Background Despite numerous studies and meta-analyses the prognostic effect of cardiac rehabilitation is still under debate. This update of the Cardiac Rehabilitation Outcome Study (CROS II) provides a contemporary and practice focused approach including only cardiac rehabilitation interventions based on published standards and core components to evaluate cardiac rehabilitation delivery and effectiveness in improving patient prognosis. Design A systematic review and meta-analysis. Methods Randomised controlled trials and retrospective and prospective controlled cohort studies evaluating patients after acute coronary syndrome, coronary artery bypass grafting or mixed populations with coronary artery disease published until September 2018 were included. Results Based on CROS inclusion criteria out of 7096 abstracts six additional studies including 8671 patients were identified (two randomised controlled trials, two retrospective controlled cohort studies, two prospective controlled cohort studies). In total, 31 studies including 228,337 patients were available for this meta-analysis (three randomised controlled trials, nine prospective controlled cohort studies, 19 retrospective controlled cohort studies; 50,653 patients after acute coronary syndrome 14,583, after coronary artery bypass grafting 163,101, mixed coronary artery disease populations; follow-up periods ranging from 9 months to 14 years). Heterogeneity in design, cardiac rehabilitation delivery, biometrical assessment and potential confounders was considerable. Controlled cohort studies showed a significantly reduced total mortality (primary endpoint) after cardiac rehabilitation participation in patients after acute coronary syndrome (prospective controlled cohort studies: hazard ratio (HR) 0.37, 95% confidence interval (CI) 0.20–0.69; retrospective controlled cohort studies HR 0.64, 95% CI 0.53–0.76; prospective controlled cohort studies odds ratio 0.20, 95% CI 0.08–0.48), but the single randomised controlled trial fulfilling the CROS inclusion criteria showed neutral results. Cardiac rehabilitation participation was also associated with reduced total mortality in patients after coronary artery bypass grafting (retrospective controlled cohort studies HR 0.62, 95% CI 0.54–0.70, one single randomised controlled trial without fatal events), and in mixed coronary artery disease populations (retrospective controlled cohort studies HR 0.52, 95% CI 0.36–0.77; two out of 10 controlled cohort studies with neutral results). Conclusion CROS II confirms the effectiveness of cardiac rehabilitation participation after acute coronary syndrome and after coronary artery bypass grafting in actual clinical practice by reducing total mortality under the conditions of current evidence-based coronary artery disease treatment. The data of CROS II, however, underscore the urgent need to define internationally accepted minimal standards for cardiac rehabilitation delivery as well as for scientific evaluation.

Decreased oxygen availability at high altitude requires physiological adjustments allowing for adequate tissue oxygenation. One such mechanism is a slow increase in the hemoglobin concentration ([Hb]) resulting in elevated [Hb] in high-altitude residents. Diagnosis of anemia at different altitudes requires reference values for [Hb]. Our aim was to establish such values based on published data of residents living at different altitudes by applying meta-analysis and multiple regressions. Results show that [Hb]is increased in all high-altitude residents. However, the magnitude of increase varies among the regions analyzed and among ethnic groups within a region. The highest increase was found in residents of the Andes (1 g/dL/1000 m), but this increment was smaller in all other regions of the world (0.6 g/dL/1000 m). While sufficient data exist for adult males and females showing that sex differences in [Hb] persist with altitude, data for infants, children, and pregnant women are incomplete preventing such analyses. Because WHO reference values were originally based on [Hb] of South American people, we conclude that individual reference values have to be defined for ethnic groups to reliably diagnose anemia and erythrocytosis in high-altitude residents. Future studies need to test their applicability for children of different ages and pregnant women.

Background Exercise-based cardiac rehabilitation (ebCR) often includes various psychological interventions for lifestyle change or distress management. However, the additional benefit of specific psychological interventions on depression, anxiety, quality of life, cardiac morbidity and cardiovascular or total mortality is not well investigated. Design Systematic review and meta-analysis. Methods Randomized controlled trials and controlled cohort trials published between January 1995 and October 2017 comparing ebCR with or without pre-specified psychosocial interventions were selected and evaluated on the basis of predefined inclusion and outcome criteria. Results Out of 15,373 records, 20 studies were identified, including 4450 patients with coronary artery disease (88.5%) or congestive heart failure (11.5%), respectively. Studies were of low to moderate quality and methodological heterogeneity was high. As compared with ebCR alone, additional psychological interventions for lifestyle change or distress management showed a trend to reduce depressive symptoms (standardized mean difference –0.13, 95% confidence interval (CI) –0.30; 0.05). Furthermore, during a follow-up of five years, distress management was associated with a trend to reduce cardiac morbidity (risk ratio 0.74, 95% CI 0.51; 1.07). There was no evidence for an additional impact of either psychological lifestyle change interventions or distress management on anxiety, quality of life, cardiovascular or total mortality. Conclusions Specific psychological interventions offered during ebCR may contribute to a reduction of depressive symptoms and cardiac morbidity, but there remains considerable uncertainty under which conditions these interventions exert their optimal effects. (CRD42015025920).