Large contribution of biomass burning emissions to ozone throughout the global remote troposphere.

Ozone is the third most important anthropogenic greenhouse gas after carbon dioxide and methane but has a larger uncertainty in its radiative forcing, in part because of uncertainty in the source characteristics of ozone precursors, nitrogen oxides, and volatile organic carbon that directly affect ozone formation chemistry. Tropospheric ozone also negatively affects human and ecosystem health. Biomass burning (BB) and urban emissions are significant but uncertain sources of ozone precursors. Here, we report global-scale, in situ airborne measurements of ozone and precursor source tracers from the NASA Atmospheric Tomography mission. Measurements from the remote troposphere showed that tropospheric ozone is regularly enhanced above background in polluted air masses in all regions of the globe. Ozone enhancements in air with high BB and urban emission tracers (2.1 to 23.8 ppbv [parts per billion by volume]) were generally similar to those in BB-influenced air (2.2 to 21.0 ppbv) but larger than those in urban-influenced air (-7.7 to 6.9 ppbv). Ozone attributed to BB was 2 to 10 times higher than that from urban sources in the Southern Hemisphere and the tropical Atlantic and roughly equal to that from urban sources in the Northern Hemisphere and the tropical Pacific. Three independent global chemical transport models systematically underpredict the observed influence of BB on tropospheric ozone. Potential reasons include uncertainties in modeled BB injection heights and emission inventories, export efficiency of BB emissions to the free troposphere, and chemical mechanisms of ozone production in smoke. Accurately accounting for intermittent but large and widespread BB emissions is required to understand the global tropospheric ozone burden.

Systematic review of epidemiological studies evaluating the association between exposure to man-made vitreous fibers and non-malignant respiratory diseases.

This study aimed to systematically review and synthesize epidemiological evidence evaluating the association between occupational man-made vitreous fiber (MMVF) exposure and non-malignant respiratory disease (NMRD). We searched PubMed and Scopus databases to identify epidemiological studies evaluating the association between occupational MMVF exposure (limited to insulation wools) and at least 1 NMRD outcome published prior to January 2023. A total of 23 studies met our inclusion criteria. Studies of NMRD mortality among workers with MMVF exposure (n = 9) predominately reported null findings. Qualitative and quantitative synthesis of evidence from these studies suggests that MMVF exposure is not associated with elevated risk of NMRD mortality. The remaining 14 studies evaluated NMRD morbidity, specifically self-reported respiratory symptoms and/or subclinical measures of respiratory disease. Our review did not identify any consistent or compelling evidence of an association between MMVF exposure and any NMRD morbidity outcome; however, this body of evidence was largely limited by cross-sectional design, self-reported exposure and/or outcome ascertainment, incomplete statistical analysis and reporting, and questionable generalizability given that 13/14 studies were published over 20 years ago. We recommend that future studies aim to overcome the limitations of this literature to more accurately characterize the association between occupational MMVF exposure and NMRD morbidity.

Rapid hydrolysis of tertiary isoprene nitrate efficiently removes NOx from the atmosphere.

The formation of a suite of isoprene-derived hydroxy nitrate (IHN) isomers during the OH-initiated oxidation of isoprene affects both the concentration and distribution of nitrogen oxide free radicals (NOx). Experiments performed in an atmospheric simulation chamber suggest that the lifetime of the most abundant isomer, 1,2-IHN, is shortened significantly by a water-mediated process (leading to nitric acid formation), while the lifetime of a similar isomer, 4,3-IHN, is not. Consistent with these chamber studies, NMR kinetic experiments constrain the 1,2-IHN hydrolysis lifetime to less than 10 s in deuterium oxide (D2O) at 298 K, whereas the 4,3-IHN isomer has been observed to hydrolyze much less efficiently. These laboratory findings are used to interpret observations of the IHN isomer distribution in ambient air. The IHN isomer ratio (1,2-IHN to 4,3-IHN) in a high NOx environment decreases rapidly in the afternoon, which is not explained using known gas-phase chemistry. When simulated with an observationally constrained model, we find that an additional loss process for the 1,2-IHN isomer with a time constant of about 6 h best explains our atmospheric measurements. Using estimates for 1,2-IHN Henry's law constant and atmospheric liquid water volume, we show that condensed-phase hydrolysis of 1,2-IHN can account for this loss process. Simulations from a global chemistry transport model show that the hydrolysis of 1,2-IHN accounts for a substantial fraction of NOx lost (and HNO3 produced), resulting in large impacts on oxidant formation, especially over forested regions.

