Date Published: April 17, 2019
Publisher: Public Library of Science
Author(s): N. P. Sobers, N. Unwin, T. A. Samuels, S. Capewell, M. O’Flaherty, J. A. Critchley, Wisit Cheungpasitporn.
Although most countries face increasing population levels of obesity and diabetes their effect on coronary heart disease (CHD) mortality has not been often studied in small island developing states (SIDs) where obesity rates are among the highest in the world. We estimated the relative contributions of treatments and cardiovascular risk factors to the decline in CHD mortality from 1990 to 2012 in the Caribbean island, Barbados.
We used the IMPACT CHD mortality model to estimate the effect of increased coverage of effective medical/surgical treatments and changes in major CHD risk factors on mortality trends in 2012 compared with 1990. We calculated deaths prevented or postponed (DPPs) for each model risk factor and treatment group. We obtained data from WHO Mortality database, population denominators from the Barbados Statistical Service stratified by 10-year age group (ages 25–34 up to 85 plus), population-based risk factor surveys, Global Burden of Disease and Barbados’ national myocardial infarction registry. Monte Carlo probabilistic sensitivity analysis was performed.
In 1990 the age-standardized CHD mortality rate was 109.5 per 100,000 falling to 55.3 in 2012. Implementation of effective treatment accounted for 56% DPPs (95% (Uncertainty Interval (UI) 46%, 68%), mostly due to the introduction of treatments immediately after acute myocardial infarction (AMI) (14%) and unstable angina (14%). Overall, risk factors contributed 19% DPPs (95% UI 6% to 34%) mostly attributed to decline in cholesterol (18% DPPs, 95% UI 12%, 26%). Adverse trends in diabetes: 14% additional deaths(ADs) 95% UI 8% to 21% ADs) and BMI (2% ADs 95%UI 0 to 5% ADs) limited potential for risk factor gains.
Given the significant negative impact of obesity/diabetes on mortality in this analysis, research that explores factors affecting implementation of evidenced-based preventive strategies is needed. The fact that most of the decline in CHD mortality in Barbados was due to treatment provides an example for SIDs about the advantages of universal access to care and treatment.
Coronary heart disease (CHD) is the number one cause of death in the sub-region of the Americas known as the Caribbean. The Caribbean consists of 32 territories and small island developing states (SIDS), approximately half of which are classified as lower and/or middle income. Although most countries globally face increasing population levels of obesity, diabetes and non-communicable diseases (NCDs), rates in SIDs are among the highest in the world[2–4]. Many developed countries have been able to achieve decreases in CHD mortality over the past three to four decades. However, the picture is mixed among the nations of the Caribbean; countries such as St. Lucia, St. Vincent and Grenadines and Guyana have all recorded increases in age adjusted CHD mortality, while Barbados and Trinidad and Tobago have reported decreases over the period 1995 to 2008.
In 1990 the age-standardized CHD mortality rate was 109.5 per 100,000 per year, falling to 55.3 per 100,000 in 2012, a 46.1% decline in CHD deaths over this period (Table 1). This resulted in 139 fewer deaths being observed in 2012 compared with the expected number had the rates remained the same as in 1990. The model explained overall 75% (95% UI 59%, 96%) of deaths prevented or postponed (DPPs). Approximately 56%, 95% UI (46%, 68%) of these deaths were prevented because of the implementation of effective treatment for CHD while the best estimate from the model indicated that decline in risk factors prevented 19% additional deaths 95% UI (6%, 34%).
Using the IMPACT model for the small island developing state of Barbados, we found that 56% of the decline in CHD mortality was due to the introduction or improved uptakes of effective treatments while 19% was due to underlying change in risk factors. The highest percentages of DPPs were for treatments given in the first 24 hours for myocardial infarction and for treatment of hypertension and high cholesterol in primary care. Given the small size of the population the uncertainty intervals around our point estimates were wide; the lower and upper uncertainty intervals for the main model fit were 60% and 96% respectively and results must be interpreted accordingly.
We found that CHD mortality rates declined by approximately 46.1% in Barbados from 1990 to 2012. Approximately 56% of this decline can be attributed to the introduction and increased uptake of medical treatments, mostly drug therapies used in the first 24 hours after AMI as well as statins and anti-hypertensives prescribed in primary care. It is imperative that future research explores the feasibility and cost-effectiveness of introducing primary PCI as well as increasing uptake of medical treatments (including fibrinolysis) for CHD. Given the significant negative impact of obesity/diabetes on mortality in this analysis, research that explores factors affecting implementation of evidenced-based preventive strategies (e.g. increased physical activity, elimination of dietary trans-fats) to reduce diabetes and obesity is desperately needed. Exploring the reasons for these trends in other SIDs could facilitate quantifying the impact of universal access to care on CHD trends.