Of the enrolled 39 patients with COVID-19 in January 2020, 1 patients (2.5%) deviated from Nanchong. Among the 38 survivors, 5 patients (10.5%) were lost to follow-up at the 12-month assessment. Thus, there were only 33 patients (87.2%), 15 Females (45.5%), 18 Males (54.5%), who had completed the three assessments; the mean age of the 33 patients was 40.8 ± 13.8 years, body mass index(BMI) was 22.7 ± 1.3 kg/m2). The hospital length of stay (LOS) for the group was 19.6 ± 6.6 day). Three patients were smokers (9.1%), 6 patients had medical comorbidity (1 chronic obstructive pulmoriary disease (COPD), 1 tuberculosis, 1 Cardiomegaly, 3 hypertension). All patients were diagnosed with mild COVID-19, with fever, cough, fatigue, muscle soreness, and sore throat as the main symptoms.
Pulmonary Function Tests
The results of pulmonary function tests are shown in Table 1. Generally, lung volume parameters and ventilatory function were well preserved at 3, 6 and 12 months. At 3 months, 9/33 (27.2%) of survivors had a FVC < 80% of the predicted value, 18/33 (66.7%) of survivors had a FEV1 < 80% of the predicted value. the proportion of patients with FEF25, FEF50, FEF75, and MMEF < 70% values were 51.5%, 21.2%, 15.2%, and 39.4%
At 6 months, 7/33(21.2%) of patients had a FVC < 80% of the predicted value, 16/33 (48.5%) of survivors had a FEV1 < 80% of the predicted value. the proportion of patients with FEF25, FEF50, FEF75, and MMEF < 70% values were 15/33(45.5%), 6/33༈18.2%༉, 3/33༈9.1%༉, and 9/33༈27.3%༉, respectively.
At 12 months, 6/33(18.2%)of patients had a FVC < 80% of the predicted value, 36.4% of patients had a FEV1 < 80% of the predicted value. The proportion of patients with FEF25, FEF50, and FEF75 < 70% values were 9/33༈27.3%༉, 3/33༈9.1%༉, and 2/33༈6.1%༉, respectively. Thus, there were 23 patients (23.7%) with impaired MMEF, whereas 9% of patients showed a reduction in FEV1/FVC at 12 months.
The mean 6MWD values in COVID-19 survivors increased significantly from 397 ± 25.4 m at 3 months to 514 ± 40.8 m) at 12 months (Table 3). When subjects were stratified into different age groups, they generally had significantly lower physical capacity than corresponding normal groups of historical normative database. The comparison of the 6MWD of COVID-19 survivors at 3, 6 and 12 months with that of historical normative data is shown in Table 2.
Univariate and multivariate analyses were performed to investigate the factors associated with 6MWD, with the control for sex (Table 3). The percentage of predicted FVC, FEV1, MEF25, and MMEF, and the LOS were positive independent predictors of 6MWD at 3-month post-discharge. The percentages of predicted FVC, FEV1, and MMEF were significant as the positive independent predictors of 6MWD at 6 months post-discharge. The percentage of predicted FVC and FEV1 were independent positive predictors of 6MWD the at 12 months post-discharge.
26/33 (78.8%, F/M: 45.5%/33.3%) of Covid-19 survivors had anxiety symptoms at 3 months, 21/33(63.6%)survivors (Female: 30.3%, Male:33.3%) at 6 months, and 42.4% survivors (Female: 21.2%, Male:21.2%) at 12 months. While, the percentage of subjects with depressive symptoms was 81.8% (Female:42.4%, Male: 39.4%), 66.7% (Female:36.4%, Male: 30.3%), 45.5% (Female:24.2%, Male: 21.2%), respectively. The mean scores of SDS and SAS showed decreasing trends from 3 months to 12 months post-discharge (Table 4).
Health Status of COVID-19 Survivors and Its Correlation with other Factors
Correlations between pulmonary function parameters, 6MWD, mental health and SF-36 domains at 12 months are shown in Table 5. There was a significant correlation between FEV1 with the two domains of SF-36 (PF and VT) (r = 0.525, p = 0.000; r = 0.483, p = 0.018), and between FEF25 and VT (r = 0.524, p = 0.001). 6MWD was significantly correlated with 4 domains (PF, BP, VT, and RE) of SF-36(r = 0.492, p = 0.013; r = 0.496, p = 0.016; r = 0.441, p = 0.025; r = 0.43, p = 0.032), respectively. Scores of mental health status (SDS and SAS) were negatively correlated with all SF-36 domains except PF and RP (r=-0.082, p = 0.651; r=-0.215, p = 0.225; r=-0.347, p = 0.054; r=-0.12, p = 0.949), respectively.
A comparison of SF-36 domain scores of the patients at 3, 6 and 12 months after discharge with normative data is shown in Table 6. The health status of COVID-19 survivors was still significantly impaired at 3, 6 and 12 months post-discharge compared to that of the normal control population of the same age groups.