Background Single group data present unique challenges for synthesises of evidence. Proportional meta-analysis is becoming an increasingly common technique employed for the synthesis of single group data. Proportional meta-analysis shares many similarities with the conduct and reporting of comparative, or pairwise, meta-analysis. While robust and comprehensive methods exist detailing how researchers can conduct a meta-analysis that compares two (or more) groups against a common intervention, there is a scarcity of methodological guidance available to assist synthesisers of evidence in the conduct, interpretation, and importance of proportional meta-analysis in systematic reviews. Main body This paper presents an overview targeted to synthesisers of evidence and systematic review authors that details the methods, importance, and interpretation of a proportional meta-analysis. We provide worked examples of how proportional meta-analyses have been conducted in research syntheses previously and consider the methods, statistical considerations, and presentation of this technique. Conclusion This overview is designed to serve as practical guidance for synthesisers of evidence in the conduct of proportional meta-analyses.

The impact of non-communicable diseases (NCDs) in populations extends beyond ill-health and mortality with large financial consequences. To systematically review and meta-analyze studies evaluating the impact of NCDs (including coronary heart disease, stroke, type 2 diabetes mellitus, cancer (lung, colon, cervical and breast), chronic obstructive pulmonary disease and chronic kidney disease) at the macro-economic level: healthcare spending and national income. Medical databases (Medline, Embase and Google Scholar) up to November 6th 2014. For further identification of suitable studies, we searched reference lists of included studies and contacted experts in the field. We included randomized controlled trials, systematic reviews, cohorts, case-control, cross-sectional, modeling and ecological studies carried out in adults assessing the economic consequences of NCDs on healthcare spending and national income without language restrictions. All abstracts and full text selection was done by two independent reviewers. Any disagreements were resolved through consensus or consultation of a third reviewer. Data were extracted by two independent reviewers using a pre-designed data collection form. Studies evaluating the impact of at least one of the selected NCDs on at least one of the following outcome measures: healthcare expenditure, national income, hospital spending, gross domestic product (GDP), gross national product, net national income, adjusted national income, total costs, direct costs, indirect costs, inpatient costs, outpatient costs, per capita healthcare spending, aggregate economic outcome, capital loss in production levels in a country, economic growth, GDP per capita (per capita income), percentage change in GDP, intensive growth, extensive growth, employment, direct governmental expenditure and non-governmental expenditure. From 4,364 references, 153 studies met our inclusion criteria. Most of the studies were focused on healthcare related costs of NCDs. 30 studies reported the economic impact of NCDs on healthcare budgets and 13 on national income. Healthcare expenditure for cardiovascular disease (12-16.5 %) was the highest; other NCDs ranged between 0.7 and 7.4 %. NCD-related health costs vary across the countries, regions, and according to type of NCD. Additionally, there is an increase in costs with increased severity and years lived with the disease. Low- and middle-income (LMI) countries were the focus of just 16 papers, which suggests an information shortage concerning the true economic burden of NCDs in these countries. NCDs pose a significant financial burden on healthcare budgets and nations' welfare, which is likely to increase over time. However further work is required to standardize more consistently the methods available to assess the economic impact of NCDs and to involve (hitherto under-addressed) LMI populations across the globe.

Cardiovascular disease (CVD) risk factors, incidence and death increases from around the time of menopause comparing to women in reproductive age. A healthy lifestyle can prevent CVD, but it is unclear which lifestyle factors may help maintain and improve cardiovascular health for women after menopausal transition. We conducted a systematic review and meta-analysis of prospective cohort studies to evaluate the association between modifiable lifestyle factors (specifically smoking, physical activity, alcohol intake, and obesity), with CVD and mortality in middle-aged and elderly women. Pubmed, Embase, among other databases and reference lists were searched until February 29th, 2016. Study specific relative risks (RR) were meta-analyzed using random effect models. We included 59 studies involving 5,358,902 women. Comparing current versus never smokers, pooled RR were 3.12 (95% CI 2.15-4.52) for CHD incidence, 2.09 (95% CI 1.51-2.89) for stroke incidence, 2.76 (95% CI 1.62-4.71) for CVD mortality and 2.22 (95% CI 1.92-2.57) for all-cause mortality. Physical activity was associated with a decreased risk of 0.74 (95% CI 0.67-0.80) for overall CVD, 0.71 (95% CI 0.67-0.75) for CHD, 0.77 (95% CI 0.70-0.85) for stroke, 0.70 (95% CI 0.58-0.84) for CVD mortality and 0.71 (95% CI 0.65-0.78) for all-cause mortality. Comparing moderate drinkers versus non-drinkers, the RR was 0.72 (95% CI 0.56-0.91) for CHD, 0.63 (95% CI 0.57-0.71) for CVD mortality and 0.80 (95% CI 0.76-0.84) for all-cause mortality. For women with BMI 30-35 kg/m the risk was 1.67 (95% CI 1.24-2.25) for CHD and 2.3 (95% CI 1.56-3.40) for CVD mortality, compared to normal weight. Each 5 kg/m increase in BMI was associated with 24% (95% CI 16-33%) higher risk for all-cause mortality. This meta-analysis suggests that physical activity and moderate alcohol intake were associated with a reduced risk for CVD and mortality. Smoking and higher BMI were associated with an increased risk of these endpoints. Adherence to a healthy lifestyle may substantially lower the burden of CVD and reduce the risk of mortality among middle-aged and elderly women. However, this review highlights important gaps, as lack of standardized methods in assessing lifestyle factors and lack of accurate information on menopause status, which should be addressed by future studies in order to understand the role of menopause on the association between lifestyle factors and cardiovascular events.

