The present study investigated the data of the pulmonary function, physical activity, and QoL that of 121 COPD patients from the 31,649 test results of the KNHANES in 2015-2018. In subjective health status, those who answered “very good” to “normal” were 51.2%, and the subjects who answered “bad” and “very bad” were 47.0%. There was no specific feature because the proportion of good and bad in the self-assessed health status of COPD patients was almost similar. In physical activity that can represent physical health, only less than 20% of COPD patients performed regular physical activity. In addition, it was confirmed that the subjects spent more than 8 hours per day sitting on average. The Korean COPD patients had greater difficulty in “pain and discomfort” and “mobility”.
In the health-related characteristics examined in this study, more than 30% of the COPD subjects had hypertension and asthma. Pulmonary function impairment was found to be associated with a more comorbid disease, Global Initiative for Obstructive Lung Disease stage 3 or 4 COPD had a higher prevalence of diabetes, hypertension, and cardiovascular disease . In the health-related characteristics investigated in this study, COPD patients with a history of myocardial infarction or angina pectoris and diabetes were 10.7% and 13.2%, whereas those with hypertension were found to be relatively high as 37.2%. This study showed similar results that the proportion of COPD patients with hypertension was relatively high compared to other diseases, such as COPD patients of the United States .
To assess the crucial functioning of the lungs, PFT is essential. The American College of Physicians, American College of Chest Physicians, American Thoracic Society, and European Respiratory Society had recommended that spirometry can be used to identify airflow obstruction in patients with respiratory symptoms . The present study also evaluated pulmonary function using a spirometer to assess airway obstruction. Since there is no data on the normal value of Asians, it was compared with the data of the most similar Caucasians to compare the results of this study by setting the values corresponding to the average height and weight of all subjects as normal values. The normal value of FVC was 3.39 ℓ, and the predicted FVC was 80-120% . The results of present study demonstrated that the average of FVC was 3.17 ℓ, which was 0.22 ℓ lower than the normal value. Predicted FVC was found to be in the lowest normal range with 82.07%. The normal FEV1 value is 2.54 , and the predicted FEV1 is 80-120% . The FEV1 of Korean COPD patients was 0.59 ℓ/s low, and the predicted FEV1 was 72.63%, which was 7.37% lower than the lowest normal value. The normal value of the FEV1/FVC ratio was 75.8%, and the average of Korean COPD patients was 10.45% lower. The normal level of FEV6 was 3.20 ℓ/s, which was 0.26 ℓ/s low in Korean COPD patients, and 2.15 ℓ/s in FEF 25-75%, while 1.52 ℓ/s in Korean COPD patients was 0.63 ℓ/s low. Lastly, the normal level of PEF was 6.72 ℓ/s, but the Korean COPD patient was 5.40 ℓ/s, which was 1.32 ℓ/s low. As a result of this study, the average of all pulmonary functions except predicted FEV1 was lower than the normal value. It was possible to confirm the low pulmonary function value of Korean COPD patients since the FEV1/FVC ratio was 10.45% lower than normal. Comparing the average value of Korean COPD patients with the normal range, it can be considered that FEV1 is an important variable for confirming airway obstruction.
Physical activity can be defined as the amount of energy expenditure by the movement of skeletal muscles . It is dependent on various factors such as physiologic, behavioral, social, environmental, and cultural aspects. Besides, physical activities are correlated with maximal walked distance, level airway obstruction, and physical health status, the present study surveyed the physical activity of COPD patients.
Physical activity is characterized by type, intensity, duration, pattern, routine, and activity-related symptoms . COPD patients have significantly lowered physical activity than healthy subjects . To survey the level of physical activity of COPD patients, we examined high/medium intensity of physical activity related to sports, exercise, and leisure activities. Also, daily walking, continuous walking time, strengthening exercise, and sitting time a day were observed.
Only 8.3% of the subjects performed high intensity of physical activity and 18.2% of medium-intensity. Daily walking was 3.54 days per week, and continuous walking time at once was 55.34 minutes. In particular, the strengthening exercise was found to be less than a day per week, and the average sitting time per day was 8 hours and 18 minutes. Although only 36 of the subjects responded to the survey, it was confirmed that about half of the COPD patients who responded to the questionnaire had daily activity restrictions due to respiratory problems. We thought that it is important to improve the pulmonary function of COPD patients because restriction of daily activity is associated with lowering of physical activity .
In previous studies, physical activity levels can predict important outcomes in COPD, lower physical activity levels are associated with a higher risk of an exacerbation-related hospitalization [20, 21]. As a result, patients with COPD due to lowered levels of physical activity increase the risk of all-cause mortality after controlling for relevant confounding factors such as admission and exacerbation . From the results of this study, it is considered that COPD patients need more regular and diverse physical activities and decrease sitting time a day.
Due to the characteristics of COPD, such as airway obstruction, the patients gradually decrease daily activities. Thus, health-related QoL tends to decrease with COPD severity worsen , and impaired health status is a risk factor for exacerbations of the respiratory problem and hospitalization . The present study surveyed the EQ-5D-3L data of KNHANES, the highest percentage of reporting some problems was "pain and discomfort". The EQ-5D-3L scores are correlated with validated measures of disease severity including COPD admission, comorbidities, and physical activity . The health-related QoL may also change depending on variations of pulmonary function and physical activity in COPD patients [22, 26], it can be an important factor to manage the QoL of COPD patients by improving the level of pulmonary function and physical activity. The present study showed that over 30% complained of some problems in the "pain and discomfort" and "mobility" category of EQ-5D-3L. Considering that the rate of complaining of discomfort to “mobility” was high, it is thought the improvement of the quality of life is necessary by increasing the activity of COPD patients such as exercise and pulmonary rehabilitation. In future studies, it is considered necessary to compare the QoL with subjects without COPD.
In Korean COPD patients, the FEF1/FVC ratio was found to be lower than the normal range (>80%), and the degree of physical activity was also confirmed to be low. Therefore, it is considered that Korean COPD patients need medical treatment to improve pulmonary function and increase the frequency of physical activity for their improving the QoL.
Limitations of this study
This study has several limitations. First, the results of the present study may not be generalized to patients with COPD in other countries because many studies presented were related to South Korea. Another limitation, since the data of physical activity and QoL of KNHANES is a cross-sectional and self-reporting questionnaire, the results of this study is having weak evidence for COPD patients. Therefore, longitudinal studies are needed to confirm the exact level of physical activities and QoL. The third limitation was that this study compared the physical activities and health-related QoL with COPD patients, other factors had to be investigated to clarify the specific features of COPD. However, these factors affect COPD patients' medical status, daily life, future research may be necessary to determine the specific features that affect COPD patients or depending on the patient's condition.