Epidemiological characterization of ischemic heart disease at different altitudes: A nationwide population-based analysis from 2011 to 2021 in Ecuador

Abstract

Background Cardiovascular diseases, including ischemic heart disease, are the leading cause of premature death and disability worldwide. While traditional risk factors such as smoking, obesity, and diabetes have been thoroughly investigated, non-traditional risk factors like high-altitude exposure remain underexplored. This study aims to examine the incidence and mortality rates of ischemic heart disease over the past decade in Ecuador, a country with a diverse altitude profile spanning from 0 to 4,300 meters. Methods We conducted a geographic distribution analysis of ischemic heart disease in Ecuador, utilizing hospital discharge and mortality data from the National Institute of Census and Statistics for the years 2011–2021. Altitude exposure was categorized according to two distinct classifications: the traditional division into low (< 2,500 m) and high (> 2,500 m) altitudes, as well as the classification proposed by the International Society of Mountain Medicine, which delineates low (< 1,500 m), moderate (1,500–2,500 m), high (2,500–3,500 m), and very high (3,500–5,800 m) altitudes. Findings From 2011–2021, we analyzed 49,765 IHD-related hospital admissions and 62,620 deaths. Men had an age-adjusted incidence rate of 55.08/100,000 and a mortality rate of 47.2/100,000, compared to 20.77/100,000 and 34.8/100,000 in women. Incidence and mortality surged in 2020 by 83% in men and 75% in women. Altitudinal stratification revealed higher IHD rates at lower altitudes (<2500 m), averaging 61.65 and 121.8 per 100,000 for incidence and mortality, which declined to 25.9 and 38.5 at elevations >2500 m. Men had more pronounced rates across altitudes, exhibiting 138.7% and 150.0% higher incidence at low and high altitudes respectively, and mortality rates increased by 48.3% at low altitudes and 23.2% at high altitudes relative to women. Conclusion Ecuador bears a significant burden of ischemic heart disease (IHD), with men being more affected than women in terms of incidence. However, women have a higher percentage of mortality post-hospital admission. Regarding elevation, our analysis, using two different altitude cutoff points, reveals higher mortality rates in low-altitude regions compared to high-altitude areas, suggesting a potential protective effect of high elevation on IHD risk. Nevertheless, a definitive dose-response relationship between high altitude and reduced IHD risk could not be conclusively established.

Work at high altitude and non-fatal cardiovascular disease associated with unfitness to work: Prospective cohort observation

“…There is no consensus in the results of these studies. Thus, when hospital admissions and mortality in the high-altitude locations of Ecuador were compared to low altitude, high altitude yielded protective effect [ 20 ], but when patients with heart failure were considered, high altitude increased the risk of adverse events [ 36 ]. Furthermore, the largest published cohort of workers exposed to high altitude during the high-altitude railroad construction [ 30 ] could not clarify the risks for workers with CAD, because the diagnosis was a contraindication to work and subjects were not allowed to ascend to the worksite.…”

“…Even more research efforts have been put to characterize cardiovascular adaptation and the risk at high altitude. Earlier studies in Central Asia and more recent studies in Ecuador have shown low cardiovascular risk in the highlanders [ 4 – 6 , 20 ]. At present, epidemiological evidence on cardiovascular disease (CVD) at high altitude is conflicting [ 16 ], when lower ischemic heart disease burden in some studies [ 20 ] may be higher in the other [ 21 ].…”

“…Earlier studies in Central Asia and more recent studies in Ecuador have shown low cardiovascular risk in the highlanders [ 4 – 6 , 20 ]. At present, epidemiological evidence on cardiovascular disease (CVD) at high altitude is conflicting [ 16 ], when lower ischemic heart disease burden in some studies [ 20 ] may be higher in the other [ 21 ]. Discrepancies pertain to arterial hypertension and diabetes, but mortality from CVD has been consistently lower at high altitude [ 16 , 20 ].…”