Serum nutritional biomarkers and their associations with sleep among US adults in recent national surveys

Abstract

Background: The associations between nutritional biomarkers and measures of sleep quantity and quality remain unclear.

Methods: Cross-sectional data from the National Health and Nutrition Examination Surveys (NHANES) 2005-2006 were used. We selected 2,459 adults aged 20-85, with complete data on key variables. Five sleep measures were constructed as primary outcomes: (A) Sleep duration; (B) Sleep disorder; (C) Three factors obtained from factor analysis of 15 items and labeled as "Poor sleep-related daytime dysfunction" (Factor 1), "Sleepiness" (Factor 2) and "Sleep disturbance" (Factor 3). Main exposures were serum concentrations of key nutrients, namely retinol, retinyl esters, carotenoids (α-carotene, β-carotene, β-cryptoxanthin, lutein+zeaxanthin, lycopene), folate, vitamin B-12, total homocysteine (tHcy), vitamin C, 25-hydroxyvitamin D (25(OH)D) and vitamin E. Main analyses consisted of multiple linear, logistic and multinomial logit models.

Results: Among key findings, independent inverse associations were found between serum vitamin B-12 and sleep duration, 25(OH)D and sleepiness (as well as insomnia), and between folate and sleep disturbance. Serum total carotenoids concentration was linked to higher odds of short sleep duration (i.e. 5-6 h per night) compared to normal sleep duration (7-8 h per night).

Conclusions: A few of the selected serum nutritional biomarkers were associated with sleep quantity and quality. Longitudinal studies are needed to ascertain temporality and assess putative causal relationships.

Figure 1. Relative risk ratio (RRR with 95% CI) per 1 SD nutritional biomarker: (A) Insomnia vs. Normal sleep duration^a,b, (B) Other sleep disorder categories vs. None^a,b.

Abbreviations: BMI = Body Mass Index; CI = confidence interval; Met = Metabolic Equivalent; n-3 HUFA = omega-3 highly unsaturated fatty acids; NHANES = National Health and Nutrition Examination Survey; RRR = relative risk ratio; SEE = Standard error of the estimate. ^a Values are Relative Risk Ratios (RRR) with 95% confidence intervals. Sampling design complexity is taken into account in all analyses. ^b Models included all serum nutritional biomarker exposures simultaneously, and adjusted for socio-demographic factors: age, sex, race/ethnicity, marital status, educational level and poverty income ratio, and other potential confounders: Lifestyle and health-related factors (smoking status, BMI, physical activity: Mets.hr.wk⁻¹, history of selected chronic conditions (i.e. type 2 diabetes, CVD and cancer)), anti-depressant use and dietary intakes (total energy intake, alcohol, caffeine, fiber, n-3 HUFA, each of the five carotenoids, vitamin C, vitamin E, folate, vitamin B-12), fruit and vegetable intake, supplement use, anti-depressant use, and the inverse mills ratio, 2-stage Heckman selection model as well as serum cholesterol (See Table 4 , Model 4 for more details).

Figure 2. Relative risk ratio (RRR with 95% CI) per 1 SD nutritional biomarker: (A) Very short sleep vs. Normal sleep duration^a,b, (B) Short sleep vs. Normal sleep duration^a,b, (C) Long sleep vs. Normal sleep duration^a,b.

Abbreviations: BMI = Body Mass Index; CI = confidence interval; Met = Metabolic Equivalent; n-3 HUFA = omega-3 highly unsaturated fatty acids; NHANES = National Health and Nutrition Examination Survey; RRR = relative risk ratio; SEE = Standard error of the estimate. ^a Values are Relative Risk Ratios (RRR) with 95% confidence intervals. Sampling design complexity is taken into account in all analyses. ^b Models included all serum nutritional biomarker exposures simultaneously, and adjusted for socio-demographic factors: age, sex, race/ethnicity, marital status, educational level and poverty income ratio, and other potential confounders: Lifestyle and health-related factors (smoking status, BMI, physical activity: Mets.hr.wk⁻¹, history of selected chronic conditions (i.e. type 2 diabetes, CVD and cancer)), anti-depressant use and dietary intakes (total energy intake, alcohol, caffeine, fiber, n-3 HUFA, each of the five carotenoids, vitamin C, vitamin E, folate, vitamin B-12), fruit and vegetable intake, supplement use, anti-depressant use, and the inverse mills ratio, 2-stage Heckman selection model as well as serum cholesterol (See Table 4 , Model 4 for more details).