Multiple classes of environmental chemicals are associated with liver disease: NHANES 2003-2004

Biomonitoring studies show that humans carry a body burden of multiple classes of contaminants which are not often studied together. Many of these chemicals may be hepatotoxic. We used the 2003-2004 National Health and Nutrition Examination Survey to evaluate the relationship between alanine aminotransferase (ALT) and 37 environmental contaminants, comprising heavy metals, non-dioxin-like polychlorinated biphenyls (PCBs), and dioxin-like compounds, using a novel method. Linear regression models were constructed for each chemical separately, then as a class, using quartiles to represent exposure and adjusting for age, sex, race, income, and BMI. We then used an optimization approach to compile a weighted sum of the quartile scores, both within and across chemical classes. Using the optimization approach to construct weighted quartile scores, the dioxin like PCB, the non-dioxin like PCB and metal class-level scores were significantly associated with elevated ALT. A significant interaction was detected between the class-level score for metals, and the score for non-dioxin-like PCBs. When including all chemicals in one model, 3 chemicals accounted for 78% of the weight (mercury, PCB 180, 3,3',4,4',5-PNCB) with the remaining 22% associated with 4 chemicals (a dioxin and 3 PCBs). Validation with a holdout dataset indicated that the weighted quartile sum estimator efficiently identifies reproducible significant associations.

The contribution of diet to total bisphenol A body burden in humans: results of a 48 hour fasting study

Human biomonitoring studies measuring bisphenol A (BPA) in urine have shown widespread exposure in the general population. Diet is thought to be a major route of exposure. We studied urinary BPA patterns in five individuals over a 48-h period of fasting (bottled water only). Personal activity patterns were recorded with a diary to investigate non-dietary routes of exposure. All urine void events during the fast were collected, as well as events before and after the fast. The pattern of BPA concentrations was similar for all participants: they rose near the beginning of the fast (after the pre-fast meal), declined over the next 24h, fluctuated at lower levels during the second day, and then rose after the post-fast meal. Concentrations (~2 μg/g creatine) and calculated BPA intakes (~0.03 μg/kg-day) in these individuals during the first 24h were consistent with general population exposures. For the second 24h, concentrations and intakes declined by about two-thirds. One of the individuals had an extraordinary pre-fast exposure event with concentrations rising as high as 98 μg/g creatine but declining to <5 μg/g creatine by day 2. Given patterns found in day 1 and the subsequent decline to lower levels in day 2, we hypothesize that BPA exposures in these individuals were diet-driven. No events in the diary (use of personal care products, e.g.) appear associated with exposures. On day 2, non-dietary sources may still be present, such as from dust. Another hypothesis is that small reservoirs of BPA from past exposures are released from storage (lipid reservoirs, e.g.) and excreted.

Population variability of phthalate metabolites and bisphenol A concentrations in spot urine samples versus 24- or 48-h collections

Human exposure to phthalates and bisphenol A (BPA) can be assessed through urinary biomonitoring, but methods to infer daily intakes assume that spot sample concentrations are comparable to daily average concentrations. We evaluate this assumption using human biomonitoring data from Germany and the United States (US). The German data comprised three regional studies with spot samples and one with full-day samples analyzed for phthalate metabolites. The US data included: a study on DEHP metabolites and BPA involving eight persons supplying all urine voids (from which 24-h samples were constructed) for seven consecutive days; NHANES spot sample data on DEHP metabolites and BPA; and a regional study of children with 48-h samples analyzed for BPA. In the German data, measures of central tendency differed, but spot and 24-h samples showed generally comparable variance including 95th percentiles and maxima equidistant from central tendency measures. In contrast, the US adult data from the eight-person study showed similar central tendencies for phthalate metabolites and BPA, but generally greater variability for the spot samples, including higher 95th percentiles and maxima. When comparing children's BPA concentrations in NHANES spot and 48-h samples, distributions showed similar central tendency and variability. Overall, spot urinary concentrations of DEHP metabolites and BPA have variability roughly comparable with corresponding 24-h average concentrations obtained from a comparable population, suggesting that spot samples can be used to characterize population distributions of intakes. However, the analysis also suggests that caution should be exercised when interpreting the high end of spot sample data sets.

