Taste Preference for Salt Predicts Salt Intake in a Chinese Population.

OBJECTIVE: This study describes the association between taste preference for salt and actual salt intake, thus guiding and refining personal and public health campaigns designed to lower salt intake in China. METHODS: A cross-sectional survey of 1489 residents aged 18 to 69 years was conducted in 2017 in China. A multistage random sampling strategy was used, and a combination of questionnaires and physical and laboratory measurements were conducted to collect baseline characteristics and knowledge, attitudes, and behavior (KAB) related to salt. A 24 h urine collection was obtained for sodium and potassium excretion analysis. Participants were divided into two groups, light taste preference and salty taste preference, according to their answer to the question "Compared to others, how do you think your taste preference is for salt?". RESULTS: The mean age of the 1489 participants was 46.26 years, 48.9% were males, over 1/3 (35.7%) were identified as hypertensive, and 317 (21.3%) self-reported a salty taste preference. The mean of 24 h urinary sodium excretion was 167.32 mmol/24 h, corresponding to 9.79 g salt/d intake, and the sodium-to-potassium ratio (Na/K) was 4.90. The 24 h urinary sodium excretion of salty taste preference (177.06 mmol/24 h) was significantly higher than that of light taste preference (164.69 mmol/24 h). The multiple logistic regression analysis showed that the salty taste preference group had significantly higher 24 h urinary sodium (ORa(95%CI) = 1.004(1.002-1.006)), diastolic blood pressure (DBP), proportion of greasy food preference, and drinking levels, but lower potassium excretion, response levels to most KAB questions, and regular physical activity compared to the light taste preference group. CONCLUSION: Self-reported taste preference for salt predicted actual salt intake, which was verified by 24 h urinary sodium monitoring. Taste preference for salt could be used as a proxy for intake in terms of targeted salt intake, nutrition, and health education.

Association of 24-h urinary sodium excretion with microalbuminuria in a Chinese population.

To assess the relationship of sodium, potassium and the ratio of sodium to potassium (Na/K) with albuminuria, a cross-sectional study was carried out in China in 2017. Sodium, potassium and albumin excretions were examined in a 24-h (h) urine sample collected from 1486 participants. Microalbuminuria was defined as 24-h urinary albumin excretion between 30 and 300 mg/24 h. The participants had an average age of 46.2 ± 14.1 years old, and 48.9% were men. The proportion of patients with microalbuminuria was 9.0%. As illustrated by the adjusted generalized linear mixed model, sodium concentration increased significantly with the increase in 24-h urinary albumin (ß = 1.16, 95% confidence interval (CI) 0.38-1.93; P = 0.003). Multivariable-adjusted logistic regression analyses demonstrated that the odds ratio (OR) of microalbuminuria increased with the quartiles of sodium [OR = 2.20, 95% CI 1.26-3.84 (the maximum quartile vs. the minimum quartile), Pfor trend = 0.006]. Potassium and the Na/K ratio did not have any association with outcome indicators. A high amount of sodium intake was potentially correlated with early renal function impairment.

The association of knowledge, attitudes and behaviors related to salt with 24-h urinary sodium, potassium excretion and hypertensive status.