Exposure to MMVF in residential and commercial buildings: A literature review and quantitative synthesis.

Man-made vitreous fibers (MMVF) are a class of inorganic fibrous materials that include glass and mineral wools, continuous glass filaments, and refractory ceramic fibers valued for their insulative properties in high temperature applications. Potential health effects from occupational exposure to MMVF have been investigated since the 1970s, with focus on incidence of respiratory tract cancer among MMVF-exposed production workers. The general population may experience exposure to MMVF in residential and/or commercial buildings due to deterioration, construction, or other disruption of materials containing these fibers. Numerous studies have characterized potential exposures that may occur during material disruption or installation; however, fewer have aimed to measure background MMVF concentrations in residential and commercial spaces (i.e., non-production settings) to which the general population may be exposed. In this study, we reviewed and synthesized peer-reviewed studies that evaluated respirable MMVF exposure levels in non-production, indoor environments. Among studies that analyzed airborne respirable MMVF concentrations, 110-fold and 1.5-fold differences in estimated concentrations were observed for those studies utilizing phase contrast optical microscopy (PCOM) versus transmission electron microscopy (TEM) and scanning electron microscopy (SEM), respectively. A positive correlation was observed between respirable air concentrations of MMVF and total surface concentrations of MMVF in seldom-cleaned areas. Ultimately, available evidence suggests that both ambient air and surface concentrations of MMVF in indoor environments are consistently lower than exposure limits developed to prevent negative health outcomes among sensitive populations.

Yields of HONO2 and HOONO Products from the Reaction of HO2 and NO Using Pulsed Laser Photolysis and Mid-Infrared Cavity-Ringdown Spectroscopy.

The reaction of HO2 with NO is one of the most important steps in radical cycling throughout the stratosphere and troposphere. Previous literature experimental work revealed a small yield of nitric acid (HONO2) directly from HO2 + NO. Atmospheric models previously treated HO2 + NO as radical recycling, but inclusion of this terminating step had large effects on atmospheric oxidative capacity and the concentrations of HONO2 and ozone (O3), among others. Here, the yield of HONO2, φHONO2, from the reaction of HO2 + NO was investigated in a flow tube reactor using mid-IR pulsed-cavity ringdown spectroscopy. HO2, produced by pulsed laser photolysis of Cl2 in the presence of methanol, reacted with NO in a buffer gas mixture of N2 and CO between 300 and 700 Torr at 278 and 300 K. HONO2 and its weakly bound isomer HOONO were directly detected by their v1 absorption bands in the mid-IR region. CO was used to suppress HONO2 produced from OH + NO2 and exploit a chemical amplification scheme, converting OH back to HO2. Under the experimental conditions described here, no evidence for the formation of either HONO2 or HOONO was observed from HO2 + NO. Using a comprehensive chemical model, constrained by observed secondary reaction products, all HONO2 detected in the system could be accounted for by OH + NO2. At 700 ± 14 Torr and 300 ± 3 K, φHONO2 = 0.00 ± 0.11% (2σ) with an upper limit of 0.11%. If all of the observed HONO2 was attributed to the HO2 + NO reaction, φHONO2 = 0.13 ± 0.07% with an upper limit of 0.20%. At 278 ± 2 K and 718 ± 14 Torr, we determine an upper limit, φHONO2 ≤ 0.37%. Our measurements are significantly lower than those previously reported, lying outside of the uncertainty of the current experimental and recommended literature values.