Metals in blood and urine, and thyroid function among adults in the United States 2007-2008

The thyroid is integral to regulation of development and metabolism. Certain metals have been shown to affect thyroid function in occupationally exposed persons, but few studies have been conducted in the general population. This study evaluates the association between biomarkers of metal exposure and thyroid hormones in the US population. Analyses included adults participating in the 2007-2008 National Health and Nutrition Examination Survey, with no history of thyroid disease or use of thyroid medications, and with data on metals in blood (lead, cadmium and mercury) and urine (lead, cadmium, mercury, barium, cobalt, cesium, molybdenum, antimony, thallium, tungsten and uranium), and thyroid hormones (TSH, free and total T3 and T4) in serum (N=1587). Multivariate linear regression was used to model the association between thyroid hormone levels, and metals in either urine (creatinine-adjusted) or blood. Metal concentrations were considered as both continuous and categorical variables. Models were adjusted for: age, sex, race, BMI, serum lipids, serum cotinine, pregnancy and menopausal status, and use of selected medications. Few participants (<5%) had free T3, free T4, or TSH levels outside the reference range. However, 9.2% (SE=1.2%) had low T3 and 9.4% (SE=1.1%) had low T4. Metals were detected in nearly all blood and urine samples, with the highest levels seen for urinary molybdenum (median 42.5μg/L). When including all blood metals, mercury was associated with decreases in T3 and T4, while cadmium was associated with decreased TSH. Urinary cadmium was associated with increases in both T3 and T4 (models including all metals measured in urine). Urinary thallium and barium were associated with decreased T4 (both) and T3 (barium). For TSH, cesium was associated with decreased, and tungsten with increased levels. Given the high prevalence of exposure to metals, associations of the size reported here could indicate an appreciable contribution of metals exposure to the prevalence of thyroid disorders. These findings indicate the importance of further research to further examine these relationships.

A methodological approach to assessing the health impact of environmental chemical mixtures: PCBs and hypertension in the National Health and Nutrition Examination Survey

We describe an approach to examine the association between exposure to chemical mixtures and a health outcome, using as our case study polychlorinated biphenyls (PCBs) and hypertension. The association between serum PCB and hypertension among participants in the 1999–2004 National Health and Nutrition Examination Survey was examined. First, unconditional multivariate logistic regression was used to estimate odds ratios and associated 95% confidence intervals. Next, correlation and multicollinearity among PCB congeners was evaluated, and clustering analyses performed to determine groups of related congeners. Finally, a weighted sum was constructed to represent the relative importance of each congener in relation to hypertension risk. PCB serum concentrations varied by demographic characteristics, and were on average higher among those with hypertension. Logistic regression results showed mixed findings by congener and class. Further analyses identified groupings of correlated PCBs. Using a weighted sum approach to equalize different ranges and potencies, PCBs 66, 101, 118, 128 and 187 were significantly associated with increased risk of hypertension. Epidemiologic data were used to demonstrate an approach to evaluating the association between a complex environmental exposure and health outcome. The complexity of analyzing a large number of related exposures, where each may have different potency and range, are addressed in the context of the association between hypertension risk and exposure to PCBs.

Trends in hospitalizations for peptic ulcer disease, United States, 1998-2005

Infection with Helicobacter pylori increases the risk for peptic ulcer disease (PUD) and its complications. To determine whether hospitalization rates for PUD have declined since antimicrobial drugs to eradicate H. pylori became available, we examined 1998-2005 hospitalization records (using the Nationwide Inpatient Sample) in which the primary discharge diagnosis was PUD. Hospitalizations for which the diagnosis was H. pylori infection were also considered. The age-adjusted hospitalization rate for PUD decreased 21% from 71.1/100,000 population (95% confidence interval [CI] 68.9-73.4) in 1998 to 56.5/100,000 in 2005 (95% CI 54.6-58.3). The hospitalization rate for PUD was highest for adults > or =65 years of age and was higher for men than for women. The age-adjusted rate was lowest for whites and declined for all racial/ethnic groups, except Hispanics. The age-adjusted H. pylori hospitalization rate also decreased. The decrease in PUD hospitalization rates suggests that the incidence of complications caused by H. pylori infection has declined.

Progressive multifocal leukoencephalopathy deaths in the USA, 1979-2005

BACKGROUND

Progressive multifocal leukoencephalopathy (PML) is a neurological disease most often seen among immunosuppressed patients. The incidence of PML increased with an increasing incidence of HIV/AIDS. We describe recent trends and the epidemiology of PML-associated death in the era of highly active antiretroviral therapy (HAART).

