Serum dioxin concentrations and risk of uterine leiomyoma in the Seveso Women's Health Study

Unusual Presentation of Leiomyoma in the Hindfoot

A leiomyoma is a benign smooth muscle tumor that is most commonly found in the uterus. Limited studies have reported leiomyoma of the foot, rendering it an usual finding. We present a case of a 57-year-old female patient who presented to the clinic for a painless mass on the posteromedial side of the right heel. It was diagnosed by the radiologist on MRI as a probable schwannoma. The patient underwent surgical excision of this mass which turned out to be a leiomyoma on pathology report. Although foot leiomyoma is a rare finding, leiomyoma should be listed in the differential diagnosis when evaluating foot soft tissue masses. It is difficult to confirm the diagnosis clinically and radiographically, yet a histologic evaluation can affirm the diagnosis. Surgical excision is the treatment of choice offering immediate symptomatic relief.

Transgenerational Transmission of 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) Effects in Human Granulosa Cells: The Role of MicroRNAs

Endocrine-disrupting chemicals (EDCs) might contribute to the increase in female-specific cancers in Western countries. 2,3,7,8-tetrachlordibenzo-p-dioxin (TCDD) is considered the "prototypical toxicant" to study EDCs' effects on reproductive health. Epigenetic regulation by small noncoding RNAs (sncRNAs), such as microRNAs (miRNA), is crucial for controlling cancer development. The aim of this study was to analyze transcriptional activity and sncRNA expression changes in the KGN cell line after acute (3 h) and chronic (72 h) exposure to 10 nM TCDD in order to determine whether sncRNAs' deregulation may contribute to transmitting TCDD effects to the subsequent cell generations (day 9 and day 14 after chronic exposure). Using Affymetrix GeneChip miRNA 4.0 arrays, 109 sncRNAs were found to be differentially expressed (fold change < -2 or >2; p-value < 0.05) between cells exposed or not (control) to TCDD for 3 h and 72 h and on day 9 and day 14 after chronic exposure. Ingenuity Pathway Analysis predicted that following the acute and chronic exposure of KGN cells, sncRNAs linked to cellular development, growth and proliferation were downregulated, and those linked to cancer promotion were upregulated on day 9 and day 14. These results indicated that TCDD-induced sncRNA dysregulation may have transgenerational cancer-promoting effects.

Alcohol consumption and the risk of new-onset uterine leiomyomas: a nationwide population-based study in 2.5 million Korean women aged 20 to 39 years

BACKGROUND

Uterine leiomyomas are the most common benign tumors in women of childbearing age. Although there are several studies reporting the positive association of drinking alcohol with the incidence of uterine leiomyomas, studies targeting Korean women are lacking.

OBJECTIVE

This study aimed to investigate the association between alcohol consumption and the risk of new-onset uterine leiomyomas in Korean women of early reproductive-age.

STUDY DESIGN

This was a retrospective nationwide population-based cohort study using the Korean National Health Insurance Service database. Participants comprised 2,512,384 asymptomatic Korean women aged 20 to 39 years who underwent a national health examination from 2009 to 2012. The follow-up period was from the date of the first national health examination to the date of diagnosis of new-onset uterine leiomyomas or December 2018 if no uterine leiomyomas were detected. The diagnosis of uterine leiomyomas required 2 outpatient records within a year or 1 inpatient record of International Classification of Diseases, Tenth Revision (ICD-10) codes of uterine leiomyomas (D25) in the Korean National Health Insurance Service. Exclusion criteria were previously diagnosed uterine leiomyomas during the screening period (January 2002 to the date of first health examination) or uterine leiomyoma diagnosis within 1 year of baseline examination. The associations of alcohol consumption, amount drunk per drinking session, and sustained drinking over time with the risk of new-onset uterine leiomyomas were investigated.

RESULTS

Approximately 6.1% of women aged 20 to 39 years were diagnosed with uterine leiomyomas after an average of 4.3 years. Alcohol consumption was associated with an increased incidence of new-onset uterine leiomyomas of 12% to 16% (hazard ratio, 1.12; 95% confidence interval, 1.11-1.14 for mild-to-moderate drinkers; hazard ratio, 1.16; 95% confidence interval, 1.12-1.20 for heavy drinkers). Drinking ≥1 days per week was associated with increased risk of uterine leiomyomas (hazard ratio, 1.11; 95% confidence interval, 1.10-1.12 for drinking 1 day per week; hazard ratio, 1.15; 95% confidence interval, 1.12-1.17 for drinking ≥3 days per week), and the association increased proportionately to the amount of alcohol consumed per drinking session (hazard ratio, 1.17; 95% confidence interval, 1.15-1.19 for ≥7 glasses per drinking session). Women who also reported alcohol consumption in the questionnaire administered 2 years later (sustained drinkers) exhibited a 20% increased risk of new-onset uterine leiomyomas (hazard ratio, 1.20; 95% confidence interval, 1.17-1.22) compared with women who answered that they did not drink alcohol at both times (sustained nondrinkers). In women who discontinued drinking, the risk was 3% (hazard ratio, 1.03; 95% confidence interval, 1.01-1.06), whereas in women who became drinkers, the risk was 14% (hazard ratio, 1.14; 95% confidence interval, 1.11-1.16).

CONCLUSION

Having an alcohol drinking habit, the amount of alcohol consumed per drinking session, and sustained drinking over 2 years were significantly associated with the risk of new-onset uterine leiomyomas. Avoiding or discontinuing drinking could lower the risk of new-onset uterine leiomyomas in early reproductive-age women.

The Environment, Leiomyomas, Latinas, and Adiposity Study: rationale and design

BACKGROUND

Uterine leiomyomas, commonly known as fibroids, are benign tumors in postmenarchal females. By the age of 35 years, approximately 30% of females will have fibroids, and by the age of 50 years, the prevalence approaches 70% with some studies reporting >85% prevalence in African American females. Previous studies evaluating the prevalence of fibroids have largely relied on self-reported fibroid diagnoses, which could have falsely underestimated prevalence because many females with fibroids are asymptomatic. Despite known differences in fibroid prevalence by race, there are very limited data on fibroid prevalence by ethnicity. The Latino population is the largest ethnic minority in the United States, yet there is no large study that utilizes ultrasound to confirm the presence of fibroids in Latina/Latinx females. In addition, fibroids have been associated with obesity and with diabetes mellitus, but the data have been inconsistent and at times conflicting.

OBJECTIVE

The Environment, Leiomyomas, Latinas, and Adiposity Study was designed to quantify the prevalence of uterine fibroids among Latina/Latinx females and understand the relationships between obesity, glucose dysregulation, and fibroid prevalence and growth. This article presents the study's design and reports early enrollment data.

