Work engagement and associated factors among Japanese registered dietitians and dietitians: a cross-sectional study.

Healthcare services provided by registered dietitians and dietitians have been changing because of evolving lifestyles and population dynamics, leading to subsequent changes in the occupational status and experiences of these professionals. However, few studies have examined occupational stress among registered dietitians and dietitians. This study involved a cross-sectional survey to investigate the status and associated factors of work engagement among registered dietitians and dietitians, whose professions differ based on licensing processes and scope of work. A total of 3,593 questionnaires were distributed, 1,890 responses were received, and 1,654 valid questionnaires were analyzed. Work engagement was measured using the Utrecht Work Engagement Scale. Multiple regression analysis was conducted to examine the associations between work engagement and each factor. The work engagement scores of dietitians were significantly lower than those of registered dietitians. Further, work engagement was associated with age, workplace, coworker support, and effort-reward ratio for both registered dietitians and dietitians. However, exercise habit was a significant factor associated with work engagement only among dietitians. Work engagement among registered dietitians was comparable to that of typical Japanese workers, whereas it was lower among dietitians. The findings highlight the importance of considering associated factors to improve work engagement further, especially among dietitians.

A cross-sectional study of the association between effort-reward imbalance and psychologic distress among Japanese dietitians.

OBJECTIVES: This study aims to clarify dietitians' effort-reward imbalance (ERI) and examine its association with psychologic distress. METHODS: A cross-sectional survey was conducted. A total of 3593 questionnaires were distributed to dietitians in about 110 organizations and 1890 responses were received (response rate 52.6%). Hence, a total of 1743 valid questionnaires were used in the analysis. Effort-reward (ER) ratio was measured by a subscale of the ERI Questionnaire, and psychologic distress was measured by the Kessler Psychological Distress Scale (K6). The association between the ER ratio and psychologic distress was analyzed by multiple logistic regression analysis with covariates. RESULTS: The mean ER ratio was 0.83 (SD = 0.53) and ERI (ER ratio >1) prevalence was 26.3%. The mean K6 score was 7.1 (5.3), and psychologic distress (K6 score ≥5) prevalence was 62.4%. The increased psychologic distress was associated with a higher ER ratio, less support from supervisors and coworkers, and lower age and household income. ERI was significantly associated with psychologic distress, even after being adjusted for covariates. CONCLUSIONS: Dietitians experience high stress, as shown by their high ER ratio and K6 scores. Their ERI was greatly associated with psychologic distress.

Psychological distress and associated factors among Japanese nursery school and kindergarten teachers: a cross-sectional study.

The understaffing of nursery schools and kindergartens and the increasing workload of childcare workers are becoming significant issues in Japan. In this study, a cross-sectional survey was conducted to investigate the stress experienced by childcare workers and its antecedents. We distributed 2,640 questionnaires to childcare workers in Miyagi prefecture, obtaining a response rate of 51.9% (n=1,370). Finally, 1,210 valid questionnaires were used in the analysis. As a stress indicator, psychological distress was measured with the Kessler Screening Scale for Psychological Distress (K6). The mean K6 score was 7.0 (SD=5.4), and the prevalence of psychological distress (K6 score ≥5) was 60.0%. Considering work-related factors, the mean scores were as follows: supervisor support 11.8 (2.6), coworker support 12.1 (2.0), work engagement 3.2 (1.2), and effort-reward ratio 0.93 (0.53). A multivariate logistic regression analysis with adjustment for possible confounders revealed that increased psychological distress was associated with higher effort-reward ratio, lower support from supervisors and coworkers, lower work engagement, and insufficient sleep. These results suggest that elevated psychological distress is strongly associated with effort-reward imbalance, while high work engagement in childcare workers helped to reduce their distress.

Exposure profile of mercury, lead, cadmium, arsenic, antimony, copper, selenium and zinc in maternal blood, cord blood and placenta: the Tohoku Study of Child Development in Japan.

