Purpose: This study aimed to evaluate the prevalence, trends, and factors of preserved ratio with impaired spirometry (PRISm) by using a nationally representative sample. Patients and methods: The datasets of the Korea National Health and Nutrition Examination Survey 2010–2019 were used: of total 32,949 participants aged ≥40 and no missing data on spirometry, 24,523 with normal, 4,623 with obstructive, and 3,803 with PRISm were identified. PRISm was defined as FEV₁/FVC ≥70% and FEV₁% of the predicted value (%pred) <80. PRISm-lower limit of normal (LLN) was defined when FEV₁/FVC ≥LLN and FEV₁ <LLN. The prevalence and trend of PRISm were estimated using the Joinpoint regression method. The trend was calculated for the periods 2010–2015 and 2017–2019, due to a change in spirometry device in June, 2016. A complex sample multivariable-adjusted regression model was used to identify factors associating PRISm. Results: Estimated average prevalence of PRISm was 10.4% (PRISm-LLN 11.1%). Joinpoint regression analyses found a relatively stable trend of PRISm for both fixed ratio and LLN. The multivariable-adjusted logistic regression model showed female sex, BMI ≥25 kg/m², metabolic syndrome, hypertriglyceridemia, abdominal obesity, low HDL-choleterol, hypertension, and diabetes were associated with the increased probability of PRISm. Conclusion: Whenever a PRISm pattern is identified in a clinical context, it may be necessary to measure absolute lung volumes to investigate underlying physiological abnormalities and to identify factors that is modifiable.

Background: Autonomic neuropathy commonly occurs as a long-term complication of diabetes mellitus (DM) and can be diagnosed based on heart rate variability (HRV), calculated from electrocardiogram (ECG) recordings. There are limited data on HRV using real-time ECG and ambulatory glucose monitoring in patients with DM. The aim of this study was to investigate real-time HRV according to ambulatory glucose levels in patients with DM.Methods: A total of 43 patients (66.3 ± 7.5 years) with DM underwent continuous real-time ECG monitoring (225.7 ± 107.3 h) for HRV and ambulatory glucose monitoring using a remote monitoring system. We compared the HRV according to the ambulatory glucose profile. Data were analyzed according to the target in glucose range (TIR).Results: There were no significant differences in the baseline characteristics of the patients according to the TIR. During monitoring, we checked ECG and ambulatory glucose levels (a total of 15,090 times) simultaneously for all patients. Both time- and frequency-domain HRVs were lower when the patients had poorly controlled glucose levels (TIR < 70%) compared with well controlled glucose levels (TIR > 70%). In addition, heart and respiratory rates increased with real-time glucose levels (P < 0.001).Conclusions: Poorly controlled glucose levels were independently associated with lower HRV in patients with DM. This was further substantiated by the independent continuous association between real-time measurements of hyperglycemia and lower HRV. These data strongly suggest that cardiac autonomic dysfunction is caused by elevated blood sugar levels.

Folate, folic acid, has a role in mitigating inflammatory reactions in the human body. This study aimed to evaluate the association of serum folate levels with lung function in chronic obstructive pulmonary disease (COPD) patients. Of the 8149 participants of the 2016 Korean National Health and Nutrition Examination Survey (KNHANES), 311 subjects (192 males and 119 females) having COPD defined by the lower fifth percentile of the reference population were selected. Pearson’s correlation coefficient was used to investigate the relationship between serum folate level and lung function measurements. The association between the serum folate level and lung function in patients with COPD was evaluated using multivariable linear regression analysis after adjustment for age, sex, height, high sensitivity C-reactive protein, total calorie intake, residence, smoking status and smoking pack–years, education, and household income. The serum folate level showed a positive correlation with the predicted percentage of forced expiratory volume in one second (FEV₁%). In males, a trend for a positive correlation with serum folate level was observed in predicted FEV₁%, FEV₁ value, predicted percentage of forced vital capacity (FVC%), FVC value, and peak expiratory flow (PEF). No significant correlation between the serum folate level and lung function in females was observed. In the multivariable linear regression model, the serum folate level was associated with an increase in predicted FEV1%, FEV₁ value, predicted FVC%, FVC value, and PEF; however, the significance was only observed in males, especially among current smokers. High serum folate level was positively associated with lung function measurements in male COPD patients who were current smokers. Further longitudinal studies are needed to elucidate the underlying mechanisms.