Assessment of ethanol exposure from hand sanitizer use and potential for developmental toxicity in nursing infants.

Ingestion of ethanol during pregnancy is known to have detrimental effects on the fetus. Although the potential developmental effects of maternal ethanol intake during lactation are less well characterized, public health guidelines recommend avoidance of alcohol or, if alcohol is consumed, to allow for 1-2 h to pass before nursing. A proposal to classify ethanol as potentially harmful to breast-fed children warrants an investigation of the potential adverse neurodevelopmental effects of low-dose ethanol exposure during lactation. There currently are no studies that have examined neurodevelopmental outcomes from lactational exposure to ethanol from the use of topical products that contain ethanol, such as alcohol-based hand sanitizers (ABHS). Furthermore, the epidemiological literature of lactational ethanol exposures from maternal alcohol consumption is limited in design, provides equivocal evidence of neurological effects in infants, and is insufficient to characterize a dose-response relationship for developmental effects. Toxicological studies that observed neurodevelopmental effects in pups from ethanol via lactation did so at exceedingly high doses that also caused maternal toxicity. In this investigation, blood ethanol concentrations (BECs) of breastfeeding women following typical-to-intense ABHS use were computationally predicted and compared to health benchmarks to quantify the risk for developmental outcomes. Margins of 2.2 to 1000 exist between BECs associated with ABHS use compared to BECs associated with neurotoxicity adverse effect levels in the toxicology literature or oral ethanol intake per public health guidelines. Neurodevelopmental effects are not likely to occur in infants due to ABHS use by breastfeeding women, even when ABHSs are used at intense frequencies.

Assessment of formaldehyde exposures under contemporary embalming conditions in U.S. funeral homes.

The funeral service profession has used formaldehyde-containing embalming solutions for the preparation of decedents since the early 1900s. The available literature regarding funeral director exposure to formaldehyde largely consists of data collected prior to 2000, with most studies reporting task-length exposure concentrations rather than full-shift time-weighted average concentrations. As formaldehyde undergoes review in the U.S. Environmental Protection Agency Toxic Substances Control Act (TSCA) risk evaluation process, accurately characterizing long-term exposure potential in this profession is critical. This study presents passive badge sampling and air change rate measurement results conducted at 13 funeral home locations across the United States. Full-shift (approximately 8-hr) samples were collected on one embalmer per day in each funeral home and on one occupational non-user (ONU), e.g., a receptionist. Additionally, task-length samples were collected during each embalming that occurred during the shift, were one to occur. Full-shift concentrations ranged from 0.007 to 1.1 ppm and 0.007 to 0.042 ppm for embalmers and ONUs, respectively. Task-length formaldehyde concentrations ranged from 0.058 to 1.4 ppm, with the average embalming taking 72.8 min to complete. Air change rates in the preparation rooms ranged from 2.8 to 28.3 air changes per hour; however, no correlation between task-length formaldehyde concentrations and air change rate was observed. Following empirical data collection, a Monte Carlo analysis of estimated annual 8-hr time-weighted average (TWA) exposure was conducted to determine the potential exposure distribution for embalmers employed at private funeral homes. Inputs to the simulation were derived from responses to a National Funeral Directors Association survey and from empirical measurements collected during the study. With respect to the reconstructed 8-hr TWAs, the median 8-hr TWA was 0.037 ppm, with 93.6% of the predicted concentrations below 0.1 ppm. This study provides a robust characterization of contemporary formaldehyde exposures in the funeral service profession. Further, it provides a strategy for interpreting the results along with surveyed responses regarding embalming frequency to better inform risks associated with formaldehyde exposure in this profession.

Stress and Burnout Among Graduate Students: Moderation by Sleep Duration and Quality.