To understand the association between sodium and potassium consumption levels, hypertension and knowledge, attitudes and behaviors (KAB) toward salt and the commitment to effective sodium reduction and potassium supplementation to achieve the purpose of suppressing hypertension. A stratified multistage random sampling method was used to obtain a representative provincial sample of 7512 residents aged 18-69 years through a cross-sectional survey by the Salt Reduction and Hypertension Prevention Project (SRHPP) in Zhejiang Province of China in 2017-2018. A screening including demographic, anthropometric, salt-related KAB and physical measurements was implemented, and 24-h urine of approximately 1/5 of the participants was collected and tested. The mean age was 44.8 years, 50.1% were women, 44.0% lived in urban areas, and hypertension or prehypertension accounted for approximately 35.0%. The mean 24-h urinary sodium and potassium excretion were 3848.5 (1661.1) mg/d and 1491.1 (710.9) mg/d, respectively. KAB in urban areas was generally more favorable than in rural areas, women were better than men, and the optimal blood pressure group was better than the other two groups (P < 0.05). However, the awareness and correct use rate of salt-restricted spoons, low-sodium salt and nutrition labeling were lower. A multivariable linear regression model indicated that KAB had a smaller effect on sodium (two indicators effective for promoting sodium reduction) and a greater effect on potassium (six indicators effective for promoting potassium supplementation) and mainly focused on knowledge and behavior indicators. A multivariable logistic regression model indicated that mastering more knowledge and taking active measures could effectively reduce the transition to hypertension, even if the individual was already in prehypertension. There is much room for improvement of salt-related KAB in the Chinese population. A clear association indicates that KAB can help to reduce sodium and supplement potassium, especially potassium, and help to suppress the development of hypertension. The role of beliefs in KAB should be fully valued and improved, similar to knowledge and behaviors. This study provides important evidence and insight into China's efforts to meet the targets of salt reduction and hypertension prevention.

Validity of predictive equations for 24-h urinary sodium excretion at the population and individual levels among Chinese adults aged 18-69 years.

Spot urine (SU) collection is a convenient method commonly used for sodium estimation, but its validity in predicting 24-h urinary sodium (24-hUNa) excretion has not been thoroughly evaluated among the general population. The aim of this study was to comprehensively assess the validity of eight existing methods in predicting 24-hUNa excretion by using SU samples among Chinese adults. We analyzed 1424 representative individuals aged 18 to 69 years. We compared the measured and estimated measurements of 24-hUNa at the population level by examining bias, the correlation, intraclass correlation coefficients (ICCs), receiver operating characteristic (ROC) curves and Bland-Altman plots and analyzed the relative and absolute differences and misclassification at the individual level. The bias for all methods was significant (all p < 0.001), among which the smallest bias was - 7.9 mmol for the Toft formula and the largest bias was - 53.8 mmol for the Mage formula. Correlation coefficients were all less than 0.380, all formulas exhibited an area under the ROC curve below 0.683, and the Bland-Altman plots indicated slightly high dispersion of the estimation biases at higher sodium levels regardless of the formula. The proportions of relative differences > 40% for the eight methods were all over one-third, the proportions of absolute differences > 51.3 mmol/24 h (3 g/day NaCl) were all over 40%, and the misclassification rates (7, 10, and 13 g/day NaCl as cutoff points) were all over 65%. Caution remains due to poor validity between estimated and actual measurements when using the eight formulas to obtain a plausible estimation for surveillance of the Chinese population sodium excretion, and the results do not support the application of SU to estimate sodium intake at the individual level due to its poor performance with respect to classification.

Use of Salt-Restriction Spoons and Its Associations with Urinary Sodium and Potassium in the Zhejiang Province of China: Results of a Population-Based Survey.

In China, a major source of sodium is salt added during cooking. In this context, use of a salt-restriction spoon (SRS) has been promoted in public health campaigns and by health care providers. To describe use of and factors associated with SRS use, knowledge of correct use, and actual correct use. This study is a population-based, representative survey of 7512 residents, aged 18 to 69 years, of China's Zhejiang Province. The survey, which was conducted in 2017 using a multistage random sampling strategy, collected demographic information, SRS use, and physical measurements; a 24-h urine collection was obtained from 1,496 of the participants. The mean age of the participants was 44.8 years, 50.1% were females, and over 1/3 (35.3%) were classified as hypertensive. Mean 24-h urinary sodium and potassium excretions were 167.3(72.2) mmol/24 h and 38.2(18.2) mmol/24 h, respectively. Only 12.0% (899/7512) of participants once used or were currently using SRS; of the 899 users, 73.4% knew how to use the SRS correctly, and just 46.5% actually used it correctly. SRS use was more commonly associated with behavioral factors rather than socio-demographic factors. Initiation of SRS use by health care providers was associated with correct technical knowledge of SRS. Lower sodium-to-potassium ratio was associated with SRS use, while SRS use was not associated with urinary sodium and potassium excretion. Use of SRS was uncommon in Zhejiang Province of China. Given that a common source of sodium in China is salt added during cooking, use of SRS is an appealing strategy, ideally as part of a multi-component campaign.