STUDY DESIGN

The Environment, Leiomyomas, Latinas, and Adiposity Study is a 5-year longitudinal cohort study based in Southeast Michigan with the goal of recruiting 600 Latina/Latinx females between the ages of 21 and 50 years. Given the recruitment goals, developing a respectful, transparent, and trusting relationship between the study investigators and the community was a major priority. Thus, a community-engaged research approach was utilized in the design of the Environment, Leiomyomas, Latinas, and Adiposity Study. A community advisory board containing community leaders, largely from the Latinx community, provided input and direction during the entirety of the Environment, Leiomyomas, Latinas, and Adiposity Study design and rollout process. A minimum of 3 visits (orientation and consent, baseline, follow-up) will be conducted for each participant, with baseline and follow-up visits approximately 18 to 30 months apart. At each visit, interviewer and self-administered surveys will assess sociodemographic factors, health behaviors, health history, and social determinants of health. In addition, participants undergo a pelvic ultrasound examination and biologic samples are collected.

RESULTS

Using community-engaged approaches, we have successfully enrolled 633 Latina/Latinx females. The mean participant age is 37.5±7.04 years. The mean body mass index is 30.0±6.54 kg/m². First study visits have been initiated.

CONCLUSION

The objective of the Environment, Leiomyomas, Latinas, and Adiposity Study is to address the knowledge gap regarding uterine fibroids in the Latina/Latinx population. The Environment, Leiomyomas, Latinas, and Adiposity Study will generate ultrasound-confirmed evidence of the prevalence and growth patterns of uterine fibroids in this specific population while also examining the associations between obesity and laboratory-confirmed glucose dysregulation with uterine fibroid prevalence and growth patterns.

Experimental Evidence of 2,3,7,8-Tetrachlordibenzo-p-Dioxin (TCDD) Transgenerational Effects on Reproductive Health

Previous studies have demonstrated that endocrine disruptors (EDs) can promote the transgenerational inheritance of disease susceptibility. Among the many existing EDs, 2,3,7,8-tetrachlordibenzo-p-dioxin (TCDD) affects reproductive health, including in humans, following direct occupational exposure or environmental disasters, for instance the Agent Orange sprayed during the Vietnam War. Conversely, few studies have focused on TCDD multigenerational and transgenerational effects on human reproductive health, despite the high amount of evidence in animal models of such effects on male and female reproductive health that mimic human reproductive system disorders. Importantly, these studies show that paternal ancestral TCDD exposure substantially contributes to pregnancy outcome and fetal health, although pregnancy outcome is considered tightly related to the woman’s health. In this work, we conducted a systematic review of the literature and a knowledge synthesis in order (i) to describe the findings obtained in rodent models concerning TCDD transgenerational effects on reproductive health and (ii) to discuss the epigenetic molecular alterations that might be involved in this process. As ancestral toxicant exposure cannot be changed in humans, identifying the crucial reproductive functions that are negatively affected by such exposure may help clinicians to preserve male and female fertility and to avoid adverse pregnancy outcomes.

Impact of Contraception on Uterine Fibroids

Background and Objectives: Uterine fibroids develop in 25–40% of women of childbearing age; however, there are discrepancies resulting from population and socioeconomic differences. The pathogenesis of fibroids is not clear. The aim of the study was to assess the potential connection between the use of oral contraceptives and the occurrence of uterine fibroids in women of childbearing age. Materials and Methods: In this prospective, survey, case–control study, data were collected from Caucasian female patients (mean age = 30) using a questionnaire concerning the onset, duration and form of hormonal contraception, and medical and obstetrical history. The questionnaires were handed personally to hospitalized patients as well as distributed through Google forms on social media. Results: In a study group (n = 140) of patients using hormonal contraception, 37.8% of them were diagnosed with uterine fibroids, whereas among the patients not using hormonal contraception (n = 206), uterine fibroids were diagnosed in 59.6% of the patients. The most common hormonal contraception was two-component hormonal tablets used by 93.3% of the patients. Taking contraceptives was a uterine fibroids protective factor (OR = 0.4, p = 0.007). In the study group, 5.5% of the patients were pregnant and 60.42% were diagnosed with uterine fibroids (OR = 4.4, p < 0.000001). Conclusion: Contraception was found to be a protective factor for uterine fibroids among the women surveyed. The presented data confirm the theory about the hormonal dependence of uterine fibroids.

A Prospective Ultrasound Study of Plasma Polychlorinated Biphenyl Concentrations and Incidence of Uterine Leiomyomata

BACKGROUND

Uterine leiomyomata, or fibroids, are hormone-dependent neoplasms of the myometrium that can cause severe gynecologic morbidity. In previous studies, incidence of these lesions has been positively associated with exposure to polychlorinated biphenyls (PCBs), a class of persistent endocrine-disrupting chemicals. However, previous studies have been retrospective in design and none has used ultrasound to reduce disease misclassification.

METHODS

The Study of Environment, Lifestyle, and Fibroids is a prospective cohort of 1,693 reproductive-aged Black women residing in Detroit, Michigan (enrolled during 2010-2012). At baseline and every 20 months for 5 years, women completed questionnaires, provided blood samples, and underwent transvaginal ultrasound to detect incident fibroids. We analyzed 754 baseline plasma samples for concentrations of 24 PCB congeners using a case-cohort study design. We used multivariable Cox proportional hazards regression to estimate hazard ratios (HRs) and 95% confidence intervals for the association between plasma PCB concentrations and ultrasound-detected fibroid incidence over a 5-year period.

RESULTS

We observed little association between PCB congener concentrations and fibroid incidence. The HR for a one-standard deviation increase in log-transformed total PCBs was 0.94 (95% CI = 0.78, 1.1). The PCB congener with the largest effect estimate was PCB 187 (HR for a one-standard deviation increase in log-transformed exposure = 0.88, 95% CI = 0.73, 1.1). Associations did not seem to vary strongly across PCB groupings based on hormonal activity.

CONCLUSIONS

In this cohort of reproductive-aged Black women, plasma PCB concentrations typical of the contemporary general population were not appreciably associated with higher risk of fibroids.

Brominated flame retardants and organochlorine pesticides and incidence of uterine leiomyomata: A prospective ultrasound study

Uterine leiomyomata (UL) are hormone-responsive benign neoplasms. Brominated flame retardants and organochlorine pesticides (OCPs) can disrupt hormones involved in UL etiology.