BACKGROUND: The effects of prenatal exposure to toxic elements on birth outcomes and child development have been an area of concern. This study aimed to assess the profile of prenatal exposure to toxic elements, arsenic (As), bismuth (Bi), cadmium (Cd), mercury (total mercury (THg), methylmercury (MHg), inorganic mercury (IHg)), lead (Pb), antimony (Sb) and tin (Sn), and essential trace elements, copper (Cu), selenium (Se) and zinc (Zn), using the maternal blood, cord blood and placenta in the Tohoku Study of Child Development of Japan (N = 594-650). METHODS: Inductively coupled plasma mass spectrometry was used to determine the concentrations of these elements (except mercury). Levels of THg and MeHg were measured using cold vapour atomic absorption spectrophotometry and a gas chromatograph-electron capture detector, respectively. RESULTS: Median concentrations (25th-75th) of As, Cd, Pb, Sb, Sn and THg in the maternal blood were 4.06 (2.68-6.81), 1.18 (0.74-1.79), 10.8 (8.65-13.5), 0.2 (0.06-0.40) and 0.2 (0.1-0.38) ng mL-1 and 5.42 (3.89-7.59) ng g-1, respectively. Median concentrations (25th-75th) of As, Cd, Pb, Sb, Sn and THg in the cord blood were 3.68 (2.58-5.25), 0.53 (0.10-1.25), 9.89 (8.02-12.5), 0.39 (0.06-0.92) and 0.2 (0.2-0.38) ng mL-1 and 9.96 (7.05-13.8) ng g-1, respectively. CONCLUSIONS: THg and Sb levels in the cord blood were twofold higher than those in the maternal blood. Cord blood to maternal blood ratios for As, Cd and Sb widely varied between individuals. To understand the effects of prenatal exposure, further research regarding the variations of placental transfer of elements is necessary.

Psychomotor Ability in Children Prenatally Exposed to Methylmercury: The 18-Month Follow-Up of Tohoku Study of Child Development.

Fish contain nutrients essential to the developing fetal brain, but they are contaminated with methylmercury. The Tohoku Study of Child Development, now underway in the Sanriku coastal area of Miyagi prefecture, Japan, follows mother-child pairs to examine the risks and benefits of fish consumption during pregnancy, especially the effects of prenatal exposures to methylmercury, selenium, and docosahexaenoic acid (DHA) on child neurodevelopment. Children aged 18 months were administered the Bayley Scales of Infant Development second edition (BSID-II) and Kyoto Scale of Psychological Development (KSPD) in 2004-2008. Complete data of cord-blood total mercury (THg), cord-plasma selenium, maternal-plasma DHA, the above test scores, and confounders for 566 mother-child pairs were available. The median cord-blood THg level was 15.7 (range, 2.7-96.1) ng/g. Since the BSID-II and KSPD scores were significantly lower in the 285 boys than in the 281 girls, analyses were conducted separately. The Psychomotor Development Index (PDI) of BSID-II was significantly correlated with cord-blood THg only in the boys, and significance of the association remained unchanged after adjusting for possible confounders; i.e., a 10-fold increase in cord-blood THg was associated with a 8.3-point decrease in the score of the PDI. Other significant correlations of THg were not seen in the boys or girls. Selenium and DHA showed no significant correlations with the BSID-II or KSPD scores in either sex. In conclusion, intrauterine methylmercury exposure may affect psychomotor development, and boys appear to be more vulnerable to the exposure than girls.

Recent Epidemiological Studies on Methylmercury, Mercury and Selenium.