Association between 24-h urinary sodium and potassium excretion and blood pressure among Chinese adults aged 18-69 years.

The direction and magnitude of the association between sodium and potassium excretion and blood pressure (BP) may differ depending on the characteristics of the study participant or the intake assessment method. Our objective was to assess the relationship between BP, hypertension and 24-h urinary sodium and potassium excretion among Chinese adults. A total of 1424 provincially representative Chinese residents aged 18 to 69 years participated in a cross-sectional survey in 2017 that included demographic data, physical measurements and 24-h urine collection. In this study, the average 24-h urinary sodium and potassium excretion and sodium-to-potassium ratio were 3811.4 mg/day, 1449.3 mg/day, and 4.9, respectively. After multivariable adjustment, each 1000 mg difference in 24-h urinary sodium excretion was significantly associated with systolic BP (0.64 mm Hg; 95% confidence interval [CI] 0.05-1.24) and diastolic BP (0.45 mm Hg; 95% CI 0.08-0.81), and each 1000 mg difference in 24-h urinary potassium excretion was inversely associated with systolic BP (- 3.07 mm Hg; 95% CI - 4.57 to - 1.57) and diastolic BP (- 0.94 mm Hg; 95% CI - 1.87 to - 0.02). The sodium-to-potassium ratio was significantly associated with systolic BP (0.78 mm Hg; 95% CI 0.42-1.13) and diastolic BP (0.31 mm Hg; 95% CI 0.10-0.53) per 1-unit increase. These associations were mainly driven by the hypertensive group. Those with a sodium intake above about 4900 mg/24 h or with a potassium intake below about 1000 mg/24 h had a higher risk of hypertension. At higher but not lower levels of 24-h urinary sodium excretion, potassium can better blunt the sodium-BP relationship. The adjusted odds ratios (ORs) of hypertension in the highest quartile compared with the lowest quartile of excretion were 0.54 (95% CI 0.35-0.84) for potassium and 1.71 (95% CI 1.16-2.51) for the sodium-to-potassium ratio, while the corresponding OR for sodium was not significant (OR, 1.28; 95% CI 0.83-1.98). Our results showed that the sodium intake was significantly associated with BP among hypertensive patients and the inverse association between potassium intake and BP was stronger and involved a larger fraction of the population, especially those with a potassium intake below 1000 mg/24 h should probably increase their potassium intake.

Assessment and validation of spot urine in estimating the 24-h urinary sodium, potassium, and sodium/potassium ratio in Chinese adults.

The commonly used methods of estimating the 24-h urinary sodium (UNa) and urinary potassium (UK) from spot urine (SU) are the Kawasaki method (K-method), INTERSALT method (I-method), and Tanaka method (T-method), but the method that is suitable for use in the general Chinese population is still uncertain. We aimed to assess and validate these methods in estimating the 24-h UNa and UK using SU samples in Chinese adults. We studied 1428 individuals aged 18-69 years using SU and 24-h urine samples. For the K-method, I-method, and T-method, the Pearson correlation coefficients of the 24-h UNa were 0.35, 0.35, and 0.33 (all p < 0.01), and the intraclass correlation coefficients (ICC) were 0.34, 0.26, and 0.26 (all p < 0.01), respectively. The estimated 24-h UK using the K-method and T-method had correlation coefficients of 0.36 and 0.39 (all p < 0.01) and ICCs of 0.31 and 0.27 (all p < 0.01). The mean bias for the K-method in estimating the 24-h UNa and UK were the least biased among these methods. The bias between the 24-h urine Na/K ratio and the spot urinary Na/K ratio by the Bland-Altman method was -0.22. These methods for estimating the 24-h UNa and UK from SU were inadequate at the population level in Zhejiang Province, although the K-method showed the least bias among these methods. The spot urine Na/K ratio may be a useful and alternative method for 24-h urine collection for the estimation of the urinary Na/K ratio in the Chinese population.

Prevalence, awareness, treatment and control of hypertension and sodium intake in Zhejiang Province, China: A cross-sectional survey in 2017.

