Letter: Is Altitude-Induced Sleep Apnea Highly Dependent on Ethnic Background (Sherpa vs. Tamang)? We Are Not Convinced. (re: doi: 10.1089/ham.2022.0012)

Dear Editor,

We read with interest the recent article, “Altitude-Induced Sleep Apnea Is Highly Dependent on Ethnic Background (Sherpa vs. Tamang)” (Heiniger et al 2022). To evaluate the validity of the study, it is critical to know the details of the study subjects. These details are not adequately discussed in the article. We are also concerned that the study may not have been approved by the Nepal Health Research Council (NHRC), the organization by which all human subjects research in Nepal must be approved.

All subjects were male. We would like to know the rationale for choosing only male subjects. The ancestors of the subjects “had belonged to the same ethnic group for at least three generations. Ancestry information was verified via their identity documents.”

We would also like to know the specifics of the “identity documents” and the criteria for ethnicity of the subjects' ancestors. Many people in Nepal do not carry identity documents. Could the exclusion of female subjects and subjects without suitable identity documents or documents not meeting the criteria have introduced bias?

Subjects were excluded if they had “any known health condition potentially affecting nocturnal breathing.” Which conditions were exclusion criteria?

All subjects were smokers. Most Sherpas and Tamangs are nonsmokers. Smoking might affect apnea severity. The authors asked the subjects not to smoke for 24 hours before days on which they took measurements, but they do not report whether the subjects complied. Could the use of smokers only and the artificial condition of temporary smoking cessation, even if the subjects followed the recommendations, have introduced bias?

The authors do not mention the altitudes at which subjects were born and raised nor do they mention the altitudes of residence of the subjects. This could be an important source of bias, because control of breathing varies with these altitudes.

Most of the people living in the study area (Langtang) are Tamangs or Tibetan refugees. The Sherpa subjects, at least, would have had to be recruited elsewhere. Where were the subjects recruited? Were the subjects offered monetary or other incentives for participation?

The authors state that, “The study protocol was reviewed and accepted by the Nepalese Ethics Committee (number 730–2019).” We work in Nepal and are not aware of an institution called the Nepalese Ethics Committee. The NHRC accepted the authors' application (730-2019), but did the NHRC approve the study?

For studies by foreign researchers, the NHRC usually recommends that a Nepali health professional serve as a coprincipal investigator so that the foreign team members can receive adequate professional help to carry out the study in Nepal. The author list shows no such participation. Use of a local principal investigator would also help Nepal in terms of capacity building.

We respectfully request that the authors respond to our concerns.