Nonlinear association between plasma elaidic acid level and sleep complaints in US adults: NHANES 2009-2010

Poor sleep is linked to an increased risk of metabolic, cardiovascular, psychiatric, and neurodegenerative diseases, highlighting its emergence as a public health concern. Previous studies demonstrated the harmful effects of trans fatty acids (TFAs) on human health. However, the association between TFAs and sleep outcomes is still not well-established. The current study aimed to investigate the relationship between plasma elaidic acid, a major TFA, and sleep complaints. The participants from the US National Health and Nutrition Examination Survey (NHANES) (2009-2010) were included. The plasma concentration of elaidic acid (18:1n-9t) was determined using the gas chromatography/mass spectrometry (GC/MS) method. The sleep outcome was defined based on the following questionnaire: "Ever told the doctor had trouble sleeping?" and "Ever told by a doctor have a sleep disorder?". Participants were classified as having sleep complaints if they ever told a doctor or been told by a doctor about trouble sleeping. The association between plasma elaidic acid and sleep complaints was investigated by multivariable logistic regressions, restricted cubic spline (RCS), and subgroup analysis. A total of 2068 participants were included, 561 of whom suffered from sleep complaints. The restricted cubic spline (RCS) regression analysis revealed a nonlinear (inverted L-shaped) relationship between plasma elaidic acid level and sleep complaints (p = 0.044), with an inflection point of 9.598 μmol/L. In the group with a low plasma elaidic acid level (≤9.598 μmol/L), there was a positive association between plasma elaidic acid level and the prevalence of sleep complaints (OR 1.28; 95% CI: 1.06-1.54, p = 0.01). When the plasma elaidic acid level was more than 9.598 μmol/L, the correlation was not statistically significant. Results were robust when analyses were stratified by sex, age, race, marital status, education level, family income, and BMI (all p for interaction >0.05). The results revealed a positive association between plasma elaidic acid and sleep complaints in US adults when plasma elaidic acid level ≤9.598 μmol. Given that the plasma TFA content has considerably declined in recent years, the detrimental impact of elaidic acid on sleep quality deserves more attention.