BACKGROUND: In recent decades, hypertension has become a popular public health problem in China. In 2017, a cross-sectional survey about hypertension and sodium intake measured by 24-hour (24-h) urine was launched in Zhejiang Province, to provide the basis of the Chinese population to develop a salt reduction intervention and prevention of hypertension strategy. METHODS: Cross-sectional data were obtained from 7512 participants aged 18 to 69 years in Zhejiang Province of China by complex, multistage sampling methods. The survey included face-to-face questionnaires and physical examination among all participants. Blood pressures and the use of anti-hypertension medications were used to determine hypertension. One thousand five hundred participants of them were asked to collect 24-h urine to measure sodium and potassium levels to assess intake. All rates and means were weighted by sampling weight and population structure of the province. RESULTS: The weighted means of systolic blood pressure (SBP) and diastolic blood pressure (DBP) were 127.78 mm Hg (95% confidence interval [CI], 127.21-128.36) and 79.40 mm Hg (95%CI, 79.04-79.76). The weighted hypertension prevalence was 30.41% (95%CI, 28.91-31.91). Among those classified as having hypertension, 43.55% (95%CI, 40.77-46.34) were aware of the fact that they were suffering from hypertension, 32.05% (95%CI, 29.49-34.61) of them reported taking anti-hypertension medications, only 14.48% (95%CI, 12.54-16.42) had their blood pressure controlled. The weighted means of 24-h urinary sodium was 165.52 mmol (standard deviation [SD], 2.92), representing that the mean intake of sodium chloride was 9.68g (SD, 0.17) through conversion. CONCLUSION: These cross-sectional survey results show that hypertension and excessive sodium intake in adults are prevalent in Zhejiang Province, China. Salt reduction and prevention of hypertension is still an urgent public health work.

Associations of blood metal exposure with thyroid hormones in Chinese pregnant women: A cross-sectional study.

BACKGROUND: Few epidemiological studies have investigated associations of exposure to multiple metals with thyroid hormone homeostasis, especially for the pregnant women. METHODS: Among all the 1644 participants enrolled in Hangzhou Birth Cohort Study (HBCS) at baseline, a total of 915 pregnant women with complete data of interest were analyzed. Eleven metals were measured in blood samples collected around 25 weeks gestation. Serum levels of thyroid hormones including free triiodothyronine (FT3), total triiodothyronine (TT3), free thyroxine (FT4), total thyroxine (TT4) and thyroid-stimulating hormone (TSH) were abstracted from the medical records. Relationships between tertiles of metal levels (setting the lowest tertile as the reference) and percent changes in thyroid hormones were estimated by multivariable adjusted linear regression models. RESULTS: Five metals [arsenic (As), selenium (Se), manganese (Mn), nickel (Ni), antimony (Sb)] were significantly linked to decreased levels of one or more thyroid hormones based on trend tests in the single-metal models. Percent changes [95% confidence intervals (CIs)] in thyroid hormones for the third tertiles of metals remained significant between FT3 and As [-3.53% (-5.48%, -1.54%)]; and between TT3 and As [-4.19% (-7.00%, -1.31%)]; and between FT4 and Mn [-2.05% (-3.49%, -0.58%)], Sb [-1.99% (-3.44%, -0.52%)] in the multiple-metal models. CONCLUSIONS: Thyroid hormone concentrations were reversely related to the levels of blood metals of As, Mn and Sb among Chinese pregnant women. Additional prospective studies are warranted to confirm the causality. Paper capsule: Exposure to multiple metals was reversely associated with one or more thyroid hormones in the Chinese pregnant women.

The Relationship between Type 2 Diabetes and Platelet Indicators.

