Bisphosphonates and risk of atrial fibrillation: a meta-analysis

Denosumab vs. bisphosphonates in primary osteoporosis: a meta-analysis of comparative safety in randomized controlled trials

Denosumab and bisphosphonates for primary osteoporosis are generally well-tolerated, but their comparative safety remains unclear. We aimed to explore the comparative safety of denosumab and bisphosphonates in primary osteoporosis. Databases such as PubMed and Google Scholar were searched for relevant peer-reviewed randomized controlled trials published in English (as of December 2023). Trials comparing adverse events (AE) between denosumab and bisphosphonates in patients with primary osteoporosis were investigated. Data were pooled using a fixed- or random-effects model to determine the risk ratios (RR) and 95% confidence intervals (CIs) for various AEs in patients treated with denosumab in comparison to patients treated with bisphosphonates. Eleven trials (5,545 patients; follow-up period: 12-24 months) were included in this meta-analysis. All trials had a risk of bias (e.g., reporting bias linked to secondary endpoints and selection bias linked to random allocation). In comparison to bisphosphonates, denosumab was significantly associated with less withdrawal due to AEs (RR = 0.49; 95% CI 0.34-0.71), more five-point major adverse cardiovascular events (RR = 2.05; 95% CI 1.03-4.09), more cardiovascular AEs (RR = 1.61; 95% CI 1.07-2.41), more infections (RR = 1.14; 95% CI 1.02-1.27), more upper respiratory tract infections (RR = 1.56; 95% CI 1.08-2.25), less vertebral fractures (RR = 0.54; 95% CI 0.31-0.93), and less abdominal pain (RR = 0.44;95% CI 0.22-0.87). We explored the comparative safety of denosumab and bisphosphonates for primary osteoporosis, some of which could be attributed to their beneficial effects. However, all trials had a risk of bias. Further investigations are required to confirm our results.

Cardiovascular safety of zoledronic acid in the treatment of primary osteoporosis: A meta-analysis and systematic review

PURPOSE

Osteoporosis is intimately linked to cardiovascular disease and it has been uncertain that zoledronic acid is not correlated with cardiovascular disease. We intended to assess the cardiovascular safety of zoledronic acid in the treatment of primary osteoporosis.

METHODS

We included only randomized controlled trials (RCTs) of patients with osteoporosis receiving zoledronic acid or a placebo. We systematically searched PubMed, Embase, Web of Science, Cochrane CENTRAL, Scopus, the Chinese National Knowledge Infrastructure, ClinicalTrials.gov, and ICTRP from the time of database creation to April 5, 2023. Two investigators extracted data independently on study characteristics, outcomes of interest, and risk of bias based on PRISMA guidelines.

RESULTS

As of April 5, 2023, our search identified 32,361 records, and after excluding these records, 9 RCTs were included in the meta-analysis. The overall risk ratio for cardiovascular events with zoledronic acid for primary osteoporosis compared with placebo was 1.15 (95 % CI 1.05-1.26, I2=12 %, P = 0.002), while the risk of major adverse cardiovascular events with zoledronic acid (RR 1.03, 95 % CI 0. 89-1.18, I2=21 %, P = 0.71) was not significant, possibly due to atrial fibrillation (RR 1.21, 95 % CI 0.99-1.47, I2=0 %, P = 0.06) versus the increased relative risk of arrhythmia (RR 1.30, 95 % CI 1.11-1.52, I2=34 %, P = 0.001). Overall, the cardiovascular risk of zoledronic acid for the treatment of primary osteoporosis was not significant; however, the relative risk of elevated atrial fibrillation and arrhythmias remains to be further studied.

CONCLUSIONS

In women with primary osteoporosis, zoledronic acid may increase the risk of atrial fibrillation (P = 0.06) and arrhythmias (P = 0.001) compared with placebo, independent of the risk of major adverse cardiovascular events, angina, and heart failure. However, the sample size of men with primary osteoporosis is small, and the cardiovascular risk of zoledronic acid in men with osteoporosis is uncertain.

