https://orcid.org/0000-0001-8041-6994
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Andreas Ebbehoj, Per Løgstrup Poulsen, Esben Søndergaard, Incidence of PPGL according to altitude – Calendar time is of the essence, European Journal of Endocrinology, Volume 186, Issue 1, Jan 2022, Pages L1–L2, https://doi.org/10.1530/EJE-21-0680
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We recently read the article by Leung et al. (1) on the incidence of pheochromocytoma and paraganglioma (PPGL) with great enthusiasm. However, we have some concerns regarding the recent speculations on the relationship between the incidence of PPGL and the ‘modifiable’ risk factor of altitude in the correspondence between Patel and Mihai (2) and Leung et al. (3). In the first letter, Patel and Mihai laid out the evidence for the pseudo-hypoxia model as a cause of PPGL (4) and speculate on a possible association between altitude, hypoxia, and PPGL. In their reply, Leung et al. report the results of a meta-regression analysis to support the theory.
Unfortunately, Leung et al. do not provide any detail on how papers in their meta-regression were selected, while a number of other studies were not included (5, 6, 7, 8, 9, 10, 11). We therefore searched for all papers presenting the incidence of PPGL in a defined geographic location. We screened the identified references and included 14 relevant papers. Taking all these studies into account and collecting annual incidence rates rather than study averages, we redid the meta-regression analysis on the incidence of PPGL and altitude. The search strategy, study data, and code are available on https://github.com/andreasebbehoj/2021-EJE-letter-PPGL-altitude-and-time. In our analysis, altitude was still a predictor of PPGL incidence (Fig. 1A). However, the regression line fits the data poorly (R2 = 23.0%), and there is considerable heterogeneity between estimates (I2 = 93.8%). Therefore, a meta-regression of these heterogenous studies should be interpreted with caution.