BACKGROUND: Currently, the studies on the relationship between type 2 diabetes and platelets indicators were carried out on a selective small sample population generally. Large sample studies in this area are rare, especially in Chinese population. In this study, we aimed to investigate the relationship between type 2 diabetes and the mean platelet volume (MPV), platelet count (PLT) and platelet distribution width (PDW). METHODS: This is a cross-sectional analysis of the routine health examination data from 20128 participants with complete baseline data in Yinzhou District 2013. The detection of indicators in this study was completed by automatic hematology analyzer. RESULTS: The PDW and PLT were not significantly different between diabetic group and non-diabetic group, (16.00% vs. 16.00%, P=0.88, and 194*109/L vs. 196*109/L, P=0.05 respectively). The MPV was significantly higher in diabetic group (9.3fl vs. 9.2fl, P<0.05). MPV was an independent risk factor of diabetes mellitus (Unadjusted OR=1.07 (95% CI: 1.03, 1.11), Adjusted for age, sex OR=1.07 (95% CI: 1.02, 1.12)). The adjusted odds ratio of diabetes rose with increasing MPV levels and were most pronounced in subjects with MPV levels exceeding the 90th percentile (MPV ≥10.70 fl, Crude or=1.23 adjusted or=1.19). CONCLUSION: There was no relationship between the presence of diabetes with PDW and PLT. The MPV was independently associated with the presence of diabetes.

Gender disparity in the associations of overweight/obesity with occupational activity, transport to/from work, leisure-time physical activity, and leisure-time spent sitting in working adults: A cross-sectional study.

BACKGROUND: The associations of occupational activity (OA), commuting, leisure-time physical activity (LTPA), and sitting with overweight/obesity in working adults are controversial. This study explored these factors with the risk of overall and abdominal overweight/obesity in a Chinese working population and whether these associations differ by gender. METHODS: A cross-sectional study was conducted. Data analysis was done among 6739 employed participants. Multivariate logistic regression was used to estimate the odds ratios (ORs) and 95% confidence intervals (CIs) for the studied associations. RESULTS: For male employees, those with heavy OA had a lower overall (OR 0.76; 95% CI, 0.62-0.93) and abdominal (OR 0.76; 95% CI, 0.62-0.93) overweight/obesity risk than those with light OA. Those with LTPA ≥150 min/week had a lower risk of overall (OR 0.73; 95% CI, 0.56-0.96) and abdominal (OR 0.70; 95% CI, 0.53-0.91) overweight/obesity than those with LTPA <150 min/week. Men with leisure-sitting time <2.5 h/day had a significantly lower risk of abdominal overweight/obesity than those sitting ≥4 h/day (OR 0.80; 95% CI, 0.65-0.99). And men who cycled to/from work had a lower risk of overall (OR 0.69; 95% CI, 0.53-0.90) and abdominal overweight/obesity (OR 0.71; 95% CI, 0.54-0.92) than passive transports. However, the above significant associations disappeared among female employees. CONCLUSIONS: Heavy OA, cycling to/from work, and LTPA were associated with lower risk of overall or abdominal overweight/obesity in male employees. Reducing leisure sitting time can also help male employees reduce the risk of abdominal overweight/obesity. More research on gender disparity in the risk of overweight and obesity should be done.

The associations between cigarette smoking and health-related behaviors among Chinese school-aged adolescents.

BACKGROUND: Evidence on the interrelations between cigarette smoking and a cluster of lifestyle behaviors is scarce for the Chinese youth population. This study is conducted to identify the associations between cigarette smoking and multiple health-related behaviors in a Chinese sample of adolescents. METHODS: We used data from 2012 Zhejiang Youth Risk Behavior Survey, which is a school-based survey of 19,542 adolescents that assess risk behaviors using a self-reported questionnaire. The interrelations of cigarette smoking with lifestyle behaviors were investigated using logistic regression models. RESULTS: Cigarette smoking was significantly inversely associated with breakfast (AOR = 0.58), vegetables (AOR = 0.81), fruits (AOR = 0.81), milk consumption (AOR = 0.69) and attending physical education classes (AOR = 0.69), while positively associated with soft drinks (AOR = 2.05), fast food consumption (AOR = 1.21), muscle strengthening activity (AOR = 1.67), computer use (AOR = 1.93) and alcohol drinking (AOR = 5.40). CONCLUSIONS: The results suggested that cigarette smoking was associated with a cluster of health-related behaviors in adolescents, which should be considered in health promotion interventions to target multiple health behaviors.