More than sixty years has passed since the outbreak of Minamata disease, and high-level methylmercury contaminations now seem nonexistent in Japan. However, mercury has been continuously discharged from natural sources and industrial activities, and the health effects on children susceptible to methylmercury exposure at low levels, in addition to mercury contamination from mercury or gold mining areas in developing countries, become a worldwide concern. In this article, we provide a recent overview of epidemiological studies regarding methylmercury and mercury. The following findings were obtained. (1) Many papers on exposure assessment of methylmercury/mercury have been published since the Minamata Convention on Mercury was adopted in 2013. (2) The most crucial problem is child developmental neurotoxicity resulting from prenatal exposure to methylmercury, but its precise assessment seems to be difficult because most of such effects are neither severe nor specific. (3) Several problems raised in birth cohort studies (e.g., whether IQ deficits due to prenatal methylmercury exposure remain when the children become adults, or whether the postnatal exposure at low levels also causes such adverse effects in children) remain unsolved. (4) Concurrent exposure models of methylmercury, lead, polychlorinated biphenyls, aresenic, and organochlorine pesticides, as well as possible antagonists such as polyunsaturated fatty acids and selenium, should be considered in the study design because the exposure levels of methylmercury are extremely low in developed countries. (5) Further animal experiments and molecular biological studies, in addition to human studies, are required to clarify the mechanism of methylmercury toxicity.

High iodine intake by preschool children in Miyagi prefecture, Japan.

OBJECTIVES: Standard Tables of Food Composition in Japan 2010 (FCT) remain incomplete for iodine contents. This survey was initiated to develop a method to cope with this shortage and to find daily iodine intake of preschool children in Japan. METHODS: Data were available for one-day food intake for 296 3- to 6-year-old children (the total cases). 128 samples (the selected cases) were analyzed by ICP-MS for iodine (the measured values). Iodine intake was also calculated using FCT assuming that iodine contents in missing items were zero (the calculated values). RESULTS: Measured and calculated values for the selected 125 cases (after exclusion of 3 extreme cases) gave geometric means (GM) of 117.6 and 101.8 µg/day. The measured/calculated ratio in GM, 117.6/101.8 = 1.155, was applied to the calculated values for total 296 cases to estimate iodine intake (the estimated values). GM for the estimated value was 175.2 µg/day and it was 8.93 µg/kg/day after adjustment for body weight for 296 children. There was no significant difference between boys and girls. DISCUSSION: The GM values for both the measured and estimated values (n = 125 pairs) were 117.6 µg/day. The agreement suggested that the factor employed, 1.155, was proper and adequate. Literature survey suggested that values on a body weight basis were comparable between the children and adults in Japan. The levels were higher than levels in east Asian countries. CONCLUSIONS: A correction method was developed for estimation of daily dietary iodine intake. The iodine intake level for preschoolers was comparable to levels for adult population.

Applicability of food composition tables as a tool to estimate mineral and trace element intake of pre-school children in Japan: a validation study.

Because dietary intakes of some minerals (including trace elements), especially iron (Fe), are insufficient for the needs of the general Japanese population, accurate estimation of mineral intake is important. This capability is especially necessary to preserve the health of Japanese children. Therefore, the current version of food composition tables (FCT) in Japan was evaluated for validity as tools to estimate dietary intake of minerals for children. For this purpose, 24h food duplicate samples were collected from 292 pre-school children in Miyagi prefecture, Japan. From the weights of items and food codes, intakes of nine minerals were estimated taking advantage of the FCT. In parallel, amounts of minerals in each duplicate samples were instrumentally measured by ICP-AES for Ca, Cu, Fe, Mg, Mn, P and Zn, and by flame AAS for K and Na, both after wet-ashing. The distributions of the mineral amounts were essentially normal. The comparison of the FCT-based estimates (E) and instrumental measures (M) showed that the E/M ratio was close to 1 for Ca, K, Mn, P and Zn, suggesting that E may be a surrogate of M for Ca, K, Mn, P and Zn on a group basis. The ratio being larger than 1.2 for Cu, Fe, Mg and Na indicates that a risk of over-estimation exists when E is relied upon in place of M. On an individual basis, significant differences were detected for all 9 minerals suggesting that the use of E as a surrogate for M should be practiced with care for the estimation of mineral intake.

Dietary tin intake and association with canned food consumption in Japanese preschool children.

