Ananda Sen

The Theory of Dispersion Models

Introduction to dispersion models natural exponential families exponential dispersion models tweedie models proper dispersion models.

Resistance Exercise for Muscular Strength in Older Adults: A Meta-Analysis

PURPOSE The effectiveness of resistance exercise for strength improvement among aging persons is inconsistent across investigations, and there is a lack of research synthesis for multiple strength outcomes. METHODS The systematic review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) recommendations. A meta-analysis was conducted to determine the effect of resistance exercise (RE) for multiple strength outcomes in aging adults. Randomized-controlled trials and randomized or non-randomized studies among adults > or = 50 years, were included. Data were pooled using random-effect models. Outcomes for 4 common strength tests were analyzed for main effects. Heterogeneity between studies was assessed using the Cochran Q and I(2) statistics, and publication bias was evaluated through physical inspection of funnel plots as well as formal rank-correlation statistics. A linear mixed model regression was incorporated to examine differences between outcomes, as well as potential study-level predictor variables. RESULTS Forty-seven studies were included, representing 1079 participants. A positive effect for each of the strength outcomes was determined however there was heterogeneity between studies. Regression revealed that higher intensity training was associated with greater improvement. Strength increases ranged from 9.8 to 31.6 kg, and percent changes were 29+/-2, 24+/-2, 33+/-3, and 25+/-2, respectively for leg press, chest press, knee extension, and lat pull. CONCLUSIONS RE is effective for improving strength among older adults, particularly with higher intensity training. Findings therefore suggest that RE may be considered a viable strategy to prevent generalized muscular weakness associated with aging.

A meta-analysis of pedometer-based walking interventions and weight loss

PURPOSE Cross-sectional studies show that individuals who walk more tend to be thinner than those who walk less. This does not mean, however, that the association between higher step counts and lower weight is causal or that encouraging sedentary individuals to increase step counts helps them lose weight. METHODS In this meta-analysis, we searched 6 electronic databases and contacted pedometer experts to identify pedometer-based walking studies without a dietary intervention that reported weight change as an outcome. We included randomized controlled trials and prospective cohort studies published after January 1, 1995, in either English or Japanese, with 5 or more adult participants and at least 1 cohort enrolled in a pedometer-based walking intervention lasting at least 4 weeks. RESULTS Nine studies met the study inclusion criteria. Cohort sample size ranged from 15 to 106, for a total of 307 participants, 73% of whom were women and 27% of whom were men. The duration of the intervention ranged from 4 weeks to 1 year, with a median duration of 16 weeks. The pooled estimate of mean weight change from baseline using a fixed-effects model and combining data from all 9 cohorts was −1.27 kg (95% confidence interval, −1.85 to −0.70 kg). Longer intervention duration was associated with greater weight change. On average, participants lost 0.05 kg per week during the interventions. CONCLUSION Pedometer-based walking programs result in a modest amount of weight loss. Longer programs lead to more weight loss than shorter programs.

Influence of Resistance Exercise on Lean Body Mass in Aging Adults: A Meta-Analysis

PURPOSE sarcopenia plays a principal role in the pathogenesis of frailty and functional impairment that occur with aging. There are few published accounts that examine the overall benefit of resistance exercise (RE) for lean body mass (LBM) while considering a continuum of dosage schemes and/or age ranges. Therefore, the purpose of this meta-analysis was to determine the effects of RE on LBM in older men and women while taking these factors into consideration. METHODS this study followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses recommendations. Randomized controlled trials and randomized or nonrandomized studies among adults ≥ 50 yr were included. Heterogeneity between studies was assessed using the Cochran Q and the I statistics, and publication bias was evaluated through physical inspection of funnel plots as well as formal rank-correlation statistics. Mixed-effects meta-regression was incorporated to assess the relationship between RE dosage and changes in LBM. RESULTS data from 49 studies, representing a total of 1328 participants, were pooled using random-effect models. Results demonstrated a positive effect for LBM, and there was no evidence of publication bias. The Cochran Q statistic for heterogeneity was 497.8, which was significant (P < 0.01). Likewise, I was equal to 84%, representing rejection of the null hypothesis of homogeneity. The weighted pooled estimate of mean LBM change was 1.1 kg (95% confidence interval = 0.9-1.2 kg). Meta-regression revealed that higher-volume interventions were associated (β = 0.05, P < 0.01) with significantly greater increases in LBM, whereas older individuals experienced less increase (β = -0.03, P = 0.01). CONCLUSIONS RE is effective for eliciting gains in LBM among aging adults, particularly with higher-volume programs. Findings suggest that RE participation earlier in life may provide superior effectiveness.