Prenatal cadmium exposure and preterm low birth weight in China.

Early studies have investigated the effect of prenatal cadmium (Cd) exposure on birth outcomes, such as preterm birth and low birth weight, although the results of these studies are inconsistent. The aim of the present study was to investigate the association between prenatal exposure to Cd and the risk of preterm low birth weight (PLBW). A total of 408 mother-infant pairs (102 PLBW cases and 306 pair matched controls) were selected from the participants enrolled in the Healthy Baby Cohort (HBC) study between 2012 and 2014 in Hubei province, China. Concentrations of Cd in maternal urine collected before delivery were measured by inductively coupled plasma mass spectrometry and adjusted by creatinine. A significant association was observed between higher maternal urinary Cd levels and risk of PLBW (adjusted odds ratio (OR)=1.75 for the medium tertile, 95% confidence interval (CI): 0.88, 3.47; adjusted OR=2.51 for the highest tertile, 95% CI: 1.24, 5.07; P trend=0.03). The association was more pronounced among female infants than male infants. Our study suggested that prenatal exposure to Cd at the current level encountered in China may potentially increase the risk of delivering PLBW infants, particularly for female infants.

A nested case-control study of prenatal vanadium exposure and low birthweight.

STUDY QUESTION: Is prenatal vanadium exposure associated with adverse birth outcomes? SUMMARY ANSWER: The odds of low birthweight (LBW) are increased 2.23-fold in mothers with a urinary vanadium of ≥2.91 µg/g creatinine compared with that in mothers with a urinary vanadium of ≤1.42 µg/g creatinine. WHAT IS KNOWN ALREADY: Human exposure to vanadium occurs through intake of food, water and polluted air. Vanadium has been suggested to have fetotoxicity and developmental toxicity in animal studies, and epidemiological studies have reported an association between a decrease in birthweight and vanadium exposure estimated from particulate matter. STUDY DESIGN, SIZE, DURATION: A nested case-control study involving 816 study participants (204 LBW cases and 612 matched controls) was conducted with data from the prospective Healthy Baby Cohort between 2012 and 2014 in the province of Hubei, China. PARTICIPANTS/MATERIALS, SETTING, METHODS: Vanadium concentrations in 816 maternal urine samples collected before delivery [the median gestational age was 39 weeks (range 27-42 weeks)] were measured by inductively coupled plasma mass spectrometry. Information on the infants' birth outcomes was obtained from medical records. Conditional logistic regression was used to calculate the odds ratios (ORs) and 95% confidence intervals (CIs). MAIN RESULTS AND THE ROLE OF CHANCE: The median urinary vanadium concentration of the cases was much higher than that of the controls (3.04 µg/g creatinine versus 1.93 µg/g creatinine). The results revealed a significant positive trend between the odds of LBW and level of maternal urinary vanadium [relative to the lowest tertile; adjusted OR = 1.69 (95% CI: 0.92, 3.10) for the medium tertile; adjusted OR = 2.23 (95% CI: 1.23, 4.05) for the highest tertile; P-trend = 0.02]. Additionally, the association was not modified by maternal age (P for heterogeneity = 0.70) or infant gender (P for heterogeneity = 0.21). LIMITATIONS, REASONS FOR CAUTION: The maternal urine sample was collected before labor, and the maternal urinary vanadium levels measured at one point in time may not accurately reflect the vanadium burden during the entire pregnancy. WIDER IMPLICATIONS OF THE FINDINGS: The results of this study can enrich the biological monitoring data on urinary vanadium in pregnant women; and may be evidence that vanadium may affect fetal development. STUDY FUNDING/COMPETING INTERESTS: This work was supported by the National Natural Science Foundation of China (21437002, 81372959 and 81402649), the R&D Special Fund for Public Welfare Industry (Environment) (201309048) and the Fundamental Research Funds for the Central Universities, HUST (2016YXZD043). The authors have no conflicts of interest to declare.

A case-control study of maternal exposure to chromium and infant low birth weight in China.

