BackgroundGrowing levels of both obesity and chronic disease in the general population pose a major public health problem. In the UK, an innovative 'health and weight' cohort trials facility, the 'South Yorkshire Cohort', is being built in order to provide robust evidence to inform policy, commissioning and clinical decisions in this field. This protocol reports the design of the facility and outlines the recruitment phase methods.Method/DesignThe South Yorkshire Cohort health and weight study uses the cohort multiple randomised controlled trial design. This design recruits a large observational cohort of patients with the condition(s) of interest which then provides a facility for multiple randomised controlled trials (with large representative samples of participants, long term outcomes as standard, increased comparability between each trial conducted within the cohort and increased efficiency particularly for trials of expensive interventions) as well as ongoing information as to the natural history of the condition and treatment as usual.This study aims to recruit 20,000 participants to the population based South Yorkshire Cohort health and weight research trials facility. Participants are recruited by invitation letters from their General Practitioners. Data is collected using postal and/or online patient self completed Health Questionnaires. NHS numbers will be used to facilitate record linkage and access to routine data. Participants are eligible if they are: aged 16 - 85 years, registered with one of 40 practices in South Yorkshire, provide consent for further contact from the researchers and to have their information used to look at the benefit of health treatments. The first wave of data is being collected during 2010/12 and further waves are planned at 2 - 5 year intervals for the planned 20 year duration of the facility.DiscussionThe South Yorkshire Cohort combines the strengths of the standard observational, longitudinal cohort study design with a population based cohort facility for multiple randomised controlled trials in a range of long term health and weight related conditions (including obesity). This infrastructure will allow the rapid and cheap identification and recruitment of patients, and facilitate the provision of robust evidence to inform the management and self-management of health and weight.
Summary Objectives To re-assess the quality of the epidemiological studies used to estimate the global burden of depression 2000, as published in the GBDep study. Design Primary and secondary data sources used in the global burden of depression estimate were identified and assigned to country of origin. Each source was assessed with respect to completeness and representativeness for national/regional estimates and against the inclusion criteria used by the scientific team estimating GBDep. Setting Not applicable. Participants Not applicable. Main outcome measures Not applicable. Results First, National estimates: The 28 scientific sources cited in the GBDep study related to 40 of the 191 WHO member countries. The EURO region had studies relating to 15 of 52 countries whereas AFRO region had studies for only three of 46 countries. Only six of the 40 countries had data drawn from a nationally representative population: the three AFRO country studies were based on a single village or town and, likewise, SEARO region had no nationally representative data; second, GBDep criteria: GBDep inclusion criteria required study sample size of more than 1000 people; 19 (45%) of the 42 studies did not meet this criterion. Sixteen (44%) of 36 studies did not meet the requirement that studies show a clear sample frame and method. GBD estimates rely on estimates of incidence; only two of the 42 country studies provided incidence data (Canada and Norway), the remaining 34 studies were prevalence studies. Duration of depression is based on three studies conducted in the USA and Holland. Conclusions Most studies exhibit significant shortcomings and limitations with respect to study design and analysis and compliance with GBDep inclusion criteria. Poor quality data limit the interpretation and validity of global burden of depression estimates. The uncritical application of these estimates to international healthcare policy-making could divert scarce resources from other public healthcare priorities.
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