Elevated Insular Glutamate in Fibromyalgia Is Associated With Experimental Pain

OBJECTIVE Central pain augmentation resulting from enhanced excitatory and/or decreased inhibitory neurotransmission is a proposed mechanism underlying the pathophysiology of functional pain syndromes such as fibromyalgia (FM). Multiple functional magnetic resonance imaging studies implicate the insula as a region of heightened neuronal activity in this condition. Since glutamate (Glu) is a major cortical excitatory neurotransmitter that functions in pain neurotransmission, we undertook this study to test our hypothesis that increased levels of insular Glu would be present in FM patients and that the concentration of this molecule would be correlated with pain report. METHODS Nineteen FM patients and 14 age- and sex-matched pain-free controls underwent pressure pain testing and a proton magnetic resonance spectroscopy session in which the right anterior insula and right posterior insula were examined at rest. RESULTS Compared with healthy controls, FM patients had significantly higher levels of Glu (mean +/- SD 8.09 +/- 0.72 arbitrary institutional units versus 6.86 +/- 1.29 arbitrary institutional units; P = 0.009) and combined glutamine and Glu (i.e., Glx) (mean +/- SD 12.38 +/- 0.94 arbitrary institutional units versus 10.59 +/- 1.48 arbitrary institutional units; P = 0.001) within the right posterior insula. No significant differences between groups were detected in any of the other major metabolites within this region (P > 0.05 for all comparisons), and no group differences were detected for any metabolite within the right anterior insula (P > 0.11 for all comparisons). Within the right posterior insula, higher levels of Glu and Glx were associated with lower pressure pain thresholds across both groups for medium pain (for Glu, r = -0.43, P = 0.012; for Glx, r = -0.50, P = 0.003). CONCLUSION Enhanced glutamatergic neurotransmission resulting from higher concentrations of Glu within the posterior insula may play a role in the pathophysiology of FM and other central pain augmentation syndromes.

Optimal step-stress test under progressive type-I censoring

We consider in this work a k-step-stress accelerated test with equal duration steps /spl tau/. Censoring is allowed at each change stress point i/spl tau/, i=1,...k. The problem of choosing the optimal /spl tau/ is addressed using variance optimality as well as determinant-optimality criteria. We investigate in detail the case of progressively Type-I right censored data with a single stress variable.

A randomized trial comparing structured and lifestyle goals in an internet-mediated walking program for people with type 2 diabetes

BackgroundThe majority of individuals with type 2 diabetes do not exercise regularly. Pedometer-based walking interventions can help; however, pedometer-based interventions targeting only total daily accumulated steps might not yield the same health benefits as physical activity programs specifying a minimum duration and intensity of physical activity bouts.MethodsThis pilot randomized trial compared two goal-setting strategies: 1) lifestyle goals targeting total daily accumulated step counts and 2) structured goals targeting bout steps defined as walking that lasts for 10 minutes or longer at a pace of at least 60 steps per minute. We sought to determine which goal-setting strategy was more effective at increasing bout steps. Participants were sedentary adults with type 2 diabetes. All participants: wore enhanced pedometers with embedded USB ports; uploaded detailed, time-stamped step-count data to a website called Stepping Up to Health; and received automated step-count feedback, automatically calculated goals, and tailored motivational messages throughout the six-week intervention. Only the automated goal calculations and step-count feedback differed between the two groups. The primary outcome of interest was increase in steps taken during the previously defined bouts of walking (lasting at least 10 minutes or longer at a pace of at least 60 steps per minute) between baseline and end of the intervention.ResultsThirty-five participants were randomized and 30 (86%) completed the pilot study. Both groups significantly increased bout steps, but there was no statistically significant difference between groups. Among study completers, bout steps increased by 1921 ± 2729 steps a day. Those who received lifestyle goals were more satisfied with the intervention (p = 0.006) and wore the pedometer more often (p < 0.001) than those who received structured goals.ConclusionIn this six-week intervention, Lifestyle Goals group participants achieved increases in bout steps comparable to the increases seen in the Structured Goals group, representing almost a mile a day of additional moderate intensity bout activity. Pedometer-based walking programs that emphasize total accumulated step counts are more acceptable to participants and are as effective at increasing moderate intensity bouts of physical activity as programs that use structured goals.Trial registrationNCT00151021

Predialysis serum sodium level, dialysate sodium, and mortality in maintenance hemodialysis patients: the Dialysis Outcomes and Practice Patterns Study (DOPPS).