Antiosteoporosis medications and cardiovascular disease: a population-based nationwide nested case-control study

Purpose: Patients with osteoporosis are at an increased risk of cardiovascular disease (CVD). Several antiosteoporosis medications have been demonstrated with the benefit of preventing osteoporosis. Our aim is to assess the CVD risks associated with antiosteoporosis medications using the National Health Insurance Research Database in Taiwan between 2000 and 2016. Methods: Among 41,102 patients of 40+ years old with newly diagnosed osteoporosis, 69.1% (N = 28,387) of patients were included in the user cohort of antiosteoporosis medicines, of whom 13, 472 developed CVD by the end of 2016, while 14,915 did not. Using the nested case-control analysis in the user cohort (88.0% women and 77.4% elderly), we applied conditional logistic regression to estimate odds ratios (ORs) of eight types of CVD for the users of denosumab, bisphosphonate, teriparatide, and hormone replacement therapy (HRT). Results: The adjusted ORs of overall CVDs were 0.13 (95% CI: 0.12-0.15) for denosumab users, 0.52 (95% CI: 0.45-0.61) for teriparatide users, and 0.80 (95% CI: 0.76-0.85) for bisphosphonate users. The HRT users were at higher odds of coronary artery and peripheral artery diseases, heart failure, pulmonary embolism, and deep vein thrombosis. Conclusion: Denosumab, teriparatide, and bisphosphonate may have more protective effects against CVD than hormone therapy. Physicians may take subsequent cardiovascular risks into account when choosing an adequate antiosteoporosis medication for patients with osteoporosis.

The role of medications in successful aging

Successful aging includes good health and low levels of disability. To that end, primary prevention is far better than managing subsequent organ damage. When medication is needed to prevent or manage disease, the preferred choice should be associated with the greatest benefits and fewest adverse effects. Cardiovascular diseases are the leading cause of morbidity and mortality in postmenopausal women worldwide. Considering disease-adjusted life years, other leading causes are chronic obstructive pulmonary disease, diabetes mellitus, dementias, hearing loss, cancers of the breast, lung and bowel, osteoporosis, fractures and falls, depression, osteoarthritis, refractive errors of the eye and non-diabetic chronic kidney disease. This review explores the global prevalence of these diseases in women aged 50 years and older, and medications commonly used for them, and contrasts the effects of menopausal hormone therapy (MHT) with others. When initiated early, there is good evidence for MHT benefit in all-cause mortality and primary prevention of cardiovascular disease, diabetes and osteoporosis; fair evidence for benefit in dementias, depression and osteoarthritis; limited evidence for benefit in chronic obstructive pulmonary disease, hearing loss, non-diabetic chronic kidney disease and colorectal cancer; null effects on lung cancer and refractive errors; and varied effects on breast cancer and stroke. Relative benefits and adverse effects of other medications warrant consideration.

A Single-Center Prospective Study of 116 Women with Osteoporosis Treated with Zoledronic Acid Monitored by Electrocardiography for the Development of Cardiac Arrhythmia During the Acute Phase in China

Background

Concerns have been raised among clinicians and patients about the cardiovascular risks of bisphosphonates used in the treatment of osteoporosis. The goal of this study was to investigate the acute effect of zoledronic acid (ZA) infusion on arrhythmia development using an electrocardiograph (ECG).

Material/Methods

This prospective study was a self-controlled case series study that recruited 116 female patients with osteoporosis. The patients underwent standard 12-lead electrocardiography before and 1 day after zoledronic acid intravenous infusion to evaluate cardiac adverse effects and the change in ECG parameters after the infusion. Heart rhythm, atrial and ventricular premature contractions, atrial fibrillation, P wave, and QTc parameters were measured using an ECG. A blood biochemical examination was performed for all patients before the ZA infusion. Body temperature was measured twice per day.

Results

Before ZA administration, ECG findings were normal in 47 patients and abnormal in 69 patients. After ZA administration, ECG findings were normal in 35 patients and abnormal in 81 patients. New onsets of premature atrial contractions and atrial fibrillation were observed in 1 patient each, and new onsets of premature ventricular contractions were observed in 2 patients. The heart rate was obviously higher, and the QT interval was obviously shorter after ZA administration, compared with before administration. No significant differences in P wave and QTc parameters were found between the 2 ECG measurements.

Conclusions

During the acute phase, 116 women with osteoporosis who were treated with zoledronic acid infusion did not develop significantly abnormal ECG changes.