METHODS

The Study of Environmental, Lifestyle, and Fibroids is a Detroit-area prospective cohort of 1693 Black women 23-35 years of age. At baseline and approximately every 20 months for 5 years, women completed questionnaires and underwent transvaginal ultrasounds. Using a case-cohort study design, we selected 729 UL-free participants at baseline and analyzed baseline plasma samples for polybrominated diphenyl ethers (PBDEs), a polybrominated biphenyl ether (PBB-153), and OCPs. We used Cox proportional hazard models to estimate hazard ratios (HRs) and 95% confidence intervals (CIs).

RESULTS

Compared with total PBDE plasma concentrations <50th percentile, adjusted HRs for the 50th-74th, 75th-89th, and ≥90th percentiles were 1.00 (95% CI = 0.68, 1.47), 1.04 (95% CI = 0.63, 1.68), and 0.85 (95% CI = 0.48, 1.50), respectively. HRs for PBB-153 plasma concentrations were generally similar to total PBDE plasma concentrations. Compared with total OCP plasma concentrations <50th percentile, HRs for the 50th-74th, 75th-89th, and ≥90th percentiles were 0.86 (95% CI = 0.57, 1.29), 0.73 (95% CI = 0.43, 1.22), and 0.58 (95% CI = 0.32, 1.04), respectively. HRs for individual PBDEs and OCPs were similar to their respective totals.

CONCLUSION

We found little support for an association between brominated flame retardant plasma concentrations and UL incidence, and some evidence of lower UL incidence with the highest OCP plasma concentrations.

Plastic wastes: environmental hazard and instrument for wealth creation in Nigeria

Combating the menace of plastic waste pollution has become a global environmental challenge. Plastic pollution is capable of affecting land, waterways and oceans as a large percentage of marine and land creatures have died due to the fact that plastic is non-biodegradable and it causes hazards to soil. It also emits toxic gasses when exposed or heated up. It blocks drainage lines and fill up land space causing floods and erosion thereby causing deterioration of the Nigerian roads. Plastics wastes are also harmful to human health; they may contain harmful acids which may lead to death. Nigeria, which is the biggest oil exporting country in Africa, relies mainly on the proceeds of the oil trade for its GDP and based strategy in growing her economy. However, with the declination of oil prices and increase in plastic wastes, the world is tending towards energy and sustainable development. Therefore, an urgent need for recycling plastic wastes into a solution for wealth creation is fundamental in Nigeria. This paper therefore seeks to identify favorable methods for recycling plastic wastes in Nigeria as a tool for solution to diversification and implementation. Evidence based examples are illustrated in the article with viable solution recommended for implementation.

Plastic Waste Environmental and Human Health Impacts

Plastics have become a vital asset for humanity. Plastics are known as synthetic materials produced from synthetic or semi-synthetic organic polymers derived from petro-based chemicals, able to displace traditional natural polymeric materials (wood, stone, ceramics, etc.). Plastics have malformed everyday life; usage is increasing, and annual production is likely to exceed 300 million tons by 2010. In this chapter, the authors blend current understanding of the benefits and concerns surrounding the use of plastics and look to future priorities, challenges, and opportunities. Plastics case serious environmental pollution such as soil pollution, water pollution, and air pollution. Application of proper rules and regulations for the production and use of plastics can reduce the toxic effects of plastics on human health and the environment.

The Seveso accident: A look at 40 years of health research and beyond

A 1976 chemical factory explosion near Seveso, Italy exposed residents to high levels of 2,3,7,8-tetracholorodibenzo-p-dioxin (TCDD or dioxin). Dioxin is a known human carcinogen and potent endocrine disruptor. It is highly lipophilic and has a long half-life in humans. Much of what we know and can learn about the risks of dioxin exposure on human health arose from the tragic circumstances of Seveso. This review aims to describe the Seveso accident, summarize the results of 40 years of research on the health of the Seveso population since the accident, and discuss next-stage research on the health of Seveso residents, their children, and grandchildren.

Risk for animal and human health related to the presence of dioxins and dioxin-like PCBs in feed and food

The European Commission asked EFSA for a scientific opinion on the risks for animal and human health related to the presence of dioxins (PCDD/Fs) and DL-PCBs in feed and food. The data from experimental animal and epidemiological studies were reviewed and it was decided to base the human risk assessment on effects observed in humans and to use animal data as supportive evidence. The critical effect was on semen quality, following pre- and postnatal exposure. The critical study showed a NOAEL of 7.0 pg WHO2005-TEQ/g fat in blood sampled at age 9 years based on PCDD/F-TEQs. No association was observed when including DL-PCB-TEQs. Using toxicokinetic modelling and taking into account the exposure from breastfeeding and a twofold higher intake during childhood, it was estimated that daily exposure in adolescents and adults should be below 0.25 pg TEQ/kg bw/day. The CONTAM Panel established a TWI of 2 pg TEQ/kg bw/week. With occurrence and consumption data from European countries, the mean and P95 intake of total TEQ by Adolescents, Adults, Elderly and Very Elderly varied between, respectively, 2.1 to 10.5, and 5.3 to 30.4 pg TEQ/kg bw/week, implying a considerable exceedance of the TWI. Toddlers and Other Children showed a higher exposure than older age groups, but this was accounted for when deriving the TWI. Exposure to PCDD/F-TEQ only was on average 2.4- and 2.7-fold lower for mean and P95 exposure than for total TEQ. PCDD/Fs and DL-PCBs are transferred to milk and eggs, and accumulate in fatty tissues and liver. Transfer rates and bioconcentration factors were identified for various species. The CONTAM Panel was not able to identify reference values in most farm and companion animals with the exception of NOAELs for mink, chicken and some fish species. The estimated exposure from feed for these species does not imply a risk.

Leiomyoma of the Foot: A Case Report

Leiomyomas are benign tumors of smooth muscle origin. They are most commonly found in the uterus, but cutaneous leiomyomas may be occasionally present in the extremities and cause pain secondary to mass effect. Few studies have reported leiomyoma of the foot, and leiomyoma of the heel is particularly rare. We present a case of a 41-year-old female who presented to our clinic for a tender nodule on the posterior aspect of her right heel. The tumor was surgically excised and biopsied revealing cutaneous leiomyoma.

Alcohol consumption and risk of uterine myoma: A systematic review and meta analysis

BACKGROUND

The published data about alcohol consumption and uterine myoma are scanty and controversial: some studies found positive association whereas other studies showed no association.

OBJECTIVES

To conduct a systematic review and meta-analysis to determine whether alcohol is a risk factor for myoma.

SEARCH STRATEGY

A MEDLINE/EMBASE search was carried out, supplemented by manual searches of bibliographies of the selected studies.

SELECTION CRITERIA

Articles published as full-length papers in English. In the review we included all identified studies. Otherwise, the inclusion criteria for studies included in the meta-analysis were: a) case-control or cohort studies, reporting original data; b) studies reporting original data on the association between alcohol consumption and myoma; c) diagnosis of myoma was ultrasound or histological confirmed and/or clinically based.

