Edited by: Joao Dts Anselmo, Hospital do Divino Espírito Santo, Portugal
Reviewed by: Inês Mendes, Hospital do Divino Espírito Santo, Portugal
Maria Ponte, Hospital do Divino Espírito Santo, Portugal
*Correspondence: Xiaosong Wang,
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Thyroid function is closely linked to circadian rhythms, but the relationship between the frequency of night eating and thyroid function remains unclear. Our study aimed to investigate the association between night eating frequency and its impact on thyroid function and sensitivity. This study included 6093 participants from the U.S. National Health and Nutrition Examination Survey (2007–2012). Night eating behavior was assessed through 24-hour dietary recall, with night eating frequency calculated on the basis of food intake between 10:00 PM and 4:00 AM. The thyroid hormone indices examined included T3, T4, FT3, FT4, TSH, TGA, Tg, and TPOAb, whereas thyroid hormone sensitivity was assessed via indices such as the FT3/FT4, TSHI, TT4RI, and TFQI. The associations between night eating frequency and thyroid function were analyzed via weighted univariate and multivariate linear regression analyses. Subgroup analyses and interaction test analyses were also employed to test this correlation. Compared with individuals who did not eat at night, those who ate more frequently at night had higher levels of Tg (OR 1.223 [95% CI 1.048, 1.429], p trend=0.015) but lower levels of T3 (OR 0.728 [95% CI 0.611, 0.868], p trend=0.235) and TPOAb (OR 0.728 [95% CI 0.611, 0.868], p trend=0.235). Subgroup analysis indicated that this association between Tg and night eating was stronger in the DM group (Tg: OR 1.49 [95% CI 1.15, 1.93]), p interaction=0.022) and that the association between TPOAb and night eating was stronger in the group without DM (TPOAb: OR 0.9 [95% CI 0.82, 0.97]), p interaction=0.003). Our findings suggest a significant association between night eating frequency and thyroid function. However, no statistically significant differences were found in thyroid sensitivity based on night eating frequency. Despite these findings, the hormone fluctuations observed were within normal clinical ranges. Further rigorously designed studies are needed to establish a causal relationship between night eating frequency and thyroid function.
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Thyroglobulin (Tg) is synthesized and stored within the thyroid follicular lumen (
Research on circadian rhythms indicates that in metabolically healthy adults, various metabolic cycles, insulin secretion and sensitivity, and energy expenditure follow a rhythmic pattern (
Several studies have demonstrated that disruptions in circadian rhythms can interfere with TSH secretion, thereby affecting thyroid function (
The data from 2007–2008, 2009–2010, and 2011–2012 were used for this study (n = 30442). We excluded 20039 individuals whose dietary recall data were unreliable and thyroid hormone indices were missing, 1366 participants younger than 18 years of age, 67 pregnant participants, 1043 participants with heart failure and cancer, 348 participants whose BMI and waist circumference data were missing, and 348 participants with thyroid disease. Overall, our sample consisted of 6093 participants (
Flowchart of the study population.
The baseline dietary intake data from 2007-2012 were gathered from the initial 24-hour dietary recall interview. This first recall was conducted in person by trained personnel at the NHANES mobile examination centers. Standardized protocols and measurement tools were used to assess the volume and dimensions of the food. During the interviews, the participants were asked to provide details about the quantity and timing of each food and beverage they consumed. The nutrient values were calculated via the Food and Nutrient Database for Dietary Studies (FNDDS).
The main exposure was the frequency of night eating. Night eating was defined as food consumption between 10:00 PM and 4:00 AM, on the basis of the natural light cycle rhythm in this study. The frequency of night eating was categorized into three groups: “No night eating”, “One time”, and “Two times and over”.
