warfarin PST training program. Participants were required to have a long-term indication for warfarin, have been taking warfarin for at least 6 months, and have Internet access in their home. The training involved two sessions covering theoretical aspects of warfarin therapy, use of the CoaguChek XS, and the study website. Following training, patients monitored their INR once weekly for up to 3 months. Patients and physicians utilized a secure website to communicate INR values, dosage recommendations, and clinical incidents. Physicians provided a 6-12 month history of INR results for comparison with study results. The percentage of time spent within the therapeutic INR range (TTR) was the primary outcome, with participants acting as their own historical controls. The percentage of INR tests in range and participant satisfaction were secondary outcomes.

Results

Sixteen patients completed training requirements. The mean age of participants was 69.8 (SD 10.1) years. TTR improved significantly from 66.4% to 78.4% during PST (P=.01), and the number of tests within the target range also improved significantly (from 66.0% at prior to the study to 75.9% during PST; P=.04). Patients and physicians expressed a high degree of satisfaction with the monitoring strategy and online system.

Conclusions

PST supported by an online system for supervision was associated with improved INR control compared to usual care in a small group of elderly patients. Further research is warranted to investigate the clinical outcomes and cost-effectiveness of online systems to support patients monitoring medications and chronic conditions in the home.     

Drug driving among injecting drug users in Sydney, Australia: prevalence, risk factors and risk perceptions

Aims To examine the prevalence of drug driving, the prevalence of drug‐related motor vehicle accidents, risk perceptions of drug driving and factors associated with drug driving among injecting drug users (IDU). Design Cross‐sectional survey. Setting Sydney, Australia. Participants Three hundred current IDU. Findings Ninety‐five per cent had driven a vehicle, 74% in the previous 12 months (‘current drivers’). Eighty‐seven per cent of life‐time drivers reported having drug driven, and 88% of current drivers had drug driven in the previous 12 months. There were no significant sex differences in life‐time or recent drug driving. The most common drugs used before driving in the preceding year were: cannabis, heroin, amphetamines and cocaine. A third of life‐time drivers reported having had a drug driving accident, with males more likely to have done so, and 9% of current drivers reported a drug driving accident in the previous year. The most common drugs that had been used before the most recent drug driving accident were heroin, cannabis and alcohol. Alcohol was perceived to be the most dangerous substance for driving performance and cannabis the least dangerous. Recent drug drivers perceived drug driving to be less dangerous than non‐drug drivers. Recent drug drivers had driven more frequently over the preceding 12 months, had significantly higher levels of dependence, higher frequency of drug use, more extensive polydrug use and were more likely to have used and/or injected a drug in a car in the previous 12 months. Conclusions Drug driving and drug‐related accidents are large‐scale public health problems among IDU. These behaviours pose serious risks to IDU themselves and to the broader community.     

From the Cover: Contrasting drivers of diversity in hosts and parasites across the tropical Andes

Geographic turnover in community composition is created and maintained by eco-evolutionary forces that limit the ranges of species. One such force may be antagonistic interactions among hosts and parasites, but its general importance is unknown. Understanding the processes that underpin turnover requires distinguishing the contributions of key abiotic and biotic drivers over a range of spatial and temporal scales. Here, we address these challenges using flexible, nonlinear models to identify the factors that underlie richness (alpha diversity) and turnover (beta diversity) patterns of interacting host and parasite communities in a global biodiversity hot spot. We sampled 18 communities in the Peruvian Andes, encompassing ∼1,350 bird species and ∼400 hemosporidian parasite lineages, and spanning broad ranges of elevation, climate, primary productivity, and species richness. Turnover in both parasite and host communities was most strongly predicted by variation in precipitation, but secondary predictors differed between parasites and hosts, and between contemporary and phylogenetic timescales. Host communities shaped parasite diversity patterns, but there was little evidence for reciprocal effects. The results for parasite communities contradicted the prevailing view that biotic interactions filter communities at local scales while environmental filtering and dispersal barriers shape regional communities. Rather, subtle differences in precipitation had strong, fine-scale effects on parasite turnover while host–community effects only manifested at broad scales. We used these models to map bird and parasite turnover onto the ecological gradients of the Andean landscape, illustrating beta-diversity hot spots and their mechanistic underpinnings.