OBJECTIVES: Dietary intake of tin has seldom been studied in children although they probably have a high intake. This study was initiated to investigate dietary tin intake (Sn-D) of children in Japan. METHODS: In this study, 24-h food duplicate samples were collected from 296 preschool children in Miyagi prefecture, Japan. Sn in the samples were analyzed by inductively coupled-plasma mass spectrometry, after homogenization and wet digestion. RESULTS: Sn-D by the children was low, with 4.2 µg/day as a median. The distribution was however wide, from 0.4 µg/day up to >3 µg/day. Canned foods were the major dietary Sn source, whereas rice contributed essentially little. Sn-D among canned food consumers was 30.2 µg/day as a geometric mean (10.6 µg/day as a median), whereas Sn-D among the non-consumers of canned foods was distributed log-normally, with 3.3 µg/day as a geometric mean (2.5 µg/day as a median). Sn levels in urine did not differ between children who consumed canned foods on the day previous to urine collection and those who did not. The Sn-D was far below the provisional tolerable weekly intake (14 mg/kg body weight/week) set by the 2001 Joint FAO/WHO Expert Committee. Nevertheless, children took more Sn than adults when compared on a body-weight basis. CONCLUSIONS: Canned foods were the major source of dietary Sn intake for preschool children studied. Thus, median Sn-D was higher for the canned food consumers (10.6 µg/day) than for non-consumers of canned foods (2.5 µg/day). Sn-D by canned food-consuming children was, however, substantially lower than the provisional tolerable weekly intake. No difference was detected in Sn levels in urine between canned food-consuming and non-consuming children.

High cadmium and low lead exposure of children in Japan.

BACKGROUND: Cadmium (Cd) is a wide-spread environmental pollutant with insidious toxicity to kidneys, and children are considered to be a high-risk group. Lead (Pb) is suspected to induce retardation in mental development in children. Daily foods are an important source of both Cd and Pb exposure for general population. Nevertheless, data on dietary exposure of children to Cd and Pb are still scarce in Japan. OBJECTIVES: This study was initiated to clarify the extent of exposure of children to Cd. Exposure to Pb, another environmental pollutant element, was also studied in combination. METHODS: Twenty-four-hour food duplicates and the first morning urine samples were collected from 296 children (159 boys and 137 girls at the ages of 3-6 years) in 15 kindergartens in Miyagi prefecture on the Pacific coast in north-east Japan; no environmental pollution with Cd has been known in the prefecture. Cd, Pb and iron in food duplicates and Cd in urine were analyzed by inductively coupled plasma-mass spectrometry. α(1)-Microglobulin (α(1)-MG) in urine was measured by the latex method. Log-normal distributions were confirmed for these analytes. RESULTS: The geometric mean (GM) values for dietary intake of Cd and Pb were 11.8 and 2.28 µg/day, or 4.20 and 0.84 µg/kg body weight/week, respectively, for total children studied. No significant difference was detected in dietary Cd and Pb intake between boys and girls of the same age (except for Pb on a µg/day basis at 6 years) as well as of all ages in combination. Trends of increase in Cd and Pb intake were observed parallel to age when calculated on a daily intake basis, but the trends disappeared after correction for body weight. No age-dependent increase was observed in α(1)-MG, despite there was an age-dependent increase in Cd. CONCLUSIONS: The dietary intake of Cd and Pb for children studied were 4.20 and 0.84 µg/kg body weight/week, respectively. International comparison of the present results with values reported in literature suggested that exposure of children in Japan was higher with regard to Cd, and lower regarding Pb, reproducing the observation in adult Japanese populations. For better health of children, efforts may be necessary to reduce high dietary exposure to Cd.

Prenatal exposures to environmental chemicals and birth order as risk factors for child behavior problems.