Risk of Incident Atrial Fibrillation With Zoledronic Acid Versus Denosumab: A Propensity Score-Matched Cohort Study

Zoledronic acid (ZA) is an effective agent in osteoporosis and malignancy-related bone disease but may be associated with increased risk of atrial fibrillation (AF), although current studies disagree on this risk. To examine the risk of incident AF among patients receiving ZA compared with denosumab in the first year of treatment, we performed a new-user, active comparator cohort study including privately insured Americans between January 1, 2010, and June 30, 2019. Individuals aged ≥50 years without known arrhythmia or advanced kidney disease who initiated ZA were 1:1 propensity score (PS)-matched to individuals initiating denosumab in separate osteoporosis and malignancy cohorts. The primary outcome was incident diagnosis of AF (≥1 inpatient or ≥2 outpatient diagnostic codes) over 1 year. Secondary outcomes included stroke/transient ischemic attack (TIA) and nonvertebral fracture. In the osteoporosis cohort (n = 16,235 pairs), mean age was 71 years, and 93% were female. There was higher risk of AF with ZA compared with denosumab over 1 year (incidence rate [IR] = 18.6 versus 14.9 per 1000 person-years; hazard ratio [HR] = 1.25; 95% confidence interval [CI] 1.04 to 1.50). In the malignancy cohort (n = 7732 pairs), mean age was 70 years, and 66% were female. There was a numerically higher, albeit not statistically significant, risk of AF with ZA compared with denosumab over 1 year (IR = 46.9 versus 39.0 per 1000 person-years; HR = 1.19; 95% CI 1.00 to 1.43; p = 0.06). No difference in stroke/TIA rates occurred. In the malignancy cohort, ZA was less effective than denosumab at preventing nonvertebral fractures (HR = 1.32; 95% CI 1.01 to 1.74). Compared with denosumab, ZA treatment for osteoporosis and possibly for malignancy-related bone disease is associated with modestly increased risk of incident AF in the first year of treatment. © 2020 American Society for Bone and Mineral Research (ASBMR).

The Belgian Bone Club 2020 guidelines for the management of osteoporosis in postmenopausal women

PURPOSE

To provide updated evidence-based guidelines for the management of osteoporosis in postmenopausal women in Belgium.

METHODS

The Belgian Bone Club (BBC) gathered a guideline developer group. Nine "Population, Intervention, Comparator, Outcome" (PICO) questions covering screening, diagnosis, non-pharmacological and pharmacological treatments, and monitoring were formulated. A systematic search of MEDLINE, the Cochrane Database of Systematic Reviews, and Scopus was performed to find network meta-analyses, meta-analyses, systematic reviews, guidelines, and recommendations from scientific societies published in the last 10 years. Manual searches were also performed. Summaries of evidence were provided, and recommendations were further validated by the BBC board members and other national scientific societies' experts.

RESULTS

Of the 3840 references in the search, 333 full texts were assessed for eligibility, and 129 met the inclusion criteria. Osteoporosis screening using clinical risk factors should be considered. Patients with a recent (<2 years) major osteoporotic fracture were considered at very high and imminent risk of future fracture. The combination of bone mineral density measured by dual-energy X-ray absorptiometry and 10-year fracture risk was used to categorize patients as low or high risk. Patient education, the combination of weight-bearing and resistance training, and optimal calcium intake and vitamin D status were recommended. Antiresorptive and anabolic osteoporosis treatment should be considered for patients at high and very high fracture risk, respectively. Follow-up should focus on compliance, and patient-tailored monitoring should be considered.

CONCLUSION

BBC guidelines and 25 guideline recommendations bridge the gap between research and clinical practice for the screening, diagnosis, and management of osteoporosis.

Environmental factors, serum biomarkers and risk of atrial fibrillation: an exposure-wide umbrella review of meta-analyses

