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The Evidence Speaks (September 2017)

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The Evidence Speaks Series is a recurring feature highlighting the latest in CHÉOS research. This series features summaries of select publications as well as in-depth features on the latest work from our investigators.

In the early days of CHÉOS, the Centre had a series known as “The Evidence Speaks,” a monograph series to keep media and the research community up-to-date with CHÉOS’ current research results in the health outcomes field.

Ke CH, Morgan S, Smolina K, Gasevic D, Qian H, Khan NA. Is cardiovascular risk reduction therapy effective in South Asian, Chinese and other patients with diabetes? A population-based cohort study from Canada. BMJ Open. 2017 Aug 31;7(8):e013808.

People of South Asian (originating from Pakistan, India, or Bangladesh) and Chinese ethnicity (originating from China, Taiwan or Hong Kong) represent over 60 per cent of adults with type 2 diabetes in the world. Although the pharmacological treatment of hypertension in diabetic individuals significantly reduces mortality, the evidence for the use these medications comes from trials predominantly in people of European descent. Furthermore, research has shown the benefits and side effects of different cardiovascular risk reduction therapies can vary depending on ethnicity. To improve this knowledge gap, CHÉOS Scientist Dr. Nadia Khan led a population-based cohort study of adults living in B.C. with newly diagnosed diabetes. Via Population Data BC, administrative data of over 200,000 individuals were included in the analysis; ethnicity was determined using surname and participants were classified as either treated or untreated with each class of antihypertensive medication: angiotensin receptor blockers (ARB), ACE inhibitors (ACEi), calcium channel blockers (CCB), and diuretics. In Chinese participants, mortality reduction was seen with ARB, diuretics, and, to a less significant extent, ACEi. No benefit of CCB was seen. For South Asians, none of the drug classes showed significant association with mortality or reduction of cardiovascular risk. Although the observed lack of effectiveness was most likely a result of poor medication adherence and a relatively low-risk study population, the results highlight the potential disparity in medication responses between ethnicities. Ethnically diverse clinical trials are imperative to understanding the true effect of these types of medications at a population level.

McCracken R, McCormack J, McGregor MJ, Wong ST, Garrison S. Associations between polypharmacy and treatment intensity for hypertension and diabetes: a cross-sectional study of nursing home patients in British Columbia, Canada. BMJ Open. 2017 Aug 11;7(8):e017430.

The potentially harmful over-prescription of multiple medical interventions, known as polypharmacy, may be associated with adverse events in elderly individuals. As part of her PhD at the University of British Columbia, CHÉOS’ Dr. Rita McCracken led a study to describe the prevalence and potential implications of polypharmacy in nursing home residents treated for diabetes and hypertension. The charts of over 200 nursing home residents in Vancouver, residing at six homes, were sampled. Overtreatment of diabetes and hypertension were defined using thresholds for glycosylated hemoglobin (HbA1c ≤7.5%) and systolic blood pressure (SBP ≤128 mmHg, ≥1 anti-hypertensive), respectively. A general measure of polypharmacy was calculated by subtracting the number of condition-specific medications from the total number of prescribed medications. Results showed that 54 per cent of treated diabetics had an HbA1c ≤7.5% and 44 per cent of treated hypertensives had an SBP ≤128. The study also showed that polypharmacy was associated with a greater, and potentially excessive, lowering of these surrogate measures. The majority of study participants were categorized as severely frail; the study authors suggest that frailty-specific guidelines for defining overtreatment may be necessary in this population and that reduction in treatment-specific medications could help to reduce harmful overtreatment and polypharmacy.

Tonelli M, Wiebe N, Bello A, Field CJ, Gill JS, Hemmelgarn BR, Holmes DT, Jindal K, Klarenbach SW, Manns BJ, Thadhani R, Kinniburgh D; Alberta Kidney Disease Network. Concentrations of trace elements in hemodialysis patients: A prospective cohort study. Am J Kidney Dis. 2017 Aug 22 [epub ahead of print].

Patients who are undergoing hemodialysis can inadvertently have toxic trace elements introduced to their bodies or, conversely, have biologically essential trace elements removed. Although the accumulation or depletion of some trace elements can be clinically significant, the concentrations of these substances in the body are rarely measured. To identify the prevalence of potentially harmful concentrations of trace elements, CHÉOS’ Dr. John Gill, along with researchers from the Universities of Calgary and Alberta, conducted a prospective longitudinal study of hemodialysis patients. Participating patients enrolled in renal programs in Alberta and B.C. were followed for up to two years following initiation of hemodialysis; twenty-five trace elements were measured. Based on previous data, study investigators anticipated that low concentrations of zinc, selenium, and manganese would be found; laboratory analysis found no evidence of deficiency of these three elements. The proportion of patients with plasma concentrations above the 95th percentile for arsenic remained relatively constant (9.1–9.8%). The prevalence of high concentrations of plasma mercury varied between 15.2% and 29.3%. Nearly all of patients participating in the analysis were found to have excessive levels of plasma lead. The clinical implications of low or high plasma concentrations of these trace elements, particularly those that were unexpected (e.g. tungsten, nickel, chromium), are unclear. However, this analysis can provide direction for future observational and interventional studies in hemodialysis patients.

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