In this study, the levels of TT3, FT3, and TT4 were measured via a competitive binding immunoenzymatic assay. Free T4 was determined through a two-step enzyme immunoassay. Sensitive human thyroid-stimulating hormone was detected via a two-site “sandwich” immunoenzyme test. TgAb (TGA) and TPOAb (IU/mL) levels were evaluated via a sequential two-step immunoenzymatic “sandwich” assay, whereas Tg levels (ng/ml) were measured via a simultaneous one-step “sandwich” assay. Detailed instructions for sample collection and processing are discussed in the NHANES Laboratory/Medical Technologists Procedures Manual (LPM). The following is the calculation method for sensitivity to thyroid hormone indices:
FT3/FT4 is achieved by FT3/FT4 ratio=FT3/FT4, TSHI is achieved by TSHI= lnTSH+0.1345*FT4, TT4RI is achieved by TT4RI=FT4*TSH, TFQI is achieved by TFQI = cumulative distribution function (cdfFT4) – (1 – cdfTSH).
The covariates included age (years), sex (male/female), race/ethnicity (Mexican American/non-Hispanic Black/non-Hispanic White/other), education (below high school/high school/above high school), income (poor/not poor), smoking status (never/former/now), drinking status (yes/no), body mass index (<25/25~29/≥30), physical activity (yes/no), hours of sleep (<6h/6~8 h/>8 h), hyperlipidemia (yes/no), hypertension (yes/no), diabetes (DM, yes/no), obesity (yes/no), abdominal obesity (Aobesity,yes/no), UIC (urinary iodine concentration, <100 (deficient), 100-299 (normal), ≥300 µg/L (excess)) (
Hypertension was defined as a diagnosis of hypertension, the use of antihypertensive drugs, a systolic blood pressure ≥140 mm Hg, or a diastolic blood pressure ≥90 mm Hg. DM was defined as self-reported, diagnosed diabetes, glycohemoglobin≥ 6.5%, or fasting plasma glucose ≥126 mg/dL. Hyperlipidemia was defined as taking antihyperlipidemic drugs, TG ≥200 mg/dL, TC ≥150 mg/dL, HDL <40 mg/dL for males and <50 mg/dL for females, and LDL ≥130 mg/dL. Heart failure participants were those who were informed that they had heart failure. The cancer participants were those who had been told that they had cancer. Thyroid disease participants were those who were told that they had cancer-related thyroid disease, or thyroid antibody abnormalities were defined as TPOAb≥5.61 IU/ml or TGA≥4.11 IU/ml.
The Dietary Inflammatory Index (DII) is a credible measure of the extent to which dietary factors contribute to an individual’s inflammatory response (
The complex survey design factors involved in the NHANES, including weights, clustering, and stratification, were all considered as recommended by the NCHS analytical guidelines. Data analysis was performed via R version 4.3.0. Weighted multiple linear regression model were applied to evaluate the associations of the frequency of night eating with thyroid function and sensitivity, including FT3, FT4, TT3, TT4, TSH, TG, TGA, TPOAb, FT3/FT4, TSHI, TT4RI and TFQI (no-night eating group as a reference), in three different model. The results are expressed as OR with 95% confidence intervals (CIs). We adjusted for no variable in Model 1. Model 1 is the unadjusted model. Model 2 was adjusted for baseline sex, age, BMI, race, marital status, family income and education. Model3 were further adjusted for baseline alcohol consumption, smoking status, physical activity, the DII of night eating, urinary iodine concentration, DM status, hypertension status, obesity status, hyperlipidemia status, abdominal obesity status and =UIC=. Owing to the presence of outliers in the data, some data were log-transformed, including T3, T4, TSH, Tg, TGA, TPOAb and TT4RI. We performed subgroup analyses with categorical variables, including sex, age, BMI, race, alcohol consumption, smoking status, physical activity, DII of night eating, UIC, DM, hypertension, obesity, hyperlipidemia, and Aobesity. We performed interaction term tests to check for heterogeneity between subgroups. Weighted multiple linear regression model were applied to investigate the correlations among the frequency of night eating and biochemical variables, including serum urea nitrogen (Ur), serum creatinine (Cr), HDL, LDL, TC, TG, and the neutrophil–lymphocyte ratio (NLR). The results are expressed as OR values with 95% CIs. Three model (model 1, 2, and 3) were adjusted as described above. A two-tailed p value of less than 0.05 was considered significant. The baseline characteristics are expressed as the means ± Standard error of mean (SME) or numbers (percentages).
