Longer apnea duration at low altitude in Tibetan and Han highlanders compared with Han lowlanders: A retrospective study

The Characteristics of Sleep Apnea in Tibetans and Han Long-Term High Altitude Residents

PURPOSE

Obstructive sleep apnea (OSA) is common both at low and high altitude. Since adaptations to high altitude and respiratory control may differ among Tibetans and Hans, we compared characteristics of sleep-disordered breathing in the two ethnic groups at high altitude.

MATERIALS AND METHODS

This was a prospective observational study including 86 Tibetan and Han long-term (>5 years) high altitude residents with chief complaints of snoring and/or witnessed apnea underwent clinical evaluation and polysomnography at 3200 meters in Shangri-La, China.

RESULTS

In 42 Tibetans, 38 men, median (quartiles) age was 50.0 (41.0; 56.0)y, total apnea/hypopnea index (AHI) 53.9 (32.0; 77.5)/h, obstructive AHI 51.0 (28.0; 72.2)/h and central AHI 1.5 (0.2; 3.1)/h. In 44 Hans, 32 men, median (quartiles) age was 47.0 (43.5; 51.0)y, total AHI 22.2 (12.8; 39.2)/h, obstructive AHI 17.7 (12.0; 33.0)/h and central AHI 2.4 (0.5; 3.4)/h (p < 0.001 total and obstructive AHI vs Tibetans). In Tibetans, mean nocturnal oxygen saturation was lower [median 85.0 (83.0; 88.0)% vs 88.5 (87.0; 90.0)%] and obstructive apnea and hypopnea duration was longer [22.0 (19.6; 24.8) sec vs 18.3 (16.7; 20.6) sec] than in Hans (all p < 0.001). In regression analysis, Tibetan ethnicity, neck circumference and high-altitude living duration were the predictors of total AHI. We also found that with every 10/h increase in total AHI, there were an approximately 0.9 beat/min and 0.8 beat/min increase in mean heart rate during rapid eye movement (REM) and non-REM sleep and 1.9 mmHg and 2.0 mmHg increase in evening and morning systolic blood pressure.

CONCLUSION

Our data suggest that Tibetans presented more severe obstructive sleep apnea, hypoxemia and longer apnea duration compared to Hans at 3200 meters, which was correlated with higher heart rate and blood pressure suggesting a greater cardiovascular risk.

Effect of One Night of Nocturnal Oxygen Supplementation on Highland Patients With OSA: A Randomized, Crossover Trial

BACKGROUND

The treatment of OSA in highland residents is not established.

RESEARCH QUESTIONS

Does nocturnal oxygen supplementation (NOS) improve sleep-related breathing disturbances, nocturnal oxygenation, and cognitive performance in patients with OSA living at 3,200 m?

STUDY DESIGN AND METHODS

Forty patients with OSA permanently living in Shangri-La, China at 3,200 m (median age [interquartile range], 47.0 [44.0-53.0] years; oxygen desaturation index, 38.4/h [34.2/h-52.3/h]), were randomly assigned to receive nasal NOS and sham oxygen (ambient air), for one night each, at 2 L/min, in a crossover design, separated by a washout period of 2 weeks. During treatment nights polysomnography was performed, and further outcomes were evaluated the next morning. The primary outcome was the difference in apnea-hypopnea index (AHI) between nights with NOS and nights with sham oxygen.

RESULTS

During nights with sham oxygen, the median (interquartile range) total AHI was 43.4/h (31.1/h-67.5/h), the obstructive AHI was 41.9/h (28.5/h-66.8/h), and the central AHI was 0.6/h (0.1/h-1.3/h); blood oxygenation as determined by pulse oximetry (Spo₂) was 87.0% (84.5%-89.0%). In intention-to-treat analysis, NOS decreased the total AHI by a median of 17.9/h (95% CI, 8.0/h-27.1/h; P < .001), through a reduction in obstructive AHI by 16.0/h (95% CI, 6.8/h-26.0/h; P < .001) and central AHI by 0.4/h (95% CI, 0.1/h-0.9/h; P < .001). NOS also increased Spo₂ by 7.0% (95% CI, 6.0%-8.0%; P < .001). Heart rate during sleep and pulse rate in the morning after NOS were significantly reduced, but subjective sleep quality and cognitive performance showed no changes.

INTERPRETATION

In highland residents with OSA, NOS significantly improved sleep-related breathing disturbances and nocturnal oxygenation. NOS also reduced heart rate during sleep and morning pulse rate. If these beneficial effects are confirmed in longer term studies, NOS may be a treatment option for highland patients with OSA who cannot be treated by CPAP.

TRIAL REGISTRY

Chinese Clinical Trial Registry; No.: ChiCTR1800017715; URL: http://www.chictr.org.cn/showproj.aspx?proj=29768.