Atrial fibrillation (AF) is the most common cardiac arrhythmia. We designed an umbrella review to systematically assess the epidemiological credibility of the associations of non-genetic factors with risk of AF. We searched PubMed and EMBASE from inception to December 31, 2018 to identify systematic reviews and meta-analyses of observational studies for the association of non-genetic factors with risk of AF. For each meta-analysis, we used the random-effects model, and we estimated the 95% confidence and prediction intervals. We also assessed between-study heterogeneity, small-study effects and excess significance bias. We identified 34 eligible papers that examined 51 associations of 42 unique non-genetic factors with risk of AF. Eighteen associations remained statistically significant at P value < 1 × 10^-6. Thirty-one associations presented large or very large between-study heterogeneity. Eight associations presented evidence for small-study effects and 13 associations had evidence for excess significance bias. Ten associations, i.e. corrected QT interval, alcohol consumption (highest vs. lowest category, per 1 drink/day increase), body mass index (> 30 units vs. < 30 units, per 5 units increase), waist circumference, body weight, type 2 diabetes mellitus, and smoking (ever vs. never, per 10 cigarettes/day increase) were supported by convincing or highly suggestive evidence in meta-analyses of prospective cohort studies. Type 2 diabetes mellitus, markers of adiposity, alcohol consumption, smoking, and corrected QT interval constitute credible risk factors of AF. Our proposed grading may guide the design of future studies, including Mendelian randomization studies, to assess whether these associations are causal.

Bisphosphonates and risk of cardiovascular events: a meta-analysis

Background and Objectives

Some evidence suggests that bisphosphonates may reduce atherosclerosis, while concerns have been raised about atrial fibrillation. We conducted a meta-analysis to determine the effects of bisphosphonates on total adverse cardiovascular (CV) events, atrial fibrillation, myocardial infarction (MI), stroke, and CV death in adults with or at risk for low bone mass.

Methods

A systematic search of MEDLINE and EMBASE through July 2014 identified 58 randomized controlled trials with longer than 6 months in duration that reported CV events. Absolute risks and the Mantel-Haenszel fixed-effects odds ratios (ORs) and 95% confidence intervals (CIs) of total CV events, atrial fibrillation, MI, stroke, and CV death were estimated. Subgroup analyses by follow-up duration, population characteristics, bisphosphonate types, and route were performed.

Results

Absolute risks over 25–36 months in bisphosphonate-treated versus control patients were 6.5% versus 6.2% for total CV events; 1.4% versus 1.5% for atrial fibrillation; 1.0% versus 1.2% for MI; 1.6% versus 1.9% for stroke; and 1.5% versus 1.4% for CV death. Bisphosphonate treatment up to 36 months did not have any significant effects on total CV events (14 trials; ORs [95% CI]: 0.98 [0.84–1.14]; I² = 0.0%), atrial fibrillation (41 trials; 1.08 [0.92–1.25]; I² = 0.0%), MI (10 trials; 0.96 [0.69–1.34]; I² = 0.0%), stroke (10 trials; 0.99 [0.82–1.19]; I² = 5.8%), and CV death (14 trials; 0.88 [0.72–1.07]; I² = 0.0%) with little between-study heterogeneity. The risk of atrial fibrillation appears to be modestly elevated for zoledronic acid (6 trials; 1.24 [0.96–1.61]; I² = 0.0%), not for oral bisphosphonates (26 trials; 1.02 [0.83–1.24]; I² = 0.0%). The CV effects did not vary by subgroups or study quality.

Conclusions

Bisphosphonates do not have beneficial or harmful effects on atherosclerotic CV events, but zoledronic acid may modestly increase the risk of atrial fibrillation. Given the large reduction in fractures with bisphosphonates, changes in osteoporosis treatment decision due to CV risk are not justified.

Atrial Fibrillation and Its Association with Endocrine Disorders

Atrial Fibrillation (AF) is the most common arrhythmia affecting millions of people and the number is rising, it is therefore important to understand the risk factors causing AF. Risk factors such as hypertension, heart failure, coronary heart disease, and type 2 diabetes mellitus increase the risk of AF, however, the underlying etiology in a majority of patients remains elusive. Many of the endocrine disorders have been implicated in causing AF and an in depth knowledge of these disorders helps in early diagnosis and treatment. Due to the high prevalence of AF and its complications, it is therefore important to recognize these risk factors and have a low threshold for suspicion while other common causes are being excluded. In this review we summarize the issues related to AF and endocrine disorders. A better understanding of the relationship may lead to the development of the primary preventive strategies, fostering a more preventive and predictive approach that may result in decreased incidence of AF and its associated complications and provide personalized treatment options. For this review we carried out a search of Pubmed, the words or combination of words we used for our search include Endocrine disorders, metabolic disorders, Dyslipidemia, Diabetes mellitus type 2, Vitamin D, Hyperthyroidism, Primary aldosteronism, Pheochromocytoma, Obesity, Hypercalcemia, Hypogonadism, Medications, and Atrial fibrillation. We also retrieved articles from the references of retrieved articles.

