Association between dietary fatty acid intake and preserved ratio impaired spirometry in U.S. adults: a population-based cross-sectional study

Abstract

Background: Preserved ratio impaired spirometry (PRISm) is increasingly recognized as a clinically relevant but underdiagnosed lung function abnormality. This pulmonary phenotype is clinically significant yet remains insufficiently studied. Although dietary fatty acids are known to have anti-inflammatory and immune-regulating properties, their relationship with PRISm has not been previously explored. This study aimed to evaluate the associations between intake of saturated (SFA), monounsaturated (MUFA), and polyunsaturated fatty acids (PUFA) and the prevalence of PRISm in U.S. adults.

Methods: We conducted a cross-sectional analysis using data from 9,103 adults in the 2007-2012 National Health and Nutrition Examination Survey (NHANES). Dietary intake of SFA, MUFA, and PUFA was assessed from two 24-h dietary recalls. Fatty acid variables were log-transformed and standardized. Logistic regression models were used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for the associations between fatty acid intake and PRISm, adjusting for sociodemographic, behavioral, and clinical covariates. Nonlinear relationships were examined using restricted cubic splines. A two-sided p-value <0.05 was considered statistically significant.

Results: Among the study population (mean age 45.6 ± 15.8 years; 47.7% male), 1,362 participants (15.0%) exhibited the PRISm phenotype. In models controlling for demographic, lifestyle, and clinical variables, each standard deviation increase in SFA [0.86 (0.75-0.99)] and PUFA [0.88 (0.79-0.99)] intake was associated with a statistically significant reduction in the odds of PRISm. MUFA intake was not significantly related to PRISm. Restricted cubic spline analysis indicated no evidence of non-linearity in these associations. The inverse relationships for SFA and PUFA were also consistent across demographic and clinical subgroups.

Conclusion: Greater consumption of saturated and polyunsaturated fatty acids was associated with a lower prevalence of PRISm in a nationally representative adult population. These associations were consistent across key demographic and clinical subgroups. If confirmed in prospective studies, our findings may inform early dietary strategies to support pulmonary health.

Keywords: NHANES; PRISm; dietary fatty acid; lung function; nutrition.

Figure 1

Flow chart of participant selection. NHANES, National Health and Nutrition Examination Survey; FEV, forced expiratory volume in one second; FVC, forced vital capacity.

Figure 2

Mean daily intake of SFA, MUFA and PUFA by sex. Bar plots show mean intake (g/day) ± SD of SFA, MUFA and PUFA, stratified by sex (green = male; orange = female). SFA, saturated fatty acids; MUFA, monounsaturated fatty acids; PUFA, polyunsaturated fatty acids; SD, standard deviation.

Figure 3

Associations between dietary fatty acids and PRISm. Forest plots display adjusted ORs and 95% CIs for PRISm according to quartiles (Q2–Q4 vs. Q1 reference) and per-SD increment of ln-transformed SFA, MUFA and PUFA. Model 1: none; Model 2: age, sex, and race; Model 3: Model 2 + energy intake, protein intake, carbohydrate intake, fat intake, education, BMI, PIR, smoking, alcohol drinking, hypertension, diabetes, and cancer. OR, odds ratio; CI, confidence interval; SD, standard deviation; PIR, poverty income ratio; BMI, body mass index.

Figure 4

Restricted cubic spline analyses of dietary fatty acids and PRISm. Restricted cubic spline curves for the association between ln-transformed fatty acid intake and odds of PRISm. Shaded areas represent 95% CIs. p-values for overall association and nonlinearity are shown in each panel. Models adjusted for Model 3. OR, odds ratio; CI, confidence interval; RCS, restricted cubic spline; PRISm, preserved ratio impaired spirometry.

Figure 5

Subgroup analyses of dietary fatty acids and PRISm. Forest plots of adjusted ORs (95% CIs) for PRISm by quartile and per-SD increment of fatty acids across prespecified subgroups (age, sex, race, education, PIR, BMI, hypertension, diabetes, cancer, smoking, drinking). Models adjusted for Model 3. OR, odds ratio; CI, confidence interval; SD, standard deviation; PIR, poverty income ratio; BMI, body mass index.