METHODS

National multiple-cause-of-death data for the USA were used to identify records with PML listed as a cause of death during 1979-2005. Age-adjusted PML-associated death rates were calculated overall and by sex, race, region and HIV status.

RESULTS

The PML-associated death rates peaked in the mid-1990s and decreased from 2.76 deaths per 1 million persons in 1992-1995 to 0.66 in 2002-2005. This decrease was mainly due to a decreasing death rate among PML decedents with HIV diagnosis, males and those aged 20-49 years at death. A decline in death rate was also seen among PML decedents without HIV diagnosis, although this trend was not significant. Decedents in the latter time period were more often female, and older. The proportion of HIV-associated deaths from PML decreased between 1992-1995 (1.4%) and 2002-2005 (1.0%).

CONCLUSION

PML mortality has decreased significantly since 1996 when HAART became the standard of care in the USA. This decline likely reflects increased survival among HIV-positive persons who receive HAART.

Infectious disease hospitalizations in the United States

BACKGROUND

Infectious diseases (IDs) cause widespread morbidity and mortality. We describe the epidemiology of ID hospitalizations in the United States with use of a nationally representative database.

METHODS

First-listed ID hospitalizations in the United States were analyzed using the Nationwide Inpatient Sample for 1998-2006. Hospitalization rates were calculated overall for IDs and for specific ID groups.

RESULTS

An estimated 40,085,978 (standard error, 255,418) hospitalizations with a first-listed ID occurred during 1998-2006, for an age-adjusted hospitalization rate of 154.4 (95% confidence interval, 153.3-155.5) hospitalizations per 10,000 persons. The rate increased slightly over the study period (152.5 [95% confidence interval, 149.6-155.4] in 1998 vs 162.2 [95% confidence interval, 158.7-165.5] in 2006); an increase was seen for both sexes, for older patients, and for Hispanic patients. Among those aged 5-39 years, female patients had a significantly higher hospitalization rate than did male patients; male patients had higher rates among the youngest children and adults aged > or = 40 years. Approximately 4.5 million hospital days and $865 billion in hospital charges were associated with primary ID hospitalizations over the study period. Lower respiratory tract infections were the most commonly listed ID (34.4%), followed by kidney, urinary tract, and bladder infections; cellulitis; and abdominal and rectal infections.

CONCLUSIONS

The ID hospitalization rate increased during 1998-2006, reflecting an increase in ID hospitalizations among adults aged > or = 30 years, particularly older adults. Differences in trends and patterns of ID hospitalizations were noted by sex, age group, and race. Lower respiratory tract infections accounted for the largest proportion of ID hospitalizations. Future efforts should focus on preventive measures and improving early interventions for IDs.

The Incidence of Molluscum contagiosum among American Indians and Alaska Natives

Background

The epidemiology of Molluscum contagiosum (MC) in the United States is largely unknown, despite the fact that the virus is directly communicable and large outbreaks occur. This study provides population-based estimates to describe the epidemiology of MC in the United States among American Indian and Alaska Native (AI/AN) persons. This population was selected because of the comprehensiveness and quality of available data describing utilization of out-patient services.

Principal Findings

Outpatient visits listing MC as a diagnosis in the Indian Health Service National Patient Information Reporting System during 2001–2005 were analyzed to assess patient characteristics, visit frequency and concurrent skin conditions. Outpatient visit rates and incidence rates were calculated based on known population denominators (retrospective cohort). Overall outpatient visit rates were also calculated for the general US population using national data. The average annual rate of MC-associated outpatient visits was 20.15/10,000 AI/AN persons for 2001–2005 (13,711 total visits), which was similar to the rate for the general US population (22.0/10,000 [95% CI: 16.9–27.1]). The incidence of MC-associated visits was 15.34/10,000. AI/AN children 1–4 years old had the highest incidence (77.12), more than twice that for children 5–14 years old (30.79); the incidence for infants (<1 year) was higher than that for adults. AI/AN persons living in the West region had the highest incidence, followed by those in the East and Alaska regions (26.96, 22.88 and 21.38, respectively). There were age-specific associations between MC and concurrent skin conditions (e.g., atopic dermatitis, eczema).

Conclusions

This study highlights the need for periodic population-based measurements to assess trends in incidence and healthcare utilization for MC in the United States. High rates of MC were found among AI/AN persons, especially among children <15 years old. The AI/AN population would benefit from greater availability of effective strategies for prevention and treatment of MCV infection.