Clinical experience with intravenous zoledronic acid in the treatment of male osteoporosis: evidence and opinions

Osteoporosis frequently remains underrecognized and undertreated in men. Most osteoporosis-related fractures could be prevented if men at risk would be diagnosed, treated, and remained compliant with therapy. Bisphosphonates, the mainstay of osteoporosis treatment, are potent antiresorptive agents that inhibit osteoclast activity, suppress in vivo markers of bone turnover, increase bone mineral density, decrease fractures, and likely improve survival in men with osteoporosis. The focus of the article is on intravenous zoledronic acid, which may be a preferable alternative to oral bisphosphonate therapy in patients with cognitive dysfunction, the inability to sit upright, polypharmacy, significant gastrointestinal pathology or suspected medication noncompliance. Zoledronic acid is approved in the United States (US) and European Union (EU) as an annual 5 mg intravenous infusion to treat osteoporosis in men. The zoledronic acid 4 mg intravenous dose has been studied in the prevention of bone loss associated with androgen deprivation therapy. This article reviews the evidence for zoledronic acid, currently the most potent bisphosphonate available for clinical use, and its therapeutic effects in the treatment of men with osteoporosis.

Safety issues with bisphosphonate therapy for osteoporosis

Randomized controlled trials have demonstrated the efficacy of bisphosphonates (BP) in improving BMD and reducing fracture risk. Various safety issues that were not noted in clinical trials have, however, now emerged with post-marketing surveillance and increasing clinical experience. The risk of atypical femoral fracture could increase with long-term use of BP, although absolute risk is very small, particularly when balanced against benefits. A drug holiday should be considered after 5 years of treatment for patients at low risk of fracture, although there is no official recommendation regarding this to guide clinicians. Osteonecrosis of the jaw from low-dose BP used for osteoporosis is very rare, and mainly a complication with high-dose i.v. BP used in oncology. The risk of atrial fibrillation too is negligible, and a definite link cannot be established between BP and oesophageal cancer. BP should be avoided in patients with severe renal impairment and during pregnancy and lactation because of limited safety data. Further epidemiological and clinical data are required to establish safety of BP in long-term users (>5 years) and provide evidence-based management.

Drug-induced atrial fibrillation

Atrial fibrillation (AF) is a common cardiac arrhythmia that is associated with severe consequences, including symptoms, haemodynamic instability, increased cardiovascular mortality and stroke. While other arrhythmias such as torsades de pointes and sinus bradycardia are more typically thought of as drug induced, AF may also be precipitated by drug therapy, although ascribing causality to drug-associated AF is more difficult than with other drug-induced arrhythmias. Drug-induced AF is more likely to occur in patients with risk factors and co-morbidities that commonly co-exist with AF, such as advanced age, alcohol consumption, family history of AF, hypertension, thyroid dysfunction, sleep apnoea and heart disease. New-onset AF has been associated with cardiovascular drugs such as adenosine, dobutamine and milrinone. In addition, medications such as corticosteroids, ondansetron and antineoplastic agents such as paclitaxel, mitoxantrone and doxorubicin have been reported to induce AF. Whether bisphosphonate drugs are associated with new-onset AF remains controversial and requires further study. The potential contribution of specific drug therapy should be considered when patients present with new-onset AF.

Heart failure as a risk factor for osteoporosis and fractures

Although heart failure (HF) and osteoporosis are common diseases, particularly in elderly populations, patients with HF have an increased risk for osteoporosis. The relationship of HF with osteoporosis is modified by gender and the severity of HF. In addition, shared risk factors, medication use, and common pathogenic mechanisms affect both HF and osteoporosis. Shared risk factors for these 2 conditions include advanced age, hypovitaminosis D, renal disease, and diabetes mellitus. Medications used to treat HF, including spironolactone, thiazide diuretics, nitric oxide donors, and aspirin, may protect against osteoporosis. In contrast, loop diuretics may make osteoporosis worse. HF and osteoporosis appear to share common pathogenic mechanisms, including activation of the renin-angiotensin-aldosterone system, increased parathyroid hormone levels, and/or oxidative/nitrosative stress. HF is a major risk factor for mortality following fractures. Thus, in HF patients, it is important to carefully assess osteoporosis and take measures to reduce the risk of osteoporotic fractures.

