Objective: Exposure to high altitude may be a modifiable risk factor for pheochromocytoma and paraganglioma. The primary objective was to examine the association between the reported incidence of pheochromocytoma and paraganglioma across studies with differences in altitude.
Design: Meta-analysis with meta-regression.
Methods: The annual incidence proportion of pheochromocytoma and paraganglioma per 100,000 population was examined, accounting for differences in altitude. Meta-analysis using restricted maximum likelihood estimates with a random effects model was performed and meta-regression conducted to explore for heterogeneity.
Results: A total of 7 studies were identified from European, North American, and Asian countries. The pooled annual incidence proportion was 0.38 cases per 100,000 people (95% confidence interval [CI], 0.20 to 0.57 cases per 100,000 people) and this was associated with high amounts of statistical heterogeneity (P < 0.01; I2 = 97.5%). Meta-regression confirmed that altitude was significantly associated with the frequency of pheochromocytoma and paraganglioma. For every 500-meter increase in elevation, the annual incidence proportion increased by 0.31 cases per 100,000 people (95% CI, 0.01 to 0.61 cases per 100,000 people; P = 0.046). There were large amounts of residual statistical heterogeneity after meta-regression.
Conclusion: The incidence of pheochromocytoma and paraganglioma increased with altitude. However, variations between studies were only partially explained by elevation. Other factors, such as differences in study quality and the presence of clinical heterogeneity, likely impacted estimates of incidence.