Impact of the severity of restrictive spirometric pattern on nutrition, physical activity, and quality of life: results from a nationally representative database

Restrictive spirometric pattern (RSP) is characterized by reduced FEV1 and FVC with a preserved FEV1/FVC ratio and is classically associated with interstitial lung disease, pleural effusions, chest wall disease, neuromuscular disease, and diaphragmatic disorders. Recent studies show RSP is also seen in aging and in extra-thoracic conditions including diabetes mellitus, heart failure, metabolic syndrome, and obesity, with a prevalence of about 7–13% in the general population. RSP has been linked to functional impairment, fair/poor health, increased respiratory symptoms, multiple comorbidities, poor quality of life, and mortality. However, whether general health problems and quality of life worsen proportionally with increasing severity of RSP remains unclear. This study aimed to investigate how RSP severity relates to nutrition, physical activity, and quality of life using a nationally representative Korean database.

Prior analyses (e.g., NHANES) reported that individuals with RSP have higher rates of functional limitations and poor self-reported health compared with those with normal spirometry. RSP has been associated with increased respiratory symptoms, multiple comorbidities (e.g., diabetes, cardiovascular disease), poorer health-related quality of life, and increased mortality. Studies such as ECRHS and SAPALDIA linked RSP to deficits in quality of life independent of respiratory symptoms. RSP has also been tied to obesity, metabolic syndrome, and insulin resistance. Despite these findings, the literature had not clarified whether the burden of these adverse outcomes scales with the severity of RSP, nor did it detail relationships with daily diet intake; the present study addresses these gaps.

Design and data source: Cross-sectional analysis of the Korea National Health and Nutrition Examination Survey (KNHANES), 2007–2016, a nationally representative survey using stratified, multistage clustered probability sampling. KNHANES protocols were IRB-approved; all participants gave written informed consent. Population: Adults with available pulmonary function test (PFT) results from 2007–2016 were included; those with obstructive spirometric pattern were excluded. Final analytic sample: n=23,615 after exclusions. Spirometry and classification: Spirometry followed ATS/ERS standards. Predicted values for FEV1 and FVC used Korean reference equations. Categories: Normal spirometry defined as pre-bronchodilator FEV1/FVC ≥0.70 and FVC ≥80% predicted. Obstructive pattern defined as pre-bronchodilator FEV1/FVC <0.70 (excluded). RSP defined as pre-bronchodilator FEV1/FVC ≥0.70 with FVC <80% predicted, further subdivided into mild-to-moderate RSP (60%≤FVC<80% predicted) and severe RSP (FVC<60% predicted). Measures: Demographics, education, smoking, family income, medical history, and medication use were self-reported. Comorbidities included hypertension, dyslipidemia, diabetes mellitus, cardiovascular disease, asthma, osteoporosis, osteoarthritis, and malignancy (based on self-report of physician diagnosis and labs). Physical activity definitions: moderate intensity (activities causing small increases in breathing/heart rate for ≥10 min continuously, e.g., brisk walking, carrying light loads); high intensity (large increases in breathing/heart rate for ≥10 min, e.g., heavy lifting, digging, construction work). Quality of life measured by EQ-5D index (0 to 1); poor quality defined as EQ-5D<0.90 (25th percentile cutoff). Nutrition assessed via total daily caloric intake (kcal) and macronutrient components. Outcomes: Primary outcomes were nutrition (total kcal/day), physical activity (rate and days of high-intensity activity in the past week), and quality of life (EQ-5D<0.90). Statistical analysis: All analyses used PFT subsample weights and survey procedures in STATA 13.1 to account for complex sampling. Univariable and multivariable linear regression assessed associations of RSP severity with total calories. Univariable and multivariable logistic regression assessed associations with high-intensity physical activity, EQ-5D<0.90, and EQ-5D components. Multivariable models adjusted for age (≥65 vs <65), sex, smoking status (never vs current/ex), BMI (≥25 vs 18.5–<25 vs <18 kg/m2), education (high school or less vs college or above), family income (upper half vs lower half), and number of comorbidities (≤1 vs ≥2). Effect modification by sex was assessed with likelihood ratio tests for interaction across spirometric categories and sex, with results presented overall and stratified by sex.