OBJECTIVES: To assess whether polychlorinated biphenyls (PCBs), methylmercury, lead, or parental child-rearing attitudes was most crucial for maladaptive behavior problems, we examined Japanese 30-month-old children followed up from pregnancy. METHODS: The Child Behavior Checklist (CBCL) was used to assess the behavior problems in 306 children. The associations of cord-blood total PCBs (ΣPCB), total mercury (THg), and lead with each CBCL subscale were examined by multivariate analyses. RESULTS: The median values in cord blood of the 306 children were 48.3 (5 and 95 percentiles, 18.6-116.3) ng/g-lipid for ΣPCB, 10.2 (4.1-24.5)ng/g for THg, and 1.0 (0.5-1.7)µg/dl for lead. The internalizing score of the CBCL was significantly correlated with ΣPCB (r=0.113) in the children, though no significant correlation was seen between any CBCL score and either THg or lead. The significant correlation disappeared when conducting multiple regression analysis with possible confounders; at that time, the birth order, home environment, and maternal intelligence quotient were significantly related to the internalizing score. Three CBCL scores and ΣPCB levels were significantly higher in the first-born children than in the second-born or following children, and the partial correlation coefficient with the adjustment for all confounders except birth order was significant between the internalizing score and ΣPCB in the latter children (r=0.175). CONCLUSIONS: Internalizing behavior appears to be affected by prenatal exposure to PCBs at low levels. Under lower-level exposures, however, behavior problems may be more strongly associated with parental child-rearing attitudes involved in birth order, than with such hazardous chemicals.

Hair-to-blood ratio and biological half-life of mercury: experimental study of methylmercury exposure through fish consumption in humans.

The hair-to-blood ratio and biological half-life of methylmercury in a one-compartment model seem to differ between past and recent studies. To reevaluate them, 27 healthy volunteers were exposed to methylmercury at the provisional tolerable weekly intake (3.4 µg/kg body weight/week) for adults through fish consumption for 14 weeks, followed by a 15-week washout period after the cessation of exposure. Blood was collected every 1 or 2 weeks, and hair was cut every 4 weeks. Total mercury (T-Hg) concentrations were analyzed in blood and hair. The T-Hg levels of blood and hair changed with time (p < 0.001). The mean concentrations increased from 6.7 ng/g at week 0 to 26.9 ng/g at week 14 in blood, and from 2.3 to 8.8 µg/g in hair. The mean hair-to-blood ratio after the adjustment for the time lag from blood to hair was 344 ± 54 (S.D.) for the entire period. The half-lives of T-Hg were calculated from raw data to be 94 ± 23 days for blood and 102 ± 31 days for hair, but the half-lives recalculated after subtracting the background levels from the raw data were 57 ± 18 and 64 ± 22 days, respectively. In conclusion, the hair-to-blood ratio of methylmercury, based on past studies, appears to be underestimated in light of recent studies. The crude half-life may be preferred rather than the recalculated one because of the practicability and uncertainties of the background level, though the latter half-life may approximate the conventional one.

Recent evidence from epidemiological studies on methylmercury toxicity.

More than fifty years have passed since the outbreak of Minamata disease, and large-scale methylmercury poisoning due to industrial effluents or methylmercury-containing fungicide intoxication has scarcely happened in developed countries. On the other hand, widespread environmental mercury contamination has occurred in gold and mercury mining areas of developing countries. In this article, we provided an overview of recent studies addressing human health effects of methylmercury, which we searched using the PubMed of the US National Library of Medicine. The following suggestions were obtained for low-level methylmercury exposure: (1) In recent years, the proportion of human studies addressing methylmercury has tended to decrease. (2) Prenatal exposure to methylmercury through fish intake, even at low levels, adversely affects child development after adjusting for polychlorinated biphenyls and maternal fish intake during pregnancy, whereas maternal seafood intake has some benefits. (3) Long-term methylmercury exposure through consumption of fish such as bigeye tuna and swordfish may pose a potential risk of cardiac events involving sympathovagal imbalance. (4) In measuring methylmercury levels in preserved umbilical cord collected from inhabitants born in Minamata areas between 1945 and 1989, the elevated concentrations (≥1 mg/g) were observed mainly in inhabitants born between 1947 and 1968, and the peak coincided with the peak of acetaldehyde production in Minamata. (5) Since some developing countries appear to be in similar situations to Japan in the past, attention should be directed toward early recognition of a risky agent and precautions should be taken against it.

Intervention study on cardiac autonomic nervous effects of methylmercury from seafood.

