Stroke-Related Mortality at Different Altitudes: A 17-Year Nationwide Population-Based Analysis From Ecuador

Area of Science:

• Environmental Health
• Cardiovascular Epidemiology
• Altitude Medicine

Background:

• Over 5.7% of the global population lives above 1,500 meters, an environment associated with hypoxia.
• Hypothesis suggests acute hypoxia may increase stroke risk, but chronic exposure's effects remain debated, with some studies indicating reduced stroke incidence and mortality.
• Conflicting evidence necessitates further investigation into the relationship between altitude and stroke outcomes.

Purpose of the Study:

• To investigate the association between residential altitude and stroke hospital admissions and mortality rates.
• To analyze stroke epidemiology across distinct elevation ranges in Ecuador.
• To determine if higher altitudes confer a protective effect against stroke.

Main Methods:

• Ecological analysis of stroke hospital admissions and mortality data in Ecuador from 2001 to 2017.
• Population and cases categorized into four altitude groups: low (<1,500 m), moderate (1,500-2,500 m), high (2,500-3,500 m), and very high (3,500-5,500 m).
• Calculation of crude and direct standardized age-sex adjusted mortality and hospital admission rates.

Main Results:

• A total of 38,201 deaths and 75,893 stroke hospital admissions were analyzed.
• High altitude populations (HAP) exhibited significantly lower stroke mortality in both men (OR: 0.91) and women (OR: 0.83).
• HAP showed a reduced risk of hospital admission for stroke compared to low altitude residents: men (OR: 0.55) and women (OR: 0.65).

Conclusions:

• This study provides the first epidemiological evidence linking stroke outcomes to four distinct altitude ranges.
• Findings suggest living at higher elevations is associated with reduced stroke mortality and hospital admission probability.
• The protective effect of altitude on stroke appears most pronounced between 2,000 and 3,500 meters.