This study included 6093 participants from NHANES 2007–2012. The baseline characteristics of the participants across night eating frequencies are shown in
Baseline characteristics of the participants.
Overall |
No night eating (n=4829) | One time |
Two times and over (n=522) | p value | |
---|---|---|---|---|---|
Age | |||||
18~34 | 2143(35.18) | 1606(33.26) | 215(41.81) | 268(51.46) | <0.001 |
35~64 | 3332(54.68) | 2693(55.77) | 255(49.61) | 241(46.14) | |
≥65 | 618(10.14) | 530(10.97) | 44(8.57) | 13(2.4) | |
BMI | |||||
<25 | 2068(33.94) | 1593(32.98) | 187(36.35) | 204(39) | 0.219 |
25~29 | 1694(27.8) | 1371(28.4) | 124(24.04) | 130(24.96) | |
≥30 | 2331(38.26) | 1865(38.62) | 204(39.61) | 188(36.04) | |
Gender | |||||
Male | 3313(54.38) | 2556(52.93) | 295(57.26) | 335(64.09) | 0.001 |
Female | 2780(45.62) | 2273(47.07) | 220(42.74) | 187(35.91) | |
Race | |||||
Mexican American | 563(9.24) | 465(9.62) | 40(7.83) | 39(7.43) | <0.001 |
Non-Hispanic White | 3991(65.5) | 3218(66.64) | 329(63.88) | 314(60.09) | |
Non-Hispanic Black | 737(12.1) | 554(11.48) | 72(14.07) | 96(18.3) | |
Other | 801(13.15) | 592(12.26) | 73(14.22) | 74(14.19) | |
Marital | |||||
Yes | 3699(60.71) | 3020(62.54) | 270(52.47) | 256(49.02) | <0.001 |
No | 2394(39.29) | 1809(37.46) | 245(47.53) | 266(50.98) | |
PIR | |||||
Poor | 891(14.63) | 662(13.71) | 92(17.87) | 96(18.4) | 0.027 |
Not poor | 5202(85.37) | 4167(86.29) | 423(82.13) | 426(81.6) | |
Education | |||||
Below high school | 388(6.37) | 324(6.7) | 24(4.65) | 16(3.1) | 0.005 |
High School | 779(12.79) | 621(12.85) | 75(14.53) | 55(10.58) | |
Above high School | 4926(80.84) | 3885(80.45) | 416(80.82) | 451(86.31) | |
Smoke | |||||
Never | 3437(56.41) | 2782(57.6) | 272(52.8) | 257(49.25) | 0.001 |
Former | 1285(21.09) | 1032(21.38) | 108(20.95) | 95(18.15) | |
Now | 1372(22.51) | 1015(21.02) | 135(26.26) | 170(32.6) | |
Drink | |||||
Yes | 4331(71.08) | 3487(72.2) | 379(73.64) | 375(71.89) | 0.842 |
No | 1762(28.92) | 1342(27.8) | 136(26.36) | 147(28.11) | |
Activity | |||||
No | 3244(53.24) | 2569(53.19) | 296(57.45) | 251(48.08) | 0.053 |
Yes | 2849(46.76) | 2260(46.81) | 219(42.55) | 271(51.92) | |
Sleep time | |||||
<6 h | 869(14.27) | 647(13.39) | 91(17.67) | 98(18.72) | 0.021 |
6~8 h | 4848(79.56) | 3880(80.35) | 394(76.56) | 390(74.77) | |
>8 h | 376(6.17) | 302(6.26) | 30(5.76) | 34(6.51) | |
Hypertension | |||||
Yes | 1869(30.67) | 1501(31.09) | 156(30.27) | 138(26.41) | 0.243 |
No | 4224(69.33) | 3328(68.91) | 359(69.73) | 384(73.59) | |
Hyperlipidemia | |||||
Yes | 3892(63.87) | 3129(64.8) | 303(58.77) | 305(58.35) | 0.032 |
No | 2201(36.13) | 1700(35.2) | 212(41.23) | 217(41.65) | |
Obesity | |||||
Yes | 1970(32.34) | 1580(32.71) | 181(35.14) | 150(28.66) | 0.169 |
No | 4123(67.66) | 3249(67.29) | 334(64.86) | 372(71.34) | |
AObesity | |||||
Yes | 4132(67.81) | 3330(68.96) | 337(65.44) | 327(62.55) | 0.065 |