Background: There is a notable lack of methodological and reporting guidance for systematic reviews of prevalence data. This information void has the potential to result in reviews that are inconsistent and inadequate to inform healthcare policy and decision making. The aim of this meta-epidemiological study is to describe the methodology of recently published prevalence systematic reviews. Methods: We searched MEDLINE (via PubMed) from February 2017 to February 2018 for systematic reviews of prevalence studies. We included systematic reviews assessing the prevalence of any clinical condition using patients as the unit of measurement and we summarized data related to reporting and methodology of the reviews. Results: A total of 235 systematic reviews of prevalence were analyzed. The median number of authors was 5 (interquartile range [IQR] 4-7), the median number of databases searched was 4 (3-6) and the median number of studies included in each review was 24 (IQR 15-41.5). Search strategies were presented for 68% of reviews. Forty five percent of reviews received external funding, and 24% did not provide funding information. Twenty three percent of included reviews had published or registered the systematic review protocol. Reporting guidelines were used in 72% of reviews. The quality of included studies was assessed in 80% of reviews. Nine reviews assessed the overall quality of evidence (4 using GRADE). Meta-analysis was conducted in 65% of reviews; 1% used Bayesian methods. Random effect meta-analysis was used in 94% of reviews; among them, 75% did not report the variance estimator used. Among the reviews with meta-analysis, 70% did not report how data was transformed; 59% percent conducted subgroup analysis, 38% conducted meta-regression and 2% estimated prediction interval; I 2 was estimated in 95% of analysis. Publication bias was examined in 48%. The most common software used was STATA (55%). Conclusions: Our results indicate that there are significant inconsistencies regarding how these reviews are conducted. Many of these differences arose in the assessment of methodological quality and the formal synthesis of comparable data. This variability indicates the need for clearer reporting standards and consensus on methodological guidance for systematic reviews of prevalence data.

The global economic impact of non-communicable diseases (NCDs) on household expenditures and poverty indicators remains less well understood. To conduct a systematic review and meta-analysis of the literature evaluating the global economic impact of six NCDs [including coronary heart disease, stroke, type 2 diabetes mellitus (DM), cancer (lung, colon, cervical and breast), chronic obstructive pulmonary disease (COPD) and chronic kidney disease (CKD)] on households and impoverishment. Medline, Embase and Google Scholar databases were searched from inception to November 6th 2014. To identify additional publications, reference lists of retrieved studies were searched. Randomized controlled trials, systematic reviews, cohorts, case-control, cross-sectional, modeling and ecological studies carried out in adults and assessing the economic consequences of NCDs on households and impoverishment. No language restrictions. All abstract and full text selection was done by two independent reviewers. Data were extracted by two independent reviewers and checked by a third independent reviewer. Studies were included evaluating the impact of at least one of the selected NCDs and on at least one of the following measures: expenditure on medication, transport, co-morbidities, out-of-pocket (OOP) payments or other indirect costs; impoverishment, poverty line and catastrophic spending; household or individual financial cost. From 3,241 references, 64 studies met the inclusion criteria, 75% of which originated from the Americas and Western Pacific WHO region. Breast cancer and DM were the most studied NCDs (42 in total); CKD and COPD were the least represented (five and three studies respectively). OOP payments and financial catastrophe, mostly defined as OOP exceeding a certain proportion of household income, were the most studied outcomes. OOP expenditure as a proportion of family income, ranged between 2 and 158% across the different NCDs and countries. Financial catastrophe due to the selected NCDs was seen in all countries and at all income levels, and occurred in 6-84% of the households depending on the chosen catastrophe threshold. In 16 low- and middle-income countries (LMIC), 6-11% of the total population would be impoverished at a 1.25 US dollar/day poverty line if they would have to purchase lowest price generic diabetes medication. NCDs impose a large and growing global impact on households and impoverishment, in all continents and levels of income. The true extent, however, remains difficult to determine due to the heterogeneity across existing studies in terms of populations studied, outcomes reported and measures employed. The impact that NCDs exert on households and impoverishment is likely to be underestimated since important economic domains, such as coping strategies and the inclusion of marginalized and vulnerable people who do not seek health care due to financial reasons, are overlooked in literature. Given the scarcity of information on specific regions, further research to estimate impact of NCDs on households ...