BACKGROUND Predialysis serum sodium concentrations recently have been linked to patient characteristics and outcomes in hemodialysis patients and may have implications for the dialysate sodium prescription. STUDY DESIGN Prospective cohort study. PARTICIPANTS 11,555 patients from 12 countries in the Dialysis Outcomes and Practice Patterns Study (DOPPS), phases I (1996-2001) and III (2005-2008). PREDICTORS Demographics, comorbid conditions, laboratory measurements (model 1); mean serum sodium level, dialysate sodium concentration (model 2). OUTCOMES Serum sodium level, using adjusted linear mixed models (model 1); all-cause mortality, using Cox proportional hazards models (model 2). RESULTS Median follow-up was 12 months, with 1,727 deaths (15%) occurring during the study period (12,274 patient-years). Mean serum sodium level in the DOPPS countries was 138.5 ± 2.8 mEq/L. Japan had the highest (139.1 ± 2.6 mEq/L) and Australia/New Zealand had the lowest mean serum sodium level (137.4 ± 2.8 mEq/L). Serum sodium level was associated positively with male sex, black race, body mass index, serum albumin level, and creatinine level and negatively with neurologic and psychiatric disease, white blood cell count, and intradialytic weight loss (0.16 mEq/L lower per 1% loss). Higher serum sodium level was associated with lower adjusted all-cause mortality in a continuous model (HR, 0.95 per 1 mEq/L higher; 95% CI, 0.93-0.97). Dialysate sodium prescription was not associated with serum sodium level. Mortality analyses restricted to the serum sodium tertile with the highest mortality (serum sodium <137 mEq/L) showed lower mortality risk in patients with dialysate sodium prescriptions >140 mEq/L. LIMITATIONS Causality cannot be established in this observational study, which does not consider potential effects of dialysate sodium level on postdialysis thirst, dietary salt and water intake, interdialytic weight gain, and cardiovascular stability. CONCLUSIONS Lower serum sodium levels are associated with certain hemodialysis patient characteristics and higher adjusted risk of death. The lower mortality observed in our adjusted analyses in patients with serum sodium levels <137 mEq/L dialyzed against dialysate sodium prescriptions >140 mEq/L is intriguing, may be related to intradialytic cardiovascular stability, and deserves further study.

Effect of Preventive Messages Tailored to Family History on Health Behaviors: The Family Healthware Impact Trial

PURPOSE We wanted to determine the impact of automated family history assessment and tailored messages for coronary heart disease, stroke, diabetes, colorectal, breast, and ovarian cancer on preventive behaviors compared with a standard preventive message. METHODS The study was a cluster-randomized clinical trial that included 41 primary care practices, the majority in the Midwest, using Family Healthware, a self-administered, Web-based tool that assesses familial risk for the diseases and provides personalized risk-tailored messages. Patients in the control group received an age- and sex-specific health message related to lifestyle and screening. Smoking cessation, fruit and vegetable intake, physical activity, aspirin use, blood pressure, and cholesterol and blood glucose screening were assessed at baseline and 6 months after the intervention. RESULTS Of 4,248 participants, 3,344 (78%) completed the study. Participants were white (91%), female (70%), and insured (97%), and had a mean age of 50.6 years (range 35–65 years). Intervention participants were more likely to increase daily fruit and vegetable consumption from 5 or fewer servings a day to 5 or more servings a day (OR = 1.29; 95% confidence interval [CI], 1.05–1.58) and to increase physical activity (OR = 1.47; 95% CI, 1.08–1.98) to 5 to 6 times a week for 30 minutes or more a week. The absolute differences in proportion were 3% and 4%, respectively. Intervention participants were less likely to move from not having cholesterol screening in the last 5 years to having their cholesterol measured within 5 years (OR = 0.34; 95% CI, 0.17–0.67), with an absolute difference of 15%. CONCLUSIONS Messages tailored to an individual’s familial risk for 6 common diseases modestly increased self-reported physical activity and fruit and vegetable intake but reduced the likelihood of receiving cholesterol screening.

Clinical Practice Guidelines on the Use of Integrative Therapies as Supportive Care in Patients Treated for Breast Cancer

BACKGROUND The majority of breast cancer patients use complementary and/or integrative therapies during and beyond cancer treatment to manage symptoms, prevent toxicities, and improve quality of life. Practice guidelines are needed to inform clinicians and patients about safe and effective therapies. METHODS Following the Institute of Medicines guideline development process, a systematic review identified randomized controlled trials testing the use of integrative therapies for supportive care in patients receiving breast cancer treatment. Trials were included if the majority of participants had breast cancer and/or breast cancer patient results were reported separately, and outcomes were clinically relevant. Recommendations were organized by outcome and graded based upon a modified version of the US Preventive Services Task Force grading system. RESULTS The search (January 1, 1990-December 31, 2013) identified 4900 articles, of which 203 were eligible for analysis. Meditation, yoga, and relaxation with imagery are recommended for routine use for common conditions, including anxiety and mood disorders (Grade A). Stress management, yoga, massage, music therapy, energy conservation, and meditation are recommended for stress reduction, anxiety, depression, fatigue, and quality of life (Grade B). Many interventions (n = 32) had weaker evidence of benefit (Grade C). Some interventions (n = 7) were deemed unlikely to provide any benefit (Grade D). Notably, only one intervention, acetyl-l-carnitine for the prevention of taxane-induced neuropathy, was identified as likely harmful (Grade H) as it was found to increase neuropathy. The majority of intervention/modality combinations (n = 138) did not have sufficient evidence to form specific recommendations (Grade I). CONCLUSIONS Specific integrative therapies can be recommended as evidence-based supportive care options during breast cancer treatment. Most integrative therapies require further investigation via well-designed controlled trials with meaningful outcomes.