No | 1961(32.19) | 1499(31.04) | 178(34.56) | 195(37.45) | |
DM | |||||
Yes | 598(9.81) | 465(9.62) | 60(11.58) | 40(7.65) | 0.269 |
No | 5495(90.19) | 4364(90.38) | 455(88.42) | 482(92.35) | |
UIC | |||||
Deficient | 2020(33.15) | 1624(33.62) | 169(32.79) | 167(32) | 0.679 |
Normal | 1960(32.17) | 1572(32.55) | 156(30.29) | 163(31.27) | |
Excessive | 2113(34.68) | 1634(33.83) | 190(36.92) | 192(36.73) | |
|
0.48 ± 0.02 | 0 ± 0 | 2.17 ± 0.09 | 3.62 ± 0.04 | <0.001 |
|
1.83 ± 0.01 | 1.83 ± 0.01 | 1.81 ± 0.02 | 1.83 ± 0.02 | 0.756 |
|
7.74 ± 0.02 | 7.75 ± 0.02 | 7.64 ± 0.06 | 7.71 ± 0.07 | 0.195 |
|
3.23 ± 0.01 | 3.22 ± 0.01 | 3.26 ± 0.02 | 3.32 ± 0.02 | <0.001 |
|
0.79 ± 0 | 0.79 ± 0 | 0.79 ± 0.01 | 0.79 ± 0.01 | 0.97 |
|
1.75 ± 0.01 | 1.75 ± 0.02 | 1.83 ± 0.07 | 1.64 ± 0.04 | 0.044 |
|
0.66 ± 0 | 0.67 ± 0.01 | 0.64 ± 0.01 | 0.65 ± 0.01 | 0.094 |
|
14.83 ± 0.45 | 14.81 ± 0.55 | 14.25 ± 0.67 | 15.74 ± 0.71 | 0.004 |
|
0.86 ± 0.01 | 0.88 ± 0.01 | 0.77 ± 0.03 | 0.77 ± 0.04 | 0.07 |
|
4.2 ± 0.01 | 4.19 ± 0.01 | 4.24 ± 0.03 | 4.31 ± 0.03 | 0.006 |
|
1.76 ± 0.01 | 1.77 ± 0.01 | 1.78 ± 0.03 | 1.7 ± 0.03 | 0.041 |
|
173.36 ± 1.45 | 174.38 ± 1.59 | 179.02 ± 6.44 | 161.85 ± 4.48 | 0.008 |
|
-0.06 ± 0 | -0.07 ± 0 | -0.06 ± 0.01 | -0.07 ± 0.01 | 0.882 |
|
4.46 ± 0.02 | 4.49 ± 0.02 | 4.31 ± 0.07 | 4.29 ± 0.06 | 0.079 |
|
76.62 ± 0.28 | 76.56 ± 0.32 | 78.33 ± 0.92 | 77.2 ± 0.71 | 0.04 |
|
5.53 ± 0.01 | 5.53 ± 0.01 | 5.53 ± 0.04 | 5.49 ± 0.04 | 0.008 |
|
5.04 ± 0.01 | 5.07 ± 0.02 | 4.94 ± 0.05 | 4.89 ± 0.05 | 0.002 |
|
1.78 ± 0.02 | 1.74 ± 0.02 | 1.83 ± 0.07 | 1.9 ± 0.08 | 0.799 |
|
2.97 ± 0.01 | 2.99 ± 0.01 | 2.91 ± 0.04 | 2.79 ± 0.04 | 0.038 |
|
1.34 ± 0.01 | 1.35 ± 0.01 | 1.3 ± 0.02 | 1.3 ± 0.02 | 0.031 |
|
2.13 ± 0.01 | 2.12 ± 0.02 | 2.18 ± 0.05 | 2.06 ± 0.05 | 0.068 |
Continuous variables are presented as the means ± SEM, and p values were calculated via survey-weighted linear regression analysis. The categorical variables are presented as percentages, and p values were calculated via the survey-weighted chi-square test. BMI, body mass index; PIR, poverty income ratio; BMI, body mass index; Aobesity, abdominal obesity; DM, DM; UIC, urinary iodine concentration; DII, dietary Inflammatory Index of night eating; TT3, total triiodothyronine; TT4, total thyroxine; FT3, free triiodothyronine; FT4, free thyroxine; TSH, thyroid-stimulating hormone; Tg, thyroglobulin; TGA, thyroglobulin antibodies; TPOAb, thyroid peroxidase antibodies; FT3/FT4, FT3-FT4 ratio; TSHI, thyroid-stimulating hormone; TT4RI, thyrotroph thyroxine tesistance Index; TFQI, thyroid feedback quantile-based index; Ur, serum urea nitrogen; Cr, serum creatinine; TC, total cholesterol; TG, total triglycerides; LDL, low-density lipoprotein cholesterol; HDL, high-density lipoprotein cholesterol; NLR, neutrophil–lymphocyte ratio.