DATA COLLECTION AND ANALYSIS

A total of 6 studies were identified for the review and 5 studies were included in the meta-analysis. The primary outcome was the incidence of uterine myoma in ever versus never alcohol drinkers and when data were available, we also analyzed categories of alcohol intake. We assessed the outcomes in the overall population and then we performed a subgroup analysis according to study design. Pooled estimates of the odds ratios (OR) with 95% confidence interval (CI) were calculated using random effects models.

MAIN RESULTS

The summary OR (95%CI) of myoma forever versus never alcohol intake was 1.12 (0.94-1.34) with significant heterogeneity. The summary OR for current versus never drinking was 1.33 (1.01-1.76) with no heterogeneity.

CONCLUSIONS

Ever alcohol consumption is not associated with myoma risk. Based on the data of two studies, current alcohol drinkers had a slightly borderline increased risk of diagnosis of myoma. In consideration of the very limited number of studies and the suggestion of a potential increased risk among current drinkers, further studies are required.

A comparative assessment of major international disasters: the need for exposure assessment, systematic emergency preparedness, and lifetime health care

BACKGROUND

The disasters at Seveso, Three Mile Island, Bhopal, Chernobyl, the World Trade Center (WTC) and Fukushima had historic health and economic sequelae for large populations of workers, responders and community members.

METHODS

Comparative data from these events were collected to derive indications for future preparedness. Information from the primary sources and a literature review addressed: i) exposure assessment; ii) exposed populations; iii) health surveillance; iv) follow-up and research outputs; v) observed physical and mental health effects; vi) treatment and benefits; and vii) outreach activities.

RESULTS

Exposure assessment was conducted in Seveso, Chernobyl and Fukushima, although none benefited from a timely or systematic strategy, yielding immediate and sequential measurements after the disaster. Identification of exposed subjects was overall underestimated. Health surveillance, treatment and follow-up research were implemented in Seveso, Chernobyl, Fukushima, and at the WTC, mostly focusing on the workers and responders, and to a lesser extent on residents. Exposure-related physical and mental health consequences were identified, indicating the need for a long-term health care of the affected populations. Fukushima has generated the largest scientific output so far, followed by the WTCHP and Chernobyl. Benefits programs and active outreach figured prominently in only the WTC Health Program. The analysis of these programs yielded the following lessons: 1) Know who was there; 2) Have public health input to the disaster response; 3) Collect health and needs data rapidly; 4) Take care of the affected; 5) Emergency preparedness; 6) Data driven, needs assessment, advocacy.

CONCLUSIONS

Given the long-lasting health consequences of natural and man-made disasters, health surveillance and treatment programs are critical for management of health conditions, and emergency preparedness plans are needed to prevent or minimize the impact of future threats.

Epidemiology of Uterine Fibroids: From Menarche to Menopause

Uterine leiomyomata (UL) have a substantial impact on women's health, but relatively few studies have identified opportunities for primary prevention of these neoplasms. Most established risk factors are not modifiable, including premenopausal age, African ancestry, age at menarche, and childbearing history. The main challenge in studying UL is that a large proportion of tumors are asymptomatic. Herein, we review the epidemiology of UL from published studies to date. We highlight the advantages of ultrasound screening studies and the ways in which their innovative methods have helped clarify the etiology of disease. We conclude with a discussion of promising new hypotheses.

Endocrine-disrupting chemicals and uterine fibroids

Uterine fibroids are the most frequent gynecologic tumor, affecting 70% to 80% of women over their lifetime. Although these tumors are benign, they can cause significant morbidity and may require invasive treatments such as myomectomy and hysterectomy. Many risk factors for these tumors have been identified, including environmental exposures to endocrine-disrupting chemicals (EDCs) such as genistein and diethylstilbestrol. Uterine development may be a particularly sensitive window to environmental exposures, as some perinatal EDC exposures have been shown to increase tumorigenesis in both rodent models and human epidemiologic studies. The mechanisms by which EDC exposures may increase tumorigenesis are still being elucidated, but epigenetic reprogramming of the developing uterus is an emerging hypothesis. Given the remarkably high incidence of uterine fibroids and their significant impact on women's health, understanding more about how prenatal exposures to EDCs (and other environmental agents) may increase fibroid risk could be key to developing prevention and treatment strategies in the future.

Uterine fibroids

Uterine fibroids (also known as leiomyomas or myomas) are common clonal neoplasms of the uterus. Fibroids have both smooth muscle and fibroblast components, in addition to a substantial amount of fibrous extracellular matrix, which all contribute to the pathogenetic process. Fibroids are extremely heterogeneous in their pathophysiology, size, location and clinical symptomatology. They are also a part of a range of disease in which some variants have facets of malignant behaviour but overall are benign. Risk for fibroids is associated with race; black women have a higher risk of developing fibroids earlier in life than their white counterparts and also develop more-severe forms of the disease. Clinically, fibroids account for one-third to half of all hysterectomies and are associated with substantial morbidity and health care costs for women of reproductive age. Indeed, current treatments are primarily surgical and interventional; approximately three-quarters of all fibroid treatments are hysterectomies. However, clinical innovations are emerging in the use of progesterone receptor modulators as a medical therapy. New information is rapidly accumulating about the genetic subgroups that lead to fibroid formation, which might aid further understanding of the clinical heterogeneity of this disease and lead to individualized treatments. This information is a crucial development given the current lack of high-quality evidence on which to base therapeutic decisions.

Female Reproductive Disorders, Diseases, and Costs of Exposure to Endocrine Disrupting Chemicals in the European Union

CONTEXT

A growing body of evidence suggests that endocrine-disrupting chemicals (EDCs) contribute to female reproductive disorders.

OBJECTIVE

To calculate the associated combined health care and economic costs attributable to specific EDC exposures within the European Union (EU).

DESIGN

An expert panel evaluated evidence for probability of causation using the Intergovernmental Panel on Climate Change weight-of-evidence characterization. Exposure-response relationships and reference levels were evaluated, and biomarker data were organized from carefully identified studies from the peer-reviewed literature to represent European exposure and approximate burden of disease as it occurred in 2010. Cost-of-illness estimation used multiple peer-reviewed sources.

SETTING, PATIENTS AND PARTICIPANTS AND INTERVENTION

Cost estimation was carried out from a societal perspective, ie, including direct costs (eg, treatment costs) and indirect costs such as productivity loss.