Exposure to chromium is increasing due to environmental pollution from industrial processes. Several epidemiological studies have investigated chromium exposure and reproductive outcomes, but few studies have investigated the association of chromium exposure and low birth weight (LBW). This study was designed to investigate whether maternal exposure to chromium during pregnancy is associated with an increased risk of LBW. Chromium concentrations in maternal urine samples collected at delivery were measured in 204 LBW cases and 612 matched controls recruited between 2012 and 2014 in Hubei Province, China. Risk of LBW was associated with higher levels of chromium in maternal urine [adjusted odds ratio (OR) = 1.77 for the medium tertile, 95% confidence interval (CI): 0.95, 3.29; adjusted OR = 2.48 for the highest tertile, 95% CI: 1.33, 4.61; P trend = 0.01]. The association was more pronounced among female infants (adjusted OR = 3.67 for the highest tertile, 95% CI: 1.50, 8.97) than among male infants (adjusted OR = 1.22 for the highest tertile, 95% CI = 0.48, 3.11) (p heterogeneity = 0.06). Our findings suggest that maternal exposure to higher levels of chromium during pregnancy may potentially increase the risk of delivering LBW infants, particularly for female infants.

A Case-Control Study of Prenatal Thallium Exposure and Low Birth Weight in China.

BACKGROUND: Thallium (Tl) is a highly toxic heavy metal widely present in the environment. Case reports have suggested that maternal exposure to high levels of Tl during pregnancy is associated with low birth weight (LBW), but epidemiological data are limited. OBJECTIVES: This study was designed to evaluate whether prenatal Tl exposure is associated with an increased risk of LBW. METHODS: This case-control study involving 816 study participants (204 LBW cases and 612 matched controls) was conducted in Hubei Province, China, in 2012-2014. Tl concentrations were measured in maternal urine collected at delivery, and associations with LBW were evaluated using conditional logistic regression. RESULTS: Higher maternal urinary Tl levels were significantly associated with increased risk of LBW [crude odds ratio (OR) = 1.52; 95% CI: 1.00, 2.30 for the highest vs. lowest tertile], and the association was similarly elevated after adjustment for potential confounders (adjusted OR = 1.90; 95% CI: 1.01, 3.58 for the highest vs. lowest tertile). Stratified analyses showed slightly higher risk estimates for LBW associated with higher Tl levels for mothers < 28 years old and for mothers with lower household income; however, there was no statistical evidence of heterogeneity in risk according to maternal age (p for heterogeneity = 0.18) or household income (p for heterogeneity = 0.28). CONCLUSION: To our knowledge, ours is the first case-control study to investigate the association between prenatal Tl exposure and LBW. The results suggest that prenatal exposure to high levels of Tl may be associated with an increased risk of LBW. CITATION: Xia W, Du X, Zheng T, Zhang B, Li Y, Bassig BA, Zhou A, Wang Y, Xiong C, Li Z, Yao Y, Hu J, Zhou Y, Liu J, Xue W, Ma Y, Pan X, Peng Y, Xu S. 2016. A case-control study of prenatal thallium exposure and low birth weight in China. Environ Health Perspect 124:164-169; http://dx.doi.org/10.1289/ehp.1409202.

Prenatal exposure to lead in relation to risk of preterm low birth weight: A matched case-control study in China.

We investigated the association between prenatal exposure to lead (Pb) and the risk of preterm low birth weight (PLBW). Pb concentrations in maternal urine collected at birth from 408 subjects (102 cases and 306 matched controls) were analyzed and adjusted by creatinine. The median Pb concentration in the PLBW cases (10.60µgPb/g creatinine) was higher than that of the controls (7.28µgPb/g creatinine). An adjusted odds ratio (OR) of 2.96 (95% CI=1.49-5.87) for PLBW was observed when the highest tertile was compared to the lowest tertile of Pb levels. The association was more pronounced among female infants (adjusted OR=3.67 for the highest tertile; 95% CI=1.35-9.93) than male infants (adjusted OR=1.91 for the highest tertile; 95% CI=0.74-4.95). Our study suggests that prenatal exposure to levels of Pb encountered today in China is associated with an elevated risk of PLBW.