The association of frequency of night eating with thyroid function and thyroid hormone sensitivity were evaluated (
Association between the frequency of night eating and thyroid function and sensitivity. OR, odds ratio, Cl, confidence interval. * p < 0.05, ** p < 0.01, *** p < 0.001; p < 0.05 was considered statistically significant. Model: 1 unadjusted. Model 2: further adjusted for sex, age, BMI, race, marital status, education, and family income. Model 3: further adjusted for smoking behavior, physical activity, drinking behavior, sleep time, hypertension, hyperlipidemia, DM, UIC, and the Dill of night eating.
Compared with people who had no night eating, individuals who had more frequent of night eating were positively associated with FT3 (OR 1.099 [95% CI 1.055, 1.145], p trend=0.011) and negatively associated with TSH (OR 0.935 [95% CI 0.889, 0.984], p trend=0.025) in model 1. Moreover, compared with people who had no night eating, individuals who consumed one time at night were negatively associated with T3 (OR 0.867 [95% CI 0.769, 0.979], p trend=0.235) in model 3 and T4 (OR 0.982 [95% CI 0.966, 0.999], p trend=0.266) in model 2.
Further analyses of thyroid sensitivity revealed that, compared with no night eating, more frequent night eating behavior were positively associated with FT3/FT4 levels in model 1 (OR 1.127 [95% CI 1.037, 1.225], p trend=0.05) and model3 (OR 1.168 [95% CI 1.021, 1.337], p trend=0.516), but this association was not statistically significant in model 2. Conversely, a significantly negative association with the TSHI (OR 0.934 [95% CI 0.881, 0.991], p trend=0.051) and TT4RI (OR 0.928 [95% CI 0.883, 0.976], p trend=0.015) was detected in model 1, but no statistically significant association was detected in the other model.
Furthermore, weighted linear regression analysis was applied to investigate the relationships between the frequency of night eating and other biochemical variables (
The association of frequency of night eating and other laboratory biochemical variables. OR, odds ratio. Cl, confidence interval. * p < 0.05, ** p < 0.01, *** p < 0.001; p < 0.05 was considered statistically significant. Model 1: unadjusted. Model 2. further adjusted for sex, age, BMI, race, marital status, education, and family income. Model 3: further adjusted for smoking behavior, physical activity, drinking behavior, sleep time, hypertension, hyperlipidemia, DM, UIC, and the Dll of night eating.
Subgroup analyses were performed to examine the associations between eating frequency and T3, Tg, TGA, and TPOAb levels in various populations that were categorized according to age, BMI, sex, race, smoking status, alcohol consumption, physical activity, sleep time, hypertension, hyperlipidimia, obesity, Aobesity, DM, and UIC (
Subgroup analysis of association between night eating frequency and T3 levels. The "No night eating" group was used as a reference.