RESULTS

The most robust EDC-related data for female reproductive disorders exist for 1) diphenyldichloroethene-attributable fibroids and 2) phthalate-attributable endometriosis in Europe. In both cases, the strength of epidemiological evidence was rated as low and the toxicological evidence as moderate, with an assigned probability of causation of 20%–39%. Across the EU, attributable cases were estimated to be 56 700 and 145 000 women, respectively, with total combined economic and health care costs potentially reaching €163 million and €1.25 billion.

CONCLUSIONS

EDCs (diphenyldichloroethene and phthalates) may contribute substantially to the most common reproductive disorders in women, endometriosis and fibroids, costing nearly €1.5 billion annually. These estimates represent only EDCs for which there were sufficient epidemiologic studies and those with the highest probability of causation. These public health costs should be considered as the EU contemplates regulatory action on EDCs.

A Prospective, Ultrasound-Based Study to Evaluate Risk Factors for Uterine Fibroid Incidence and Growth: Methods and Results of Recruitment

BACKGROUND

Uterine fibroids are common, benign, smooth-muscle tumors that can cause major morbidity for reproductive-age women, often requiring invasive treatment. Despite this personal and public health burden, no prior study has attempted to periodically screen fibroid-free women with ultrasound to detect incident disease and identify risk factors.

METHODS

We designed a study to prospectively investigate development of fibroids by enrolling women without a clinical diagnosis of fibroids and screening for fibroids with ultrasound at baseline. Enrollment procedures included extensive questionnaires and specimen collection (blood, urine, vaginal swabs). The cohort is followed at approximately 20-month intervals. At each follow-up there are updates to the questionnaire data, further specimen collection, and an ultrasound examination. We identify incident disease and measure tumor growth. The two exposures of primary interest are vitamin D insufficiency and reproductive tract infections. This manuscript provides a detailed description of the study methods, recruitment results, and participant characteristics.

RESULTS

The Study of Environment, Lifestyle and Fibroids enrolled 1,696 African American women aged 23-34 years. "Family and friends" was a leading recruitment source. More than 95% of participants contributed all the requested biological specimens at baseline. Study ultrasound examinations revealed undiagnosed fibroids in 378 women (22% of participants). The retention rate for the first follow-up was 87%.

CONCLUSIONS

Study design aspects likely to be important for long-term studies in young African Americans include personalized recruitment, multiple steps to the enrollment process that rely on the initiative of the participant, and methods for tracing highly mobile study subjects.

Prevalence, morbidity, and current medical management of uterine leiomyomas

BACKGROUND

Uterine leiomyoma is the most common pelvic tumor in women, but the actual prevalence is unknown.

OBJECTIVES

To review the literature on the prevalence of uterine leiomyoma, presenting symptoms, and medical management.

SEARCH STRATEGY

On April 1-30, 2014, a PubMed search for studies reported in English was conducted using the terms "uterine leiomyoma," "prevalence," and "symptoms." Another search was performed using the terms "uterine leiomyoma" and "treatment."

SELECTION CRITERIA

All trial types other than internet-only studies were included. Animal studies were excluded from the prevalence/symptom review, but included in the medical management review.

DATA COLLECTION AND ANALYSIS

Prevalence rates were recorded on the basis of imaging modality, cohort studied, ethnic origin, and age.

MAIN RESULTS

Studies involving asymptomatic women revealed a trend in prevalence similar to that in symptomatic women, and showed that leiomyomas are more common in this cohort than previously recognized. Affected patients can present with many complaints, but no single symptom has been shown to be specific for this tumor. Various medical therapies are reviewed, summarizing efficacy and toxicity.

CONCLUSIONS

Further research needs to be conducted on the prevalence in asymptomatic women. Current and future medical management options provide promising results in symptom reduction.

Persistent organic pollutants (POPs) and fibroids: results from the ENDO study

To evaluate the association between persistent organic pollutants (POPs) and uterine fibroids, we used previously collected data from a cohort of women aged 18-44 years undergoing laparoscopy or laparotomy at 14 participating hospital surgical centers (n=473). POP concentrations were measured in omental fat and serum. Presence of fibroids was defined on the basis of a postoperative diagnosis (n=99). Odds ratios (OR) and 95% confidence interval (CI) for each POP by biologic medium were estimated using unconditional logistic regression adjusted for identified covariates. Concentrations were higher in omental fat than in serum for all POPs. Serum p,p'-dichlorodiphenyldichloroethylene (p,p'-DDE) was the only POP associated with fibroids (per 1-SD increase in log-transformed p,p'-DDE OR (95% CI): 1.37 (1.05-1.80)). In analyses excluding women diagnosed with endometriosis, a number of polychlorinated biphenyls (PCBs) measured in omental fat were associated with fibroids (PCB 99: 1.64 (1.08, 2.49); PCB 138: 1.64 (1.03, 2.59); PCB 146: 1.54 (1.01, 2.37); PCB 153: 1.88 (1.12, 3.13); PCB 196: 1.60 (1.02, 2.51); PCB 206: 1.52 (1.01, 2.29)). Although exploratory, our study suggests that PCBs may be associated with fibroids in the absence of other gynecologic disorders such as endometriosis, but the associations varied by biologic media with more POPs emerging when quantified in fat.

Air pollution and risk of uterine leiomyomata

BACKGROUND

Air pollution, particularly from vehicle exhaust, has been shown to influence hormonal activity. However, it is unknown whether air pollution exposure is associated with the occurrence of uterine leiomyomata, a hormonally sensitive tumor of the uterus.

METHODS

For 85,251 women 25-42 years of age at enrollment in the Nurses' Health Study II, we examined proximity to major roadways and outdoor levels of particulate matter less than 10 microns (PM10) or 2.5 microns (PM2.5) or between 10 and 2.5 microns (PM10-2.5) in diameter for all residential addresses from September 1989 to May 2007. To be eligible for this analysis, a woman had to be alive and respond to questionnaires, premenopausal with an intact uterus, and without diagnoses of cancer or prevalent uterine leiomyomata. Incidence of ultrasound- or hysterectomy-confirmed uterine leiomyomata and covariates were reported on biennial questionnaires sent through May 2007. Multivariable time-varying Cox proportional hazard models were used to estimate the relationship between distance to road or PM exposures and uterine leiomyomata risk.

RESULTS

During 837,573 person-years of follow-up, there were 7760 incident cases of uterine leiomyomata. Living close to a major road and exposures to PM10 or PM10-2.5 were not associated with an increased risk of uterine leiomyomata. However, each 10 μg/m increase in 2-year average, 4-year average, or cumulative average PM2.5 was associated with an adjusted hazard ratio of 1.08 (95% confidence interval = 1.00-1.17), 1.09 (0.99-1.19), and 1.11 (1.03-1.19), respectively.