To scrutinize whether the provisional tolerable weekly intake (PTWI, 3.4 microg/kg body weight/week) of methylmercury in Japan is safe for adults, we conducted an intervention study using heart rate variability (HRV) that has been considered to reflect cardiac events. Fifty-four healthy volunteers were recruited and divided into experimental and control groups. The experimental group was exposed to methylmercury at the PTWI level through consumption of bigeye tuna and swordfish for 14 weeks, and HRV parameters were compared between the two groups. In the experimental group, mean hair mercury levels, determined before and after the dietary methylmercury exposure and after 15-week wash-out period following the cessation of exposure, were 2.30, 8.76 and 4.90 microg/g, respectively. The sympathovagal balance index of HRV was significantly elevated after the exposure, and decreased to the baseline level at the end of this study. Still, such changes in HRV parameters were not found in the control group with a mean hair mercury level of around 2.1 microg/g. In conclusion, the PTWI does not appear to be safe for adult health, because methylmercury exposure from fish consumption induced a temporary sympathodominant state. Rather, long-term exposure to methylmercury may pose a potential risk for cardiac events involving sympathovagal imbalance among fish-consuming populations.

Gene expression profiles in the brain of the neonate mouse perinatally exposed to methylmercury and/or polychlorinated biphenyls.

Methylmercury (MeHg) and polychlorinated biphenyls (PCBs) are environmentally persistent neurodevelopmental toxicants. The primary source of human exposure is the consumption of contaminated fish, seafood and marine mammals. However, little is known about the molecular mechanisms of MeHg and PCB toxicities and interactions between these contaminants. We investigated the functional profiles of differently expressed genes in the brains of offspring mice perinatally exposed to MeHg and/or PCBs to elucidate how these contaminants interact with each other. Pregnant mice (C57BL/6) were divided into four groups by exposure: (1) vehicle control, (2) MeHg alone, (3) PCBs alone, (4) MeHg + PCBs. Gene expression analysis of the brains of offspring mice was carried out with 4 x 44 K whole mouse genome's microarrays (Agilent) on postnatal day 1. The gene expression pattern of the MeHg exposure-group differed from that of the PCB-exposure group. The MeHg + PCB group expressed a larger number of genes, most of which were not expressed in the MeHg group or PCB group. It was revealed that gene expression was greatly increased, and the most altered genes were found with co-exposure. The genes were related to the functional categories of development, inflammation, calcium ion homeostasis, signal transduction, the ubiquitin-proteasome pathway and detoxication. The ubiquitin-proteasome system and detoxication categories might function for protection against the toxicity induced by co-exposure to MeHg and PCBs. These results suggest that co-exposure does not simply exacerbate the toxicity of MeHg alone or PCB alone, but stimulates a protection system.

Assessment of exposure to methylmercury in pregnant Japanese women by FFQ.

OBJECTIVE: To examine whether an FFQ can be used for assessing exposure to methylmercury (MeHg) by estimating MeHg intake from seafood consumption using the FFQ and confirming the accuracy of the estimated value. DESIGN: Seafood consumption of pregnant women was assessed using the FFQ. Total mercury (T-Hg) concentrations of maternal red blood cells (RBC) and hair were measured as exposure indices of MeHg. SETTING: A prospective birth cohort study, the Tohoku Study of Child Development (TSCD), which has been ongoing since 2001. SUBJECTS: The subjects were 609 pregnant Japanese women who were enrolled in the TSCD. RESULTS: MeHg intake was estimated from seafood consumption determined using the FFQ and the MeHg concentrations in each type of seafood. The accuracy of the estimated value was confirmed by comparison with T-Hg in RBC and hair. Estimated MeHg intake was 42.3 microg/week, and 43.0 % of that was from large predatory fish. Compared with the Japanese tolerable weekly intake, in total 12.5 % of the subjects exceeded it. T-Hg concentrations in RBC and hair were significantly correlated with estimated MeHg intake: r = 0.325 (P < 0.0001) for RBC and r = 0.305 (P < 0.0001) for hair. CONCLUSIONS: Estimated MeHg intake based on the FFQ was significantly associated with T-Hg concentrations in RBC and hair. Although the estimated value involves uncertainties, the FFQ appears to be a useful tool for assessment of exposure to MeHg.