Subgroup analysis of association between night eating frequency and Tg levels. The "No night eating" group was used as a reference.
Subgroup analysis of association between night eating frequency and TGA levels. The "No night eating" group was used as a reference.
Subgroup analysis of association between night eating frequency and TPOAb levels. The "No night eating" group was used as a reference.
This study expands on existing research regarding night eating frequency and is the first, to our knowledge, to examine its relationship with thyroid function and sensitivity. To investigate this association, we analyzed data from a nationally representative cohort of U.S. adults. To reduce potential confounding factors, we excluded participants who were under 18 years of age, had cancer, had heart failure, were pregnant, or had thyroid disease. Our findings revealed a strong correlation between thyroid function indices and night eating frequency. Specifically, more frequent night eating was associated with higher levels of Tg and lower levels of T3 and TPOAb. Additionally, our study revealed that, compared with not eating at night, more frequent night eating was linked to lower LDL levels. Subgroup analysis, stratified by DM status, indicated that among participants with DM, increased night eating frequency might lead to more pronounced increases in Tg and TPOAb levels. Conversely, in healthy participants, frequent night eating was associated with a decrease in TPOAb levels. Notably, we observed that among participants aged 65 years and older, frequent night eating led to a relative increase in TGA levels, whereas the opposite effect was observed in those with UIC deficiency. Importantly, our results did not reveal a statistically significant difference between thyroid sensitivity and night eating frequency.
Regulating the timing of food intake throughout the day can influence the rhythmicity and regularity of certain aspects of the circadian system and related behaviors (
Importantly, we evaluated the night eating DII. The DII, proposed by J.R. Hébert et al. (
Thyroid hormones are reportedly related to pancreatic β-cell development and influence glucose metabolism through several organs (
A higher prevalence of thyroid disorders has been documented in people with DM than in normoglycemic individuals, whereas patients with both endocrinopathies have poorer glycemic control and are more vulnerable to the development of complications. We speculate that the reason for the elevated Tg levels may be that night eating caused an increase in blood glucose levels, prompting the secretion of thyroid hormones to participate in glucose homeostasis, which also positively affected the Tg level. Therefore, owing to the interaction effects, the Tg levels in DM participants increased more than those in participants who did not eat at night.
As we all know, iodine intake significantly affects thyroid function. Chronic exposure to excess iodine intake induces autoimmune thyroiditis, partly because highly iodinated Tg is more immunogenic (
Additionally, we focused on laboratory indicators such as renal function, glycated hemoglobin, blood lipids, and the NLR, in addition to thyroid function, with the intention of identifying any associations between these indicators and impaired thyroid function. Thyroid hormones are known to affect energy metabolism. Many patients with metabolic syndrome have subclinical or clinical hypothyroidism and vice versa (
Our study also had some limitations. First, the participants included in the study did not represent the entire population. Second, the frequency of night eating was obtained through dietary recall, the accuracy of which cannot be reliably estimated. Additionally, night eating information is only a single dietary recall and cannot represent long-term habits. Third, unknown and unmeasured confounding factors are likely present, so we cannot make strong causal inferences. Fourth, we could not determine whether participants were taking any medications or supplementation. Given the limitations mentioned above, the present results still need further confirmation by longitudinal prospective large cohort studies with accurate information.
Publicly available datasets were analyzed in this study. This data can be found here:
The studies involving humans were approved by National Center for Health Statistics. The studies were conducted in accordance with the local legislation and institutional requirements. The participants provided their written informed consent to participate in this study. Written informed consent was obtained from the individual(s) for the publication of any potentially identifiable images or data included in this article.
YZ: Conceptualization, Methodology, Software, Writing – original draft. SZ: Investigation, Software, Writing – review & editing. SL: Validation, Visualization, Writing – review & editing. YW: Investigation, Writing – review & editing. HZ: Software, Writing – review & editing. JW: Validation, Writing – review & editing. LW: Writing – review & editing. XW: Project administration, Supervision, Writing – review & editing.
The author(s) declare that no financial support was received for the research, authorship, and/or publication of this article.
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
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