CONCLUSIONS

Chronic exposure to PM2.5 may be associated with a modest increased risk of uterine leiomyomata.

Risk for estrogen-dependent diseases in relation to phthalate exposure and polymorphisms of CYP17A1 and estrogen receptor genes

Evidence has shown that polymorphisms of various genes known to be involved in estrogen biosynthesis and function are associated with estrogen-dependent diseases (EDDs). These genes include CYP17A1, estrogen receptor 1 (ESR1), and 2 (ESR2). Phthalates are considered estrogenic endocrine disruptors, and recent research has suggested that they may act as a risk factor for EDDs. However, extremely few studies have assessed the effects of gene-environment interaction on these diseases. We recruited 44 patients with endometriosis or adenomyosis, 36 patients with leiomyoma, and 69 healthy controls from a medical center in Taiwan between 2005 and 2007. Urine samples were collected and analyzed for seven phthalate metabolites using liquid chromatography tandem mass spectrometry. Peripheral lymphocytes were used for DNA extraction to determine the genotype of CYP17A1, ESR1, and ESR2. Compared to controls, patients with leiomyoma had significantly higher levels of total urinary mono-ethylhexyl phthalate (ΣMEHP) (52.1 vs. 29.6 μg/g creatinine, p = 0.040), mono-n-butyl phthalate (MnBP) (75.4 vs. 51.3 μg/g creatinine, p = 0.019), and monoethyl phthalate (MEP) (103.7 vs. 59.3 μg/g creatinine, p = 0.031). In contrast, patients with endometriosis or adenomyosis showed a marginally increased level of urinary MEHP only. Subjects who were homozygous for both the ESR1 C allele (rs2234693) and CYP17A1 C allele (rs743572) showed a significantly increased risk for leiomyoma (OR = 19.8; 95 % CI, 1.70; 231.5; p = 0.017) relative to subjects with other genotypes of ESR1 and CYP17A1. These results were obtained after adjusting for age, cigarette smoking, MEHP level, GSTM1 genotype and other covariates. Our results suggested that both CYP17A1 and ESR1 polymorphisms may modulate the effects of phthalate exposure on the development of leiomyoma.

Cancer and non-cancer excess mortality resulting from mixed exposure to polychlorinated biphenyls and polychlorinated dibenzofurans from contaminated rice oil: "Yusho"

PURPOSE

In 1968, rice oil contaminated with polychlorinated biphenyls and polychlorinated dibenzofurans caused a severe outbreak of food poisoning in Japan and was termed locally as "Yusho" (oil disease). In our previous study, we found that area-based standardized mortality ratios (SMRs) of some diseases were elevated shortly after the incident. This previous study, however, was unable to determine whether these elevated SMRs were a result of other area-specific factors. To overcome this limitation, we obtained mortality data from the 5 years before the incident and conducted an area-based study using vital statistics records dating from 1963 to 2002.

METHODS

The population of Nagasaki Prefecture was set as the reference population for calculating SMRs. We also included data on cause-specific mortality attributable to cancer and expanded the population to encompass two severely exposed areas where contaminated rice oil was distributed (namely Tamanoura and Naru). We also calculated SMRs in the remainder of the Shimo-Goto region, excluding the exposed area, which was used as a comparison area.

RESULTS

Even after considering the time trends in mortality before the incident, mortality due to diabetes mellitus and heart disease, as well as all-cause mortality, was found to be elevated shortly afterward. Additionally, mortalities due to uterine cancer in Tamanoura and leukemia were also elevated at 30-34 and 10-59 years after the event in both exposed areas, respectively. SMRs for leukemia in Tamanoura were as high as 3.0 (95% confidence interval 1.4-6.2) and 2.4 (1.2-4.8) 10-19 years later. In this period, SMRs for leukemia in the comparison area were not elevated.

CONCLUSIONS

Further epidemiological studies are needed regarding this rice-oil, "Yusho" outbreak, especially with regard to cancer and non-cancer mortality.

Laparoscopic radiofrequency fibroid ablation: phase II and phase III results

BACKGROUND AND OBJECTIVES

To review phase II and phase III treatments of symptomatic uterine fibroids (myomas) using laparoscopic radiofrequency volumetric thermal ablation (RFVTA).

METHODS

We performed a retrospective, multicenter clinical analysis of 206 consecutive cases of ultrasound-guided laparoscopic RFVTA of symptomatic myomas conducted on an outpatient basis under two phase II studies at 2 sites (n = 69) and one phase III study at 11 sites (n = 137). Descriptive and exploratory, general trend, and matched-pair analyses were applied.

RESULTS

From baseline to 12 months in the phase II study, the mean transformed symptom severity scores improved from 53.9 to 8.8 (P < .001) (n = 57), health-related quality-of-life scores improved from 48.5 to 92.0 (P < .001) (n = 57), and mean uterine volume decreased from 204.4 cm(3) to 151.4 cm(3) (P = .008) (n = 58). Patients missed a median of 4 days of work (range, 2-10 days). The rate of possible device-related adverse events was 1.4% (1 of 69). In the phase III study, approximately 98% of patients were assessed at 12 months, and their transformed symptom severity scores, health-related quality-of-life scores, mean decrease in uterine volume, and mean menstrual bleeding reduction were also significant. Patients in phase III missed a median of 5 days of work (range, 1-29 days). The rate of periprocedural device-related adverse events was 3.5% (5 of 137). Despite the enrollment requirement for patients in both phases to have completed childbearing, 4 pregnancies occurred within the first year after treatment.

CONCLUSIONS

RFVTA does not require any uterine incisions and provides a uterine-sparing procedure with rapid recovery, significant reduction in uterine size, significant reduction or elimination of myoma symptoms, and significant improvement in quality of life.

