Sustained Reduction in Cardiopulmonary Fitness in Long COVID

BACKGROUND: Long-term effect of COVID-19 (Long COVID) may persist for months or years after SARS-CoV-2 infection, but longer-term cardiopulmonary manifestations have not been previously reported. OBJECTIVES: The objective of the study was to characterize cardiopulmonary function after SARS-CoV-2 infection in a digital health substudy of the nationwide Researching COVID-19 to Enhance Recovery Adult Cohort Study. METHODS: Associations between wearable sensor device measures of cardiopulmonary fitness and survey-derived Long COVID symptoms were estimated over a 6-month window at least 6 months after infection using linear regression models adjusted for wear time, age, sex, race/ethnicity, and body mass index. RESULTS: Among 1,475 participants (72% female, 65% non-Hispanic White) a median of 21 months (IQR: 15-31 months) after infection, 498 (34%) had high symptom burden as characterized by the Researching COVID-19 to Enhance Recovery Long COVID Research Index (LCRI). High LCRI (vs low LCRI) was associated with significantly lower heart rate variability (-4.4 ms; 95% CI: -6.5 to -2.4; P < 0.001), higher resting heart rate (+1.5 beats/min [+0.7 to +2.4]; P < 0.001), fewer metabolic equivalent of task minutes (-96.3 [-128.8 to -63.8]; P < 0.001), lower step counts (-1,624 steps/day [-1,952 to -1,296]; P < 0.001), and lower activity levels (-7.9 minutes/day very or fairly active [-10.9 to -5.0]; P < 0.001). Hierarchal clustering analysis identified two subphenotypes with abnormal cardiovascular measures associated with low quality of life scores. CONCLUSIONS: Long COVID is associated with worse cardiovascular fitness. Additional studies are needed to determine if Long COVID is a novel risk factor for incident cardiovascular disease.