Turnover in community composition across space, or “beta diversity,” reflects eco-evolutionary processes that determine range limits of species (1–3). These processes include adaptive specialization on particular habitats, barriers to dispersal, and interactions among species (4–6). Antagonistic interactions between hosts and parasites may have an underappreciated effect on turnover (7), as evidenced by the sensitivity of host populations to novel parasites. For example, introductions of avian malaria (Plasmodium relictum) and avian pox (Avipoxvirus) led to extinctions or range contractions for dozens of endemic Hawaiian honeycreeper species (8). Introduced parasites have also driven shifts in community composition when competing hosts differ in susceptibility to infection (9). While these cases highlight extreme impacts of parasites on host communities, it remains unclear whether host–parasite interactions generally drive turnover in continental faunas, whether such effects are reciprocal or unidirectional, and whether these interactions also impact diversity patterns at regional scales or over evolutionary time.A persistent challenge in studying the factors that underlie community assembly is that turnover is dynamic and exhibits nonlinear variation over space and time (10). As a result, different processes may underlie turnover, depending on the scale at which the community is defined (11–13). For instance, numerous studies have asserted that adaptive specialization on abiotic conditions and barriers to dispersal drive regional turnover patterns while biotic interactions filter communities locally (2, 14). Still, the spatial scales of these various processes are uncertain (11, 15, 16), and empirical tests are complicated by the fact that potential drivers of turnover tend to be spatially autocorrelated (17).To determine the drivers and scale of community turnover in complex systems, we need appropriate, nonlinear analytical tools. Generalized dissimilarity models (GDMs) are an extension of matrix regression that provides two notable innovations: 1) GDMs can incorporate various biotic and abiotic predictors into a single model, and 2) GDMs explicitly model the curvilinear relationship between community dissimilarity and ecological or geographic distance (4, 10, 18). This modeling framework is better suited than linear matrix regression to identifying key factors underlying turnover in complex environments (19–21). In addition, by incorporating phylogenetic measures of community diversity and similarity, we can use GDMs to test how drivers of turnover have varied over evolutionary time (22). Comparing “phylogenetic turnover” to species turnover allows us to distinguish deep-time processes that may restrict the ranges of clades from contemporary processes that may constrain the range limits of individual species (2). For example, evolutionary conservation of traits may exclude entire clades from certain habitats, leading to strong phylogenetic turnover over ecological gradients (3). Alternatively, if traits that underpin environmental associations are evolutionarily labile, species turnover will be higher than phylogenetic turnover and better predicted by ecological variation.The tropical Andes provide an ideal natural laboratory for investigating community turnover in response to biotic and abiotic changes in the environment. Habitable elevational gradients spanning more than 5,000 vertical meters encompass rapid changes in vegetation structure, temperature, atmospheric pressure, ultraviolet (UV) exposure, and precipitation (23, 24). The Andean cordillera generates broad orographic precipitation, but its complex topography also creates a patchwork of rain shadows. Rain-shadowed slopes and valleys fragment the ranges of humid and dry-adapted species, particularly those occurring at higher elevations (25–29). Environmental change across elevational gradients of the Andes is exceptionally rapid compared to change along axes parallel to the cordillera. As a result, spatial distance and environmental difference are decoupled. Pairs of communities separated by the same geographic distance may have similar or contrasting environments. In this way, this landscape provides the opportunity to pinpoint environmental effects on community turnover and distinguish them from the effects of dispersal limitation.The Andes are a global hot spot for species richness and turnover, evolutionary distinctness, and small-ranged species (30–33). Species interactions are thought to be particularly important in shaping Andean community turnover: For example, Andean birds are often highly specialized on particular habitats and resources (13, 34), and competitive exclusion is thought to further limit and reinforce range boundaries (7, 35–37). However, parasitism has received less attention as a driver of turnover compared to competition (35, 37) and bird–plant mutualisms (36, 38, 39). One important group that could affect bird turnover is the hemosporidians (Apicomplexa: Haemosporida), a diverse clade of vector-borne parasites in the genera Haemoproteus, Parahaemoproteus, Plasmodium, and Leucocytozoon (40, 41). These parasites can reduce the fitness of their hosts, even in low-level chronic infections (42), and are thought to have the potential to shape avian biogeographic patterns (40, 43). Hemosporidian communities in turn are thought to be influenced to varying degrees by host community, climate, and barriers to dispersal (44–51), but improved modeling frameworks with new data are needed to reciprocally test the causes of host and parasite turnover across biodiverse, tropical landscapes.In this study, we identified and compared the drivers of diversity in interacting bird and hemosporidian communities of the Peruvian Andes. First, we tested whether similar or different drivers affect host and parasite turnover; second, we tested how drivers of turnover vary with spatial scale; and third, we tested how drivers of turnover have changed over evolutionary time. Then, we used a complementary modeling approach to identify sources of variation in species richness among host and parasite communities, respectively. We used these models to map host and parasite turnover and richness to identify hot spots for faunal overlap and transition, critical zones for biodiversity study and protection.