Proceedings from the Third National Institutes of Health International Congress on Advances in Uterine Leiomyoma Research: comprehensive review, conference summary and future recommendations

BACKGROUND Uterine fibroids are the most common gynecologic tumors in women of reproductive age yet the etiology and pathogenesis of these lesions remain poorly understood. Age, African ancestry, nulliparity and obesity have been identified as predisposing factors for uterine fibroids. Symptomatic tumors can cause excessive uterine bleeding, bladder dysfunction and pelvic pain, as well as associated reproductive disorders such as infertility, miscarriage and other adverse pregnancy outcomes. Currently, there are limited noninvasive therapies for fibroids and no early intervention or prevention strategies are readily available. This review summarizes the advances in basic, applied and translational uterine fibroid research, in addition to current and proposed approaches to clinical management as presented at the 'Advances in Uterine Leiomyoma Research: 3rd NIH International Congress'. Congress recommendations and a review of the fibroid literature are also reported. METHODS This review is a report of meeting proceedings, the resulting recommendations and a literature review of the subject. RESULTS The research data presented highlights the complexity of uterine fibroids and the convergence of ethnicity, race, genetics, epigenetics and environmental factors, including lifestyle and possible socioeconomic parameters on disease manifestation. The data presented suggest it is likely that the majority of women with uterine fibroids will have normal pregnancy outcomes; however, additional research is warranted. As an alternative to surgery, an effective long-term medical treatment for uterine fibroids should reduce heavy uterine bleeding and fibroid/uterine volume without excessive side effects. This goal has not been achieved and current treatments reduce symptoms only temporarily; however, a multi-disciplined approach to understanding the molecular origins and pathogenesis of uterine fibroids, as presented in this report, makes our quest for identifying novel targets for noninvasive, possibly nonsystemic and effective long-term treatment very promising. CONCLUSIONS The Congress facilitated the exchange of scientific information among members of the uterine leiomyoma research and health-care communities. While advances in research have deepened our knowledge of the pathobiology of fibroids, their etiology still remains incompletely understood. Further needs exist for determination of risk factors and initiation of preventive measures for fibroids, in addition to continued development of new medical and minimally invasive options for treatment.

Potential mechanisms of aberrant DNA hypomethylation on the x chromosome in uterine leiomyomas

We recently found that aberrant DNA hypomethylation is more common on the X chromosome than on other chromosomes in uterine leiomyomas by genome-wide DNA methylation profiling. To investigate the mechanism of aberrant hypomethylation on the X chromosome in uterine leiomyomas, we analyzed methylome and transcriptome data from three cases of leiomyomas and the adjacent myometrium. We found that eleven of the aberrantly hypomethylated genes on the X chromosome were common to the three cases. None of these 11 genes were transcriptionally upregulated in the leiomyoma. However, one of them, TSPYL2, was hypomethylated in 68% of multiple leiomyoma specimens. The incidence of aberrant hypomethylation of TSPYL2 was comparable to that of the MED12 mutation (68%), which is known to be detected at a high frequency in uterine leiomyomas. We also analyzed the aberration of the X chromosome inactivation (XCI) mechanism in uterine leiomyomas. Hypomethylation was not enriched in the imprinted genes, suggesting that dysfunction of polycomb repressive complexes is not involved in the aberrant hypomethylation on the X chromosome. The expression analysis of XCI-related genes revealed that the XIST and SATB1 expression was downregulated in 36% and 46% of 11 leiomyoma specimens, respectively, while the HNRNPU and SMCHD1 expression was not altered. In conclusion, the aberration of XCI-related genes such as SATB1 or XIST may be involved in aberrant hypomethylation on the X chromosome in a certain population of the patients with uterine leiomyomas. TSPYL2 of the aberrantly hypomethylated genes on the X chromosome can be used as a biomarker of uterine leiomyomas.

Tracking hazardous air pollutants from a refinery fire by applying on-line and off-line air monitoring and back trajectory modeling

The air monitors used by most regulatory authorities are designed to track the daily emissions of conventional pollutants and are not well suited for measuring hazardous air pollutants that are released from accidents such as refinery fires. By applying a wide variety of air-monitoring systems, including on-line Fourier transform infrared spectroscopy, gas chromatography with a flame ionization detector, and off-line gas chromatography-mass spectrometry for measuring hazardous air pollutants during and after a fire at a petrochemical complex in central Taiwan on May 12, 2011, we were able to detect significantly higher levels of combustion-related gaseous and particulate pollutants, refinery-related hydrocarbons, and chlorinated hydrocarbons, such as 1,2-dichloroethane, vinyl chloride monomer, and dichloromethane, inside the complex and 10 km downwind from the fire than those measured during the normal operation periods. Both back trajectories and dispersion models further confirmed that high levels of hazardous air pollutants in the neighboring communities were carried by air mass flown from the 22 plants that were shut down by the fire. This study demonstrates that hazardous air pollutants from industrial accidents can successfully be identified and traced back to their emission sources by applying a timely and comprehensive air-monitoring campaign and back trajectory air flow models.

Role of endocrine disrupting chemicals in the occurrence of benign uterine leiomyomata: special emphasis on AhR tissue levels

Although benign uterine leiomyomata (LMA) is the most common reproductive tumor in premenopausal women, its etiology is largely unknown. We aimed in the present study to demonstrate the potential role of environmental factors with estrogenic activity in tumor etiology by focusing on the role of aryl hydrocarbon receptor (AhR) which mediates the effects of many environmental endocrine disruptors and contributes to the loss of normal ovarian function in polluted environments. This case-control study aimed to compare the interactions between AhR and lifestyle factors in a clinical setting for the first time among 138 newly diagnosed LMA patients and 138 normal controls who lived in Tehran and Mashhad, respectively, during the last 10 years. To conduct immunohistochemical studies using appropriate monoclonal antibodies, 30 cases were selected retrospectively from 2009-2011 from the pathology departments of two university hospitals in Tehran. Although the levels of sex steroid receptors were similar in adjacent myometrium and uterine leiomyomas of all cases, AhR was significantly overexpressed (p=0.034, OR=1.667) in uterine LMA and this overexpression was correlated with living in Tehran [(p=0.04, OR=16 (1.216-210.58)], smoking[P=0.04, OR=2.085 (1.29-3.371)], living near polycyclic aromative hydrocarbon producing companies [p=0.007, OR=2.22 (1.256-3.926)] and eating grilled meat [p=0.042, OR=1.28 (1.92-3.842)]. Our study contributes to the understanding of the effects of EDCs on AhR levels as well as women's health and points out possible risk factors for the development and growth of uterine LMA. It seems that the development of LMA could be the result of interactions between hormonal and environmental factors.

Hair relaxer use and risk of uterine leiomyomata in African-American women

Hair relaxers are used by millions of black women, possibly exposing them to various chemicals through scalp lesions and burns. In the Black Women's Health Study, the authors assessed hair relaxer use in relation to uterine leiomyomata incidence. In 1997, participants reported on hair relaxer use (age at first use, frequency, duration, number of burns, and type of formulation). From 1997 to 2009, 23,580 premenopausal women were followed for incident uterine leiomyomata. Multivariable Cox regression was used to estimate incidence rate ratios and 95% confidence intervals. During 199,991 person-years, 7,146 cases of uterine leiomyomata were reported as confirmed by ultrasound (n = 4,630) or surgery (n = 2,516). The incidence rate ratio comparing ever with never use of relaxers was 1.17 (95% confidence interval (CI): 1.06, 1.30). Positive trends were observed for frequency of use (P(trend) < 0.001), duration of use (P(trend) = 0.015), and number of burns (P(trend) < 0.001). Among long-term users (≥10 years), the incidence rate ratios for frequency of use categories 3-4, 5-6, and ≥7 versus 1-2 times/year were 1.04 (95% CI: 0.92, 1.19), 1.12 (95% CI: 0.99, 1.27), and 1.15 (95% CI: 1.01, 1.31), respectively (P(trend) = 0.002). Risk was unrelated to age at first use or type of formulation. These findings raise the hypothesis that hair relaxer use increases uterine leiomyomata risk.