- Sample: Of 81,503 KNHANES participants (2007–2016), 27,095 without spirometry and 27,211 missing weights were excluded; among 27,197 with data, 3,582 with obstruction were excluded, yielding 23,615 participants: 20,742 normal, 2,758 mild-to-moderate RSP, 115 severe RSP. - Baseline characteristics: Compared with normal spirometry, RSP groups were older (mean age: 49.7 normal; 55.4 mild-to-moderate; 64.1 severe; P<0.001), had larger waist circumference (82.5; 86.5; 85.9 cm; P<0.001), and lower education (high school or less: 70.8% normal; 76.4% mild-to-moderate; 93.2% severe; P<0.001). Severe RSP had higher prevalence of diabetes (30.2%), hypertension (55.4%), cardiovascular diseases (14.9%), osteoporosis (27.0%), osteoarthritis (40.2%), and malignancy (10.8%) (all P<0.001 vs normal). - Nutrition: Total caloric intake decreased with RSP severity: mean kcal/day 2001.4 (normal), 1935.9 (mild-to-moderate), 1661.1 (severe) (P<0.001). Adjusted linear regression vs normal: mild-to-moderate RSP coefficient −56.6 kcal (95% CI −101.9 to −11.4); severe RSP −286.7 kcal (95% CI −431.7 to −141.6). Similar trends in male and female subgroups. - Physical activity: High-intensity physical activity prevalence: 16.8% (normal), 14.5% (mild-to-moderate), 6.8% (severe) (P=0.018). Days/week of high-intensity activity: 2.5 (normal), 2.8 (mild-to-moderate), 1.6 (severe) (P<0.001). Univariable ORs for high-intensity activity vs normal: mild-to-moderate 0.84 (95% CI 0.71–0.99), severe 0.36 (0.14–0.95); associations attenuated and not significant after adjustment overall. - Quality of life: EQ-5D index lowest in severe RSP (0.88 vs 0.95 normal and 0.92 mild-to-moderate; P<0.001). Proportion with EQ-5D<0.90: 16.6% (normal), 24.6% (mild-to-moderate), 40.5% (severe) (P<0.001). ORs for EQ-5D<0.90 vs normal: unadjusted—mild-to-moderate 1.64 (1.46–1.84), severe 3.43 (2.20–5.33); adjusted—mild-to-moderate 1.26 (1.10–1.43), severe 1.96 (1.22–3.17). Severe RSP associated with worse self-care (adjusted OR 2.64, 1.37–5.10) and usual activities (2.15, 1.28–3.61) components. - Sex interactions: Trends for poorer quality of life and lower high-intensity physical activity with increasing RSP severity were significant in males in both uni- and multivariable analyses, but in females the associations were weaker and mostly not significant after adjustment (P for interaction <0.001). - Spirometry metrics: Mean FVC %pred: 95.7 (normal), 74.5 (mild-to-moderate), 54.1 (severe); FEV1 %pred: 96.0, 78.0, 59.1; FEV1/FVC ~0.80–0.81 across groups.

This study shows that general health detriments scale with the severity of restrictive spirometric pattern. Individuals with severe RSP had substantially lower caloric intake, less high-intensity physical activity, higher comorbidity burden, and significantly worse quality of life compared with those with normal spirometry, with intermediate findings in mild-to-moderate RSP. These results extend prior work linking RSP to functional impairment and poor health by demonstrating a dose–response relationship with RSP severity. The association with lower caloric and macronutrient intake despite higher BMI suggests complex interactions between age, comorbidity burden, physical inactivity, and diet in RSP. Clinically, findings support assessing and addressing modifiable factors—particularly physical inactivity and obesity—in individuals with RSP, with attention to severity. Importantly, the observed associations were more pronounced in males, indicating possible sex-specific pathways or exposures that merit further investigation. Overall, the results underscore the need for clinicians to consider RSP severity when evaluating patient health status and planning management.

In a nationally representative Korean sample, increasing severity of restrictive spirometric pattern was associated with lower caloric intake, reduced rates and days of moderate- and high-intensity physical activity, higher prevalence of multiple comorbidities, and poorer quality of life compared with normal spirometry. These impacts were more pronounced in males. Recognizing RSP severity alongside its presence may help identify individuals at higher risk and guide interventions targeting modifiable factors such as physical inactivity and obesity. Future research should use longitudinal designs to clarify causality, explore mechanisms—including sex differences—and test whether targeted interventions can improve RSP-related outcomes.

- Cross-sectional design limits causal inference and raises potential for reverse causation (e.g., severe RSP leading to lower activity and caloric intake vs vice versa). - Generalizability may be limited as the study population represents Korea; race/ethnicity differences could influence findings. - Potential information bias due to self-reported demographics, smoking, income, and medical history. - Lack of post-bronchodilator spirometry could lead to misclassification of spirometric patterns in some participants.