BACKGROUND: There are high levels of stress among graduate students, and stress is associated with multiple negative outcomes among student populations, including academic burnout. Sleep could play an important role in explaining the association between stress and burnout, but these relationships have not been explored among the graduate student population. The current study assessed whether or not sleep duration and quality moderated the relationship between stress and burnout (i.e., exhaustion, cynicism, and inefficacy) among graduate students. METHODS: A sample of 2683 master's, doctoral, and professional graduate students from two large, public universities completed an online survey. Linear regression models with interaction terms were developed to evaluate the relationships between stress and burnout while examining moderation by sleep duration and quality. RESULTS: Participants slept an average of 6.4 h per night, with 62% indicating good sleep quality. Stress had significant, positive relationships with exhaustion, cynicism, and inefficacy. The relationship between stress and exhaustion lessened as sleep duration increased, and the relationship between stress and exhaustion was weaker among students with good sleep quality when compared with those with poor sleep quality. Neither sleep duration nor sleep quality moderated the relationships between stress and cynicism or stress and inefficacy. CONCLUSIONS: Improving sleep habits has the potential to lessen the negative association between stress and graduate student functioning. Future research utilizing longitudinal designs is needed to understand the temporality of these associations and the influence of possible co-factors like individual propensity for mental health problems and social support.

Age-varying trends in alcohol and cannabis co-occurring use: Implications for prescription drug misuse.

Background: Individuals who engage in alcohol and cannabis co-occurring use are at heightened risk for negative outcomes than individuals who only use alcohol or only use cannabis, but far less is known about implications of alcohol and cannabis co-occurring use for prescription drug misuse (PDM).Objectives: This study aimed to (1) identify whether co-occurring use was linked with greater risk for PDM across ages 18-60 and to determine ages at which this association was strongest, (2) determine whether associations remain after controlling for pain severity, and (3) test for gender differences.Methods: Cross-sectional data were from Wave 1 of the Population Assessment of Tobacco and Health (PATH) study. The analytic sample included 20,120 (50.6%wt men) individuals aged 18-60 reporting past-year alcohol and/or cannabis use.Results: Time-varying effect models indicated that individuals reporting co-occurring use were at increased risk for PDM than individuals reporting single-substance use across all ages, with odds ratios peaking at >3 at age 34. After controlling for pain severity, associations were only slightly weakened. Associations were slightly stronger for men than women from ages 28 to 35.Conclusion: Co-occurring use was linked with heightened risk for PDM compared to individuals who used only one substance; co-occurring use may be important to target for PDM prevention. Identifying factors underlying study associations, beyond pain, and how these factors evolve with age are important avenues for prevention work.

Nonmedical Use of Prescription Stimulants as a "Red Flag" for Other Substance Use.

BACKGROUND: Nonmedical use of prescription stimulants (NMPS) has increased on college campuses during the past two decades. NMPS is primarily driven by academic enhancement motives, and normative misperceptions exist as well. However, large, nationwide studies have not yet been conducted to generalize findings more broadly and gain a deeper understanding of the relationship between NMPS and other substance use (e.g. alcohol use, marijuana, etc.). The present study was conducted to lay the foundation for prevention efforts related to NMPS by establishing NMPS prevalence, practices surrounding NMPS, and other substance use. METHODS: N = 2,989 students from seven universities around the U.S. completed a web-based survey assessing NMPS practices and related behaviors. Prevalence and factors associated with NMPS were explored. RESULTS: Analyses revealed a 17% past-year prevalence of NMPS with associated widespread misperceptions of peer use. NMPS was significantly related to alcohol use, binge drinking, and marijuana use, as well as skipped classes and affiliation with Greek life. CONCLUSIONS: Although most college students do not report NMPS, those who do also are more likely to report alcohol use, binge drinking, and marijuana use, and NMPS could be a "red flag" for other risk behaviors worth exploring. Implications for prevention and intervention are discussed.

PROFILES OF ALCOHOL AND MARIJUANA USE AMONG SIMULTANEOUS ALCOHOL AND MARIJUANA USERS: INDIVIDUAL DIFFERENCES IN DEMOGRAPHICS AND SUBSTANCE USE.