Uterine leiomyomata in a cohort of Great Lakes sport fish consumers

Diet and endocrine disrupting persistent organic pollutants (POPs) have been associated with gynecologic conditions including uterine leiomyomata (UL), endometriosis, and ovarian cysts. Great Lakes sport fish consumption is a source of exposure to POPs such as p,p'-diphenyldichloroethene (DDE) and polychlorinated biphenyls (PCBs). This study was designed to examine retrospectively the effects Great Lakes sport fish consumption on the incidence of UL and to examine the effects of DDE and PCB serum levels on prevalent UL in women participating in the Great Lakes Fish Consumption Study. We hypothesized that associations of exposures with UL would be modified by breastfeeding status. Years of sport fish consumption, demographic, health, and reproductive data were assessed by survey. In a subgroup, serum was collected and tested for DDE and PCB levels. Effects of years of Great Lakes sport fish and sport fish consumption were modeled using time-dependent Cox proportional hazards regression and effects of POP exposures on UL were modeled using multiple logistic regression. Years of sport fish consumption were associated with UL, with an incidence rate ratio of 1.2 (95% CI 1.0-1.3) for each 10-year increment of fish consumption. Summary measures of POP exposures in the overall group were not associated with UL. In the subgroup of women who never breastfed and in whom PCB measurements were available, however, UL was significantly associated with PCBs and groupings of estrogenic, antiestrogenic, and dioxin-like PCBs. These findings support the possibility that PCB exposures from fish consumption may increase the risk of UL and highlight the importance of additional studies exploring biologic pathways by which they could be acting.

Plastics and health risks

By 2010, the worldwide annual production of plastics will surpass 300 million tons. Plastics are indispensable materials in modern society, and many products manufactured from plastics are a boon to public health (e.g., disposable syringes, intravenous bags). However, plastics also pose health risks. Of principal concern are endocrine-disrupting properties, as triggered for example by bisphenol A and di-(2-ethylhexyl) phthalate (DEHP). Opinions on the safety of plastics vary widely, and despite more than five decades of research, scientific consensus on product safety is still elusive. This literature review summarizes information from more than 120 peer-reviewed publications on health effects of plastics and plasticizers in lab animals and humans. It examines problematic exposures of susceptible populations and also briefly summarizes adverse environmental impacts from plastic pollution. Ongoing efforts to steer human society toward resource conservation and sustainable consumption are discussed, including the concept of the 5 Rs--i.e., reduce, reuse, recycle, rethink, restrain--for minimizing pre- and postnatal exposures to potentially harmful components of plastics.

New directions in the epidemiology of uterine fibroids

Although uterine leiomyomata (fibroids) have been the leading indication for hysterectomy in the United States for decades, the epidemiological data on fibroid prevalence and risk factors are limited. Given the hormonal dependence of fibroids, most earlier studies focused on reproductive or hormonal factors. Recent analyses have extended that focus to other areas. We present previously unpublished data on the association between reproductive tract infections and fibroids that highlight the need for more detailed studies. Our review suggests that metabolic, dietary, stress, and environmental factors may also play a role in fibroid development.

Proceedings from the conference on Reproductive Problems in Women of Color

The purpose of the National Institutes of Health conference on Reproductive Problems in Women of Color that convened on July 25, 2009 was to bring investigators together to examine data related to reproductive health care access and ethnic disparities in reproductive problems, fertility treatments, and pregnancy outcomes. One of the goals discussed at this conference was to initiate a research network of investigators interested in studying these problems through the development of an American Society of Reproductive Medicine special interest group and Society of Assisted Reproductive Technology writing groups.

Mortality after exposure to polychlorinated biphenyls and polychlorinated dibenzofurans: a 40-year follow-up study of Yusho patients

A 40-year follow-up study was conducted to examine mortality among 1,664 patients in Japan suffering from "Yusho," a disease caused by ingestion of rice oil contaminated with polychlorinated biphenyls and polychlorinated dibenzofurans. To evaluate the effects of exposure on mortality, the authors calculated standardized mortality ratios. National mortality rates for major causes of death were used as reference points. A total of 1,596 Yusho patients (95.9%) were followed until death or the end of the study (December 31, 2007). The standardized mortality ratios for most major causes of death were not significantly elevated, with the exceptions of all types of cancer (standardized mortality ratio (SMR) = 1.37, 95% confidence interval (CI): 1.11, 1.66), liver cancer (SMR = 1.82, 95% CI: 1.06, 2.91), and lung cancer (SMR = 1.75, 95% CI: 1.14, 2.57) in males. In addition, the standardized mortality ratios for all cancers, liver cancer, and lung cancer among males tended to decrease over time. Results from this study suggest that the carcinogenicity of polychlorinated biphenyls and polychlorinated dibenzofurans must be taken into account when evaluating mortality risk.

Regression analysis of a disease onset distribution using diagnosis data

We consider methods for estimating the effect of a covariate on a disease onset distribution when the observed data structure consists of right-censored data on diagnosis times and current status data on onset times amongst individuals who have not yet been diagnosed. Dunson and Baird (2001, Biometrics 57, 306-403) approached this problem using maximum likelihood, under the assumption that the ratio of the diagnosis and onset distributions is monotonic nondecreasing. As an alternative, we propose a two-step estimator, an extension of the approach of van der Laan, Jewell, and Petersen (1997, Biometrika 84, 539-554) in the single sample setting, which is computationally much simpler and requires no assumptions on this ratio. A simulation study is performed comparing estimates obtained from these two approaches, as well as that from a standard current status analysis that ignores diagnosis data. Results indicate that the Dunson and Baird estimator outperforms the two-step estimator when the monotonicity assumption holds, but the reverse is true when the assumption fails. The simple current status estimator loses only a small amount of precision in comparison to the two-step procedure but requires monitoring time information for all individuals. In the data that motivated this work, a study of uterine fibroids and chemical exposure to dioxin, the monotonicity assumption is seen to fail. Here, the two-step and current status estimators both show no significant association between the level of dioxin exposure and the hazard for onset of uterine fibroids; the two-step estimator of the relative hazard associated with increasing levels of exposure has the least estimated variance amongst the three estimators considered.