Differential association of cardiorespiratory fitness and central adiposity among US adolescents and adults: A quantile regression approach.

Previous studies assessing the association between cardiorespiratory fitness (CRF) and waist circumference (WC) have often restricted their evaluation to the association of CRF on average WC. Consequently, the assessment of important variations in the relationship of CRF across the WC distribution was precluded. The purpose of this study was to comprehensively evaluate the association between CRF and the distribution of WC using quantile regression. Secondary data analysis was conducted using data from the 1999-2004 NHANES. Participants (n=8260) aged 12-49years with complete data on estimated maximal oxygen consumption and WC were included. Quantile regression models were performed to assess the association between CRF and the 10th, 25th, 50th, 75th and 90th WC percentiles and were adjusted for age and race/ethnicity. For male and female adolescents with high CRF compared to low-fit counterparts, significant negative estimates (2.8 to 20.2cm and 2.3 to 11.2cm, respectively) were observed across most WC percentiles. Similarly, among male and female adults, high CRF was associated with significant reductions in WC across all percentiles (9.5 to 12.0cm and 3.7 to 9.2cm, respectively). For both populations, an increasing trend in the magnitude of the association of high CRF across the WC percentiles was observed. CRF appears to have a differential relationship across the WC distribution with the largest reductions in WC were found among high-fit individuals with the greatest amount of central adiposity (WC≥90th percentile). Additionally, this differential association highlights the significant limitations of statistical techniques used in previous analyses which focused on the center of the distribution.

Gender Disparities in Symptoms of Depression After Medical School Exams and Student Coping Strategies for Postexam Depression Symptoms.

CONTEXT: Little research exists to determine if medical students experience symptoms of depression after examinations and if symptoms vary by gender. OBJECTIVES: Determine if is there a difference between male and female medical students in the number of symptoms of major depressive disorder (MDD) experienced after exams, as well as which coping strategies are used by students to alleviate depression symptoms. METHODS: An anonymous and secure survey was sent via university email to first, second, and third-year medical students after exams for 2 consecutive exam periods. Surveys that were not fully completed were excluded from the analysis. RESULTS: A total of 162 out of 550 students completed the survey for a response rate of 30%. Overall, a greater proportion of female students experienced more symptoms of depression compared to males. This was statistically significant for the Diagnostic and Statistical Manual of Mental Disorders 5th Edition symptoms of MDD: depressed mood, anhedonia, changes in sleep, fatigue, and difficulty with concentration after exams compared to their male counterparts. Male first-year medical students experienced higher rates of depression compared to their third-year counterparts. Most students exhibited coping strategies that helped them feel less depressed. The 3 most common coping strategies reported were: reaching out to social support networks, physical activity/exercise, and engaging in hobbies. CONCLUSIONS: Both gender and year in a medical school play a role in the number of symptoms of depression experienced after medical school exams. Recognizing that examinations can be a trigger of depressive symptoms in medical students, particularly female and first-year students, has important implications on student mental health. Helping students recognize these symptoms and employ healthy coping strategies may further help alleviate these symptoms. Long-term consequences of experiencing symptoms of depression after recurrent exams in medical school are unknown and require further research.

Differential relationships between waist circumference and cardiorespiratory fitness among people with and without type 2 diabetes.

Adults with type 2 diabetes mellitus tend to exhibit an increased level of central adiposity, augmenting their risk of further non-communicable diseases (NCDs). Importantly, consistent evidence demonstrates a significant, negative association between cardiorespiratory fitness (CRF) and waist circumference (WC). However, no previous studies have investigated differences in these CRF-related reductions in WC between adults with and without diabetes. This study used data from the Aerobic Center for Longitudinal Studies, conducted between 1970 and 2006 among predominately Non-Hispanic White, middle-to-upper class adults in Texas. Quantile regression models were used to estimate CRF-related differences in WC between persons with and without diabetes. Age, height, smoking status and birth cohort served as covariates. The analytic sample included 45901 adults. Significantly larger reductions in WC were observed among adults with diabetes as compared to without diabetes across all WC percentiles. Among males, high CRF levels were associated with significant reductions, as compared to their low-fit counterparts, in WC as large as 21.9 cm for adults without diabetes and as large as 27 cm for adults with diabetes. Among females, high CRF levels were associated with significant reductions, as compared to their low-fit counterparts, in WC as large as 22.3 and 30.0 cm for adults without and with diabetes, respectively. This study demonstrated that higher CRF is associated with significant reductions in WC, with greater magnitudes found among adults with diabetes, especially among the most centrally obese, highlighting the necessity of exercise prescription in this clinical population potentially leading to lower risks of future NCDs.

The Role of Energy Intake on Fitness-Adjusted Racial/Ethnic Differences in Central Adiposity Using Quantile Regression.

BACKGROUND: Energy intake (EI) is suggested to be associated with adiposity and may explain previously observed fitness-adjusted racial disparities in waist circumference (WC). OBJECTIVE: The purpose of this study was to comprehensively evaluate the role of EI on the fitness-adjusted racial/ethnic disparities in WC in a nationally representative sample of females using quantile regression. METHODS: Our sample consisted of 3874 female participants (aged 12 to 49 years) from the 1999-2004 National Health and Nutrition Examination Survey. The role of EI was assessed in separate analyses via estimation using a 24-hour dietary recall (DR) and the Institute of Medicine total daily energy expenditure equations. Age-stratified quantile regression models were used to estimate the differences in WC between minority groups and non-Hispanic (NH) white, adjusting for EI, CRF, age, and height. RESULTS: Results from the quantile regression analyses adjusting for EI via DR showed significant differences in WC between NH black and NH white at the 25th-90th WC percentiles (5.9-11.1 cm) for females 20-49 and at the 90th WC percentile (10.1 cm) for females 16-19. For females 12-15, no significant differences were observed between NH black and NH white. Analyses adjusting for EI via IOM showed significant differences in WC between NH black and NH white only for females aged 20-49 years, at the 50th and 75th percentile (1.7-3.6 cm). Compared to NH White, Mexican American females, in all age groups, tended to have significantly greater WC. CONCLUSIONS: These results highlight the importance of rigor in energy intake assessments, suggesting that EI, if adequately assessed, may explain a substantial part of the racial/ethnic differences in WC between NH black and NH white females. Additionally, the observed persistence of estimated differences in WC with advancing age suggests other factors (e.g., hormones) may play a role.