- Design
- Retrospective cohort, median 15-year follow-up
- Population
- 16,083 Norwegian adults referred with suspected sleep apnoea
- Primary outcome
- All-cause mortality
- Effect
- Third quartile of oesophageal pressure HR 1.21 (95% CI 1.03–1.43), adjusted
Between 2003 and 2016, 16,083 patients referred to a Norwegian service with suspected sleep apnoea had overnight polygraphy with oesophageal pressure monitoring, a direct measure of respiratory effort. Median age was 48, and they were followed for a median 15 years.
About 9% died. After adjustment for age, sex, BMI, comorbidities, apnoea-hypopnoea index and mean oxygen saturation, higher median respiratory effort remained associated with mortality (third quartile HR 1.21). The more time spent at high effort, the higher the risk.
The apnoea-hypopnoea index counts events but says little about how hard each breath is. Large negative intrathoracic pressures strain the heart and may explain risk the index misses.
Oesophageal pressure monitoring is invasive and rarely available. Surrogate effort signals from standard sleep studies are being developed, but this is not yet a routine measure.
- Look beyond the apnoea-hypopnoea index when judging sleep apnoea severity, including symptoms and oxygen desaturation.
- Treat patients with marked snoring and effortful breathing seriously even when event counts are modest.
- Watch for validated non-invasive effort measures in sleep study reports as they become available.
Why it matters
It challenges the reliance on a single event count to grade sleep apnoea.
Don't overread it
This was observational; it does not show that reducing effort lowers mortality.
The statistics, in plain English
A hazard ratio of 1.21 means about 21% higher risk of death over the follow-up, after accounting for other factors. The interval (1.03 to 1.43) is narrow at the lower end, so the true effect may be small.
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