Simultaneous alcohol and marijuana (SAM) use - or use of both substances with overlapping effects - is common among emerging adults and is linked to increased risk for problematic substance use outcomes. The current study identified subgroups of emerging adult SAM users based on their typical alcohol and marijuana use patterns and compared groups on key individual characteristics. Latent profile analysis uncovered four profiles of SAM users (n=522): Light Users (LU; 49.0%), Moderate Drinkers with Frequent Marijuana Use (MDFM; 37.9%), Moderate Drinkers with High Peak Levels (MDHP; 5.4%), and Heavy/Frequent Users (HFU; 7.7%). Group differences by demographic characteristics were found, with LU more likely to be college attendees/graduates than MDFM. Additionally, HFU were more likely to be Greek-affiliated than both LU and MDFM. Groups also differed based on other drug use behavior and preferred route of marijuana administration. Findings demonstrate diversity among SAM users based on typical substance use patterns.

Social context of drinking among older adults: Relationship to alcohol and traffic risk behaviors.

OBJECTIVE: Alcohol use among older adults is a major public health concern given potentially negative effects to health and functioning in this population. Little is known about context in which alcohol use among older adults occurs, or how context of use is associated with risk behaviors. METHOD: Invitation letters were mailed to licensed drivers 65 years and older in Maryland. A total of 825 participants completed an online survey that assessed demographic characteristics, alcohol use, social context of drinking, and driving behaviors. RESULTS: The analytic sample consisted of 604 older adult current drinkers (55% male). A factor analysis revealed three separate contexts of drinking: social facilitation, emotional comfort, and relaxation. Drinking in the context of social facilitation was associated with driving after drinking. Drinking in the context of emotional comfort was associated with getting drunk, driving after drinking, and running a stop sign or red light. Drinking in the context of relaxation was associated with traffic risk behaviors, including running a stop sign or red light and getting in a near crash or collision. CONCLUSIONS: Understanding the social context of alcohol use among older adults may be useful for targeting and attempting to modify risky alcohol use and driving behaviors.

Kinetics and Product Yields of the OH Initiated Oxidation of Hydroxymethyl Hydroperoxide.

Hydroxymethyl hydroperoxide (HMHP), formed in the reaction of the C1 Criegee intermediate with water, is among the most abundant organic peroxides in the atmosphere. Although reaction with OH is thought to represent one of the most important atmospheric removal processes for HMHP, this reaction has been largely unstudied in the laboratory. Here, we present measurements of the kinetics and products formed in the reaction of HMHP with OH. HMHP was oxidized by OH in an environmental chamber; the decay of the hydroperoxide and the formation of formic acid and formaldehyde were monitored over time using CF3O- chemical ionization mass spectrometry (CIMS) and laser-induced fluorescence (LIF). The loss of HMHP by reaction with OH is measured relative to the loss of 1,2-butanediol [ k1,2-butanediol+OH = (27.0 ± 5.6) × 10-12 cm3 molecule-1s-1]. We find that HMHP reacts with OH at 295 K with a rate coefficient of (7.1 ± 1.5) × 10-12 cm3 molecule-1s-1, with the formic acid to formaldehyde yield in a ratio of 0.88 ± 0.21 and independent of NO concentration (3 × 1010 - 1.5 × 1013 molecules cm-3). We suggest that, exclusively, abstraction of the methyl hydrogen of HMHP results in formic acid, while abstraction of the hydroperoxy hydrogen results in formaldehyde. We further evaluate the relative importance of HMHP sinks and use global simulations from GEOS-Chem to estimate that HMHP oxidation by OH contributes 1.7 Tg yr-1 (1-3%) of global annual formic acid production.

Immediate effects of a brief intervention to prevent alcohol and medication interactions among older adults.

