Significant hearing loss due to prolonged stay in high altitude, finds Army study

Vijay Mohan

Tribune News Service

Chandigarh, November 7

Even as the unprecedented concentration of troops along the Himalayan border with China continues, a new study by military medical experts has highlighted the adverse impact on the hearing ability of soldiers who are deployed in high altitude areas over a prolonged period.

After observing significant variation in the threshold levels of hearing before and after induction in high altitude areas, the study has recommended greater focus on this area which has so far remained on the sidelines of research on the effects that high altitude has on the human body.

The hearing thresholds of 433 soldiers posted in high altitude areas were recorded using pure tone audiometry with different frequencies at the time of induction and then again after a year’s stay in high altitude.

Statistical comparison of the two sets of thresholds for air conduction revealed worsening of hearing in both ears, though there was some variation in the mean quantum of deterioration between right and left years. “These results are found to be statistically significant for all frequencies,” the study observed.

Titled, “A pilot study comparing hearing thresholds of soldiers at induction and after completion of one year in high altitude area,” the research undertaken by four military officers and an executive director in the Ministry of Health and Family Welfare, has been published in the latest issue of Medical Journal Armed Forces India.

“The pilot study shows deterioration of hearing thresholds in tested frequencies in both ears after a long stay (one year) in high altitude area,” the authors said. “We recommend further structured research on otologic effect of long term stay in high altitude,” they added.

The authors pointed out that despite so much research in high altitude area, our existing knowledge is still lacking on otological effects of long-term stay in high altitude. Otology is the branch of medicine dealing with the anatomy and physiology of the ear and its disorders and treatment.

This also assumes significance in light of another study jointly undertaken by western experts that was published in the International Archives of Occupational and Environmental Health in May 2021. The western study, while observing that temporary threshold shift for noise induced hearing loss is significantly more pronounced at high altitudes, said that acclimatisation does not provide any protection of the inner ear, although it increases arterial oxygen saturation.

High altitude is known to have adverse physiological as well as psychological impact on the human body due to extremely low temperature, lack of oxygen, dietary requirements, restricted movement and general isolation. All troops undergo a structured acclimatisation programme on induction into high altitude areas.

The Armed Forces Medical Services as well as the Defence Research and Development Organisation have undertaken voluminous research on high altitude deployment of men and equipment so as to mitigate the environmental impact on the human body and better sustain operations in the high snow-bound-mountains.