The obesity paradox in heart failure patients with preserved versus reduced ejection fraction: a meta-analysis of individual patient data.

BACKGROUND: In heart failure (HF), obesity, defined as body mass index (BMI) ≥30 kg m(-2), is paradoxically associated with higher survival rates compared with normal-weight patients (the 'obesity paradox'). We sought to determine if the obesity paradox differed by HF subtype (reduced ejection fraction (HF-REF) versus preserved ejection fraction (HF-PEF)). PATIENTS AND METHODS: A sub-analysis of the MAGGIC meta-analysis of patient-level data from 14 HF studies was performed. Subjects were divided into five BMI groups: <22.5, 22.5-24.9 (referent), 25-29.9, 30-34.9 and ≥35 kg m(-2). Cox proportional hazards models adjusted for age, sex, aetiology (ischaemic or non-ischaemic), hypertension, diabetes and baseline blood pressure, stratified by study, were used to examine the independent association between BMI and 3-year total mortality. Analyses were conducted for the overall group and within HF-REF and HF-PEF groups. RESULTS: BMI data were available for 23 967 subjects (mean age, 66.8 years; 32% women; 46% NYHA Class II; 50% Class III) and 5609 (23%) died by 3 years. Obese patients were younger, more likely to receive cardiovascular (CV) drug treatment, and had higher comorbidity burdens. Compared with BMI levels between 22.5 and 24.9 kg m(-2), the adjusted relative hazards for 3-year mortality in subjects with HF-REF were: hazard ratios (HR)=1.31 (95% confidence interval=1.15-1.50) for BMI <22.5, 0.85 (0.76-0.96) for BMI 25.0-29.9, 0.64 (0.55-0.74) for BMI 30.0-34.9 and 0.95 (0.78-1.15) for BMI ≥35. Corresponding adjusted HRs for those with HF-PEF were: 1.12 (95% confidence interval=0.80-1.57) for BMI <22.5, 0.74 (0.56-0.97) for BMI 25.0-29.9, 0.64 (0.46-0.88) for BMI 30.0-34.9 and 0.71 (0.49-1.05) for BMI ≥35. CONCLUSIONS: In patients with chronic HF, the obesity paradox was present in both those with reduced and preserved ventricular systolic function. Mortality in both HF subtypes was U-shaped, with a nadir at 30.0-34.9 kg m(-2).

Systematic review and meta-analysis of the current evidence on the duration of protection by bacillus Calmette-Guérin vaccination against tuberculosis.

BACKGROUND: Recent evidence suggests that the duration of protection by bacillus Calmette-Guérin (BCG) may exceed previous estimates with potential implications for estimating clinical and cost-efficacy. OBJECTIVES: To estimate the protection and duration of protection provided by BCG vaccination against tuberculosis, explore how this protection changes with time since vaccination, and examine the reasons behind the variation in protection and the rate of waning of protection. DATA SOURCES: Electronic databases including MEDLINE, Excerpta Medica Database (EMBASE), Cochrane Databases, NHS Economic Evaluation Database (NHS EED), Database of Abstracts of Reviews of Effects (DARE), Web of Knowledge, Biosciences Information Service (BIOSIS), Latin American and Caribbean Health Sciences Literature (LILACs), MEDCARIB Database, Cumulative Index to Nursing and Allied Health Literature (CINAHL) were searched from inception to May 2009. Index to Theses, System for Information on Grey Literature in Europe (SIGLE), Centre for Agricultural Bioscience International (CABI) Abstracts, Scopus, Article First, Academic Complete, Africa-Wide Information, Google Scholar, Global Health, British National Bibliography for Report Literature, and clinical trial registration websites were searched from inception to October 2009. REVIEW METHODS: Electronic databases searches, screening of identified studies, data extraction and analysis were undertaken. Meta-analysis was used to present numerical and graphical summaries of clinical efficacy and efficacy by time since vaccination. Evidence of heterogeneity was assessed using the tau-squared statistic. Meta-regression allowed the investigation of observed heterogeneity. Factors investigated included BCG strain, latitude, stringency of pre-BCG vaccination tuberculin testing, age at vaccination, site of disease, study design and vulnerability to biases. Rate of waning of protection was estimated using the ratio of the measure of efficacy after 10 years compared with the efficacy in the first 10 years of a study. RESULTS: Study selection. A total of 21,030 references were identified, providing data on 132 studies after abstract and full-text review. Efficacy. Protection against pulmonary tuberculosis in adults is variable, ranging from substantial protection in the UK MRC trial {rate ratio 0.22 [95% confidence interval (CI) 0.16 to 0.31]}, to absence of clinically important benefit, as in the large Chingleput trial [rate ratio 1.05 (95% CI 0.88 to 1.25)] and greater in latitudes further away from the equator. BCG vaccination efficacy was usually high, and varied little by form of disease (with higher protection against meningeal and miliary tuberculosis) or study design when BCG vaccination was given only to infants or to children after strict screening for tuberculin sensitivity. High levels of protection against death were observed from both trials and observational studies. The observed protective effect of BCG vaccination did not differ by the strain of BCG vaccine used in trials. DURATION: Reviewed studies showed that BCG vaccination protects against pulmonary and extrapulmonary tuberculosis for up to 10 years. Most studies either did not follow up participants for long enough or had very few cases after 15 years. This should not be taken to indicate an absence of effect: five studies (one trial and four observational studies) provided evidence of measurable protection at least 15 years after vaccination. Efficacy declined with time. The rate of decline was variable, with faster decline in latitudes further from the equator and in situations where BCG vaccination was given to tuberculin-sensitive participants after stringent tuberculin testing. LIMITATIONS: The main limitation of this review relates to quality of included trials, most of which were conducted before current standards for reporting were formulated. In addition, data were lacking in some areas and the review had to rely on evidence from observational studies. CONCLUSIONS: BCG vaccination protection against tuberculosis varies between populations, to an extent that cannot be attributed to chance alone. Failure to exclude those already sensitised to mycobacteria and study latitude closer to the equator were associated with lower efficacy. These factors explained most of the observed variation. There is good evidence that BCG vaccination protection declines with time and that protection can last for up to 10 years. Data on protection beyond 15 years are limited; however, a small number of trials and observational studies suggest that BCG vaccination may protect for longer. Further studies are required to investigate the duration of protection by BCG vaccination. FUNDING: The National Institute for Health Research Health Technology Assessment programme.