Risk of experiencing alcohol and medication interactions (AMI) is significant among older adults due to the substantial prevalence of alcohol and medication use in this segment of the population. Given the lack of community-level AMI prevention interventions for older adults, this study aimed to examine the immediate effects of a brief, pharmacy-based intervention to prevent AMI among older adults, as well as assess differential effects by past-month drinking status. A convenience sample of 134 adults aged 59 and older was recruited from four pharmacies in rural Virginia. Participants were assessed on their AMI awareness, intentions and importance prior to and immediately after exposure to intervention materials. Findings support immediate, positive intervention effects on AMI awareness, intentions and perceived importance of AMI messaging. Changes from pre to post-test did not differ by drinking status, but participants who consumed alcohol were less likely than non-drinkers to recognize the potential consequential severity of alcohol and medication interactions at both time points. Recommendations and future research to prevent AMI are discussed.

Prevalence and incidence of drug use among college students: an 8-year longitudinal analysis.

BACKGROUND: Drug use among college students is associated with adverse academic and health outcomes and risks to personal safety. OBJECTIVES: This study utilized data from a longitudinal study to estimate annual prevalence, cumulative lifetime prevalence, and incidence of ten types of drug use during the eight years after college entry and the average age of onset of each drug used. METHODS: Participants (N = 1,253; 52% female) were young adults who were originally enrolled as first-time, first-year students at a university in the mid-Atlantic US. Annual personal interviews gathered data about the use of seven illicit drugs and three prescription drugs used nonmedically. Annual follow-up rates ranged from 76 to 91%. RESULTS: Marijuana was the most commonly used drug in every year of the study, with the highest annual prevalence estimates in Year 3 (47%wt). In Year 8, when the modal age of participants was 25, 29%wt used marijuana during the past year. Nonmedical use of prescription drugs was more prevalent during college than in the later years of the study. Although the prevalence of cocaine and ecstasy use was low (cumulative prevalence estimates of 17%wt and 13%wt, respectively), incidence for these drugs was particularly high in the later years of the study. CONCLUSION: Drug use is prevalent among college students, and drug use persists among young adults, even after many have graduated college. More attention should be directed at identifying and intervening with students at risk for drug use to mitigate possible academic, health, and safety consequences.

Drinking Like an Adult? Trajectories of Alcohol Use Patterns Before and After College Graduation.

BACKGROUND: College students who engage in high-risk drinking patterns are thought to "mature out" of these patterns as they transition to adult roles. College graduation is an important milestone demarcating this transition. We examine longitudinal changes in quantity and frequency of alcohol consumption between the college years and the 4 years after graduation and explore variation in these changes by gender and race/ethnicity. METHODS: Participants were 1,128 college graduates enrolled in a longitudinal prospective study of health-risk behaviors. Standard measures of alcohol consumption were gathered during 8 annual personal interviews (76 to 91% annual follow-up). Graduation dates were culled from administrative data and self-report. Spline models, in which separate trajectories were modeled before and after the "knot" of college graduation, were fit to 8 annual observations of past-year alcohol use frequency and quantity (typical number of drinks/drinking day). RESULTS: Frequency increased linearly pregraduation, slightly decreased postgraduation, and then rebounded to pregraduation levels. Pregraduation frequency increased more steeply among individuals who drank more heavily at college entry. Quantity decreased linearly during college, followed by quadratic decreases after graduation. CONCLUSIONS: Results suggest that the postcollege "maturing-out" phenomenon might be attributable to decreases in alcohol quantity but not frequency. High-frequency drinking patterns that develop during college appear to persist several years postgraduation.

Age-varying association between depression symptoms and executive function among older adults: Moderation by physical activity.

