Persistent or developing dyspnea—a sensation of breathlessness—during daily activities reveals an increased risk of death, according to a study conducted by the universities of Jyväskylä and Helsinki. Dyspnea is normally used as an indicator of exercise intolerance and low fitness.
The prospective cohort study was conducted among all same-sex twin pairs born in Finland before 1958. It revealed that all-cause mortality increased along the degree of dyspnea during the 28-year follow-up, according to researchers.
In the study, twin individuals with persistent dyspnea (dyspnea noticed in 1975 and 1981) and dyspnea developers (dyspnea noticed in 1981) had an increased risk of death (hazard ratio [HR] 1.41, 95% CI 1.31-1.52 and 1.16, 1.05-1.25 respectively) compared to asymptomatic individuals. Easy shortness of breath also indicated an increased risk of death among individuals considered healthy at the 1981 baseline.
To eliminate genetic background effects, within-pair analyses were conducted among pairs that were discordant for dyspnea and mortality rate. These analyses showed an increased risk of death also among discordant pairs: twins with persistent dyspnea had an increased risk of death compared to their asymptomatic co-twins (HR 1.47, 1.23-1.77). Respectively, a risk difference was seen in the pairwise analysis among healthy monozygotic twin pairs discordant for dyspnea (HR 2.64, 95% CI 1.21-5.74).
Dyspnea was measured with a modified Medical Research Council (mMRC) scale. The scale includes four questions on the degree of dyspnea when walking and performing daily tasks. The level and change in dyspnea between 1975 and 1981 were used to predict mortality during a 28-year follow up (between 1981 and 2010). In total 21,379 twin individuals (including 8,672 complete twin pairs) were studied.
“Our study shows that persistent dyspnea (breathlessness) predicts increased mortality during a 28-year follow-up even among individuals without a clinically overt disease known to associate with dyspnea. Based on the results, we believe that the dyspnea score, which can be easily obtained and correlates with fitness outcomes, could be a screening tool for identifying unfit individuals at an increased mortality risk,” the researchers concluded.