Background: Exertional breathlessness is a key symptom in cardiorespiratory disease and can be quantified using incremental exercise testing (IET), but its prognostic significance is unknown.  Research question: We evaluated the ability of abnormally high breathlessness intensity during IET to predict all-cause, respiratory, and cardiac mortality. Study Design and Methods: Longitudinal cohort study of adults referred for cycle IET followed prospectively for mortality assessed using the Swedish National Causes of Death Registry. Abnormally high exertional breathlessness was defined as a breathlessness intensity response (Borg 0-10 scale) > the upper limit of normal (ULN) using published reference equations. Mortality was analyzed using multivariable Cox regression, unadjusted and adjusted for age, sex, and body mass index. Results: Of the 13,506 people included (46% female, age 59±15 years), 2,867 (21%) had abnormally high breathlessness during IET. Over a median follow up of 8.0 years, 1,687 (12%) people died. No participant was lost to follow-up. Compared to those within normal predicted ranges, people with abnormally high exertional breathlessness had higher mortality from all causes (adjusted hazard ratio [aHR] 2.3, [95% confidence interval] 2.1-2.6), respiratory causes (aHR 5.2 [3.4-8.0]) and cardiac causes (aHR 3.0 [2.5-3.6]). Even among people with normal exercise capacity (defined as peak Watt >=75% of predicted exercise capacity, n=10,284) those with abnormally high exertional breathlessness were at greater risk of all-cause mortality than people with exertional breathlessness within the normal predicted range (aHR 1.5 [1.2-1.8]). Interpretation: Among people referred for cycle IET, abnormally high exertional breathlessness, quantified using healthy reference values, independently predicted all-cause, respiratory and cardiac mortality.

The authors have declared no competing interest.

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The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

Regional Ethical Review Board in Linköping

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As stated by Swedish Ethical Review Authority analysis (Dnr 2018/141-31 ) approving the analysis of this study the data is not allowed to be shared publicly. Sharing sensitive data such as health data publicly is not complying to article 9 of the General Data Protection Regulation (EU 2016/679) as this would compromise the privacy of the participants. The General Data Protection Regulation (EU 2016/679) also considers de-identified sensitive data as sufficient to risk the privacy of participants. According to Swedish law (2003:460) concerning research including humans, ethical permission is required to process data including humans. To access the data from the study, ethical approval first needs to be required from the Swedish Ethical Review Authority(https://etikprovningsmyndigheten.se). Researchers can then contact the corresponding author Viktor Elmberg (viktore@gmail.com) with suggestions for analysis.