OBJECTIVES: This study assessed trends in depression symptoms, executive function, and their association across age among older adults. Subgroup comparisons were made between older adults meeting and not meeting physical activity guidelines on variables and associations of interest. METHODS: Participants (n = 2473) were older adults ages 60 to 79 from the 2011-2014 National Health and Nutrition Examination Survey. Depression symptoms, executive function, and physical activity were assessed, and weighted time-varying effect modeling was used for analyses. RESULTS: Depression symptoms were most severe at age 62 followed by a modest decline before a second peak around age 67. Executive function was highest at age 60 and declined steadily through age 77. Depression symptoms and executive function were negatively associated, but the strength and significance of this association varied with age. Older adults meeting physical activity guidelines had increased executive function and less severe depression symptoms, and meeting physical activity guidelines buffered the association between depression symptoms and executive function at key ages during older adulthood. CONCLUSIONS: Differences by age should be considered when designing and implementing health programs and treatments focusing on mental health and cognition in older adulthood. Encouraging moderate-intensity physical activity may help protect older adults from depression-related cognitive decline.

High-risk alcohol use behavior and daily academic effort among college students.

Objective It is not well understood whether heavy drinking interferes with academics on specific days or if this relationship simply reflects between-student differences. Participants:N = 736 college students completed 14 consecutive daily assessments during 7 semesters. Methods: Days were classified as non-drinking, moderate drinking, heavy episodic drinking only (HED-only), or high-intensity drinking (HID) days. Multilevel models tested associations between drinking level and academic behaviors. Results: Students were more likely to skip class after engaging in HED-only or HID the previous day. On weekdays, students spent more time on schoolwork when they did not drink the previous day and spent less time on schoolwork when they engaged in HED-only and HID the previous day. On weekends, students spent less time on schoolwork after HED-only days. Conclusions: Heavy drinking is associated with lower academic effort the next day, highlighting the need for college programs targeting heavy alcohol use prevention and daily decision making.

Graduate student burnout: Substance use, mental health, and the moderating role of advisor satisfaction.

Substance use and mental health problems are associated with academic difficulties among high school and undergraduate students, but little research has been conducted on these relationships among graduate students. The sample consisted of 2,683 graduate students attending two large, public universities. Standard measures were used to collect data on demographic and program characteristics, mental health, substance use, advisor satisfaction, and burnout (i.e., exhaustion, cynicism, and inefficacy). Linear regression models evaluated relationships between each mental health and substance use variable with burnout, as well as the moderating role of advisor satisfaction. Students with a greater number of substance use and mental health problems had higher levels of exhaustion, cynicism, and inefficacy. No statistically significant relationships between substance use and burnout were found. High levels of stress, moderate or severe anxiety symptoms, and moderate or severe depressive symptoms were associated with increased levels of burnout. Advisor support moderated the relationships between stress and both cynicism and inefficacy such that the effects of stress on these dimensions of burnout were lower among those who were satisfied with their advisor. Graduate students with mental health problems might be at increased risk for burnout; however, having a supportive advisor might buffer this association.

BDNF Val66Met Polymorphism Reduces the Fatigue-Like Effects of 5-Fluorouracil on Voluntary Wheel-Running Activity in Mice.

Fatigue is a persistent and debilitating symptom following cancer treatments such as chemotherapy. Recent clinical studies have suggested a common single-nucleotide polymorphism of brain-derived neurotrophic factor (BDNF), Val66Met (rs6265), may be related to the severity of fatigue following cancer treatment. In this study, we tested transgenic mice homozygous for the human Val66Met BDNF gene and wild-type controls. We injected three doses of 5-fluorouracil (5FU) as a model of chemotherapy treatment, and we used changes in voluntary wheel running activity (VWRA) as a measure of fatigue-like behavior. Prior to 5FU injection, we found that during the baseline wheel-running period, the Val66Met mice lost more weight than WT controls. We next administered 5FU and saw a robust fatigue-like phenotype that lasted about 2 weeks. During the first week, the fatigue-like phenotype was less severe in the Val66Met mice and unrelated to the age of the mice. In contrast, during the second week after 5FU treatment, the fatigue-like phenotype was unrelated to the BDNF genotype but was more severe in middle aged mice compared to young mice. We conclude that the BDNF polymorphism may play a direct, protective role against chemotherapy-induced fatigue.