Long-term treatment of osteoporosis in postmenopausal women: a review from the European Society for Clinical and Economic Aspects of Osteoporosis and Osteoarthritis (ESCEO) and the International Osteoporosis Foundation (IOF)

INTRODUCTION

Postmenopausal osteoporosis is a chronic disease requiring treatment that balances long-term fracture efficacy against risk.

METHODS

We reviewed the efficacy and safety of calcium and vitamin D, the selective estrogen receptor modulators (SERMs), the bisphosphonates, denosumab, and strontium ranelate in studies of 3 years or longer.

RESULTS

Six trials lasted for 5 years, and seven went beyond that. The evidence beyond 5 years is generally weak, mainly due to methodological issues (open-label design, small samples, or absence of placebo control). Although calcium and vitamin D appear to be beneficial, the data are insufficient to evaluate benefits and risk beyond 3 years. The fracture efficacy of SERMs beyond 5 years is not known, though increases in bone mineral density (BMD) appear to be maintained. The SERMs have good long-term safety, including protective effects against breast cancer. The bisphosphonates have established fracture efficacy to 3 years, and 4 or 5 years with alendronate and risedronate. The evidence beyond 5 years indicates sustained increases in BMD. The safety of the bisphosphonates does not appear to be modified with time, with the possible exceptions of atypical subtrochanteric fracture and other events of unknown frequency. Denosumab has been tested up to 5 years, with continued increased in BMD and no reported safety issues. There is evidence for fracture efficacy of strontium ranelate, and sustained increases in BMD over 10 years. Strontium ranelate has good long-term safety.

CONCLUSION

Robust long-term studies are relatively rare for the osteoporosis treatments, and generally show maintenance of BMD and, for some agents, an additional reduction in fracture incidence.

Clinical utility of clodronate in the prevention and management of osteoporosis in patients intolerant of oral bisphosphonates

Bisphosphonates have a long history in the treatment of osteoporosis and bone-related disease. This review focuses on the use of a specific nonaminobisphosphonate, clodronate, which appears to be much better tolerated than other bisphosphonates and free of high-risk contraindications. Specifically, this paper reviews its use in the prevention of osteoporosis in postmenopausal women, taking into account its tolerability profile and recent safety issues arising regarding the use of bisphosphonates.

Intravenous bisphosphonate therapy and atrial fibrillation/flutter risk in cancer patients: a nationwide cohort study

Background:

There is conflicting evidence regarding bisphosphonates and atrial fibrillation (AF) risk in osteoporosis patients. However, bisphosphonates are used in much higher doses in treatment of bone metastasis and hypercalcemia, but little is known about the AF risk in cancer patients.

Methods:

We conducted a nationwide population-based cohort study using Danish databases. All cancer patients exposed to intravenous bisphosphonates during 2000–2008 were matched with two non-exposed cancer patients by cancer type, distant metastasis presence at diagnosis, age, and gender. We used Cox proportional hazard regression to estimate hazards ratios (HRs) of AF/flutter adjusting for important confounding factors.

Results:

Of the 3981 cancer patients exposed to intravenous bisphosponates, 128 (3.2%) developed AF/flutter. This condition occurred in 192 (2.4%) of the 7906 non-exposed cancer patients, corresponding to an adjusted HR of 1.7 (95% CI: 1.2–2.4).

Conclusion:

Intravenous bisphosphonates may increase AF/flutter risk in cancer patients.

Bisphosphonates and esophageal cancer--a pathway through the confusion

Two recent papers that examined the association between oral bisphosphonates and the risk of esophageal cancer reported seemingly discrepant findings, despite both studies using data from the UK General Practice Research Database, from similar time periods. Each paper set out brief conclusions within their abstracts, generating two opposing impressions: that the risk of incident esophageal cancer is not significantly increased with bisphosphonate use, or that the risk is increased when bisphosphonates have been prescribed ten or more times, or for longer than 5 years. Of course, the latter conclusion was more widely reported in the popular press, and with patients arriving at the clinic wanting to discuss the reports, clinicians must be able to interpret the existing evidence correctly. In this article we discuss important methodological issues regarding the two observational studies, define areas of consensus and discrepancy, examine possible bias and confounding, and condense the results into a clinically useful summary.