Increased female autosomal burden of rare copy number variants in human populations and in autism families.

Autosomal genetic variation is presumed equivalent in males and females and makes a major contribution to disease risk. We set out to identify whether maternal copy number variants (CNVs) contribute to autism spectrum disorders (ASDs). Surprisingly, we observed a higher autosomal burden of large, rare CNVs in females in the population, reflected in, but not unique to, ASD families. Meta-analysis across control data sets confirms female excess in CNV number (P=2.1 × 10(-5)) and gene content (P=4.1 × 10(-3)). We additionally observed CNV enrichment in ASD mothers compared with control mothers (P=0.03). We speculate that tolerance for CNV burden contributes to decreased female fetal loss in the population and that ASD-specific maternal CNV burden may contribute to high sibling recurrence. These data emphasize the need for study of familial CNV risk factors in ASDs and the requirement of sex-matched comparisons.

Phthalate exposure and pubertal development in a longitudinal study of US girls.

STUDY QUESTION: Does phthalate exposure during early childhood alter the timing of pubertal development in girls? SUMMARY ANSWER: Urinary concentrations of high-molecular weight phthalate (high-MWP) metabolites are associated with later pubarche. WHAT IS KNOWN ALREADY: Phthalates are anti-androgenic environmental agents known to alter early development, with possible effects on pubertal onset. STUDY DESIGN, SIZE, AND DURATION: This multi-ethnic study included 1239 girls from New York City, greater Cincinnati, and the San Francisco Bay Area who were 6-8 years old at enrollment (2004-2007) and who were followed until 2011. PARTICIPANTS/MATERIALS, SETTING, METHODS Phthalate metabolites were measured in urine collected at enrollment from 1170 girls; concentrations ranged from <1 to >10,000 µg/l. Breast and pubic hair stages and body size were assessed one to two times annually to determine the age at transition from stage 1 to 2 for breast and pubic hair development. Associations between exposures and pubertal ages were estimated using Cox proportional hazard ratios (HR) with 95% confidence intervals (CI) and survival analyses. Associations were examined with respect to age-specific body mass-index percentile, one of the strongest predictors of pubertal onset. MAIN RESULTS AND THE ROLE OF CHANCE: Urinary concentrations of high-MWP including di(2-ethylhexyl) phthalate (ΣDEHP) metabolites were associated with later pubic hair development during 7 years of observation. The relationship was linear and was stronger among normal-weight girls. Among normal-weight girls, age at pubic hair stage 2 (PH2) was 9.5 months older for girls in the fifth compared with the first quintile of urinary ΣDEHP (medians: 510 and 59 µg/g creatinine, respectively; adjusted HR 0.70, CI 0.53-0.93, P-trend 0.005. Age at first breast development was older for fifth quintile of mono-benzyl phthalate versus first (HR 0.83, CI 0.68-1.02; P-trend 0.018). No associations were observed between low-molecular weight phthalate urinary metabolite concentrations and age at pubertal transition in adjusted analyses. LIMITATIONS, REASONS FOR CAUTION: While there is evidence that phthalate exposures are fairly consistent over time, the exposure measure in this study may not reflect an earlier, more susceptible window of exposure. We investigated alternative explanations that might arise from exposure misclassification or confounding. WIDER IMPLICATIONS OF THE FINDINGS: Phthalates are widespread, hormonally active pollutants that may alter pubertal timing. Whether exposures delay or accelerate pubertal development may depend on age at exposure as well as other factors such as obesity and exposures earlier in life. Whether exposures act independently or as part of real life mixtures may also change their effects on maturation from birth through childhood. STUDY FUNDING/COMPETING INTEREST(S): This project was supported by the US National Institutes of Health, Environmental Protection Agency, New York State Empire Clinical Research Investigator Program and the Avon Foundation. L.H.K. is employed by Kaiser Permanente. The remaining authors declare they have no actual or potential competing financial interests.

Perfluorooctanoate and changes in anthropometric parameters with age in young girls in the Greater Cincinnati and San Francisco Bay Area.

METHODS: We conducted a study of per- and polyfluoroalkyl substance biomarkers, including PFOA, in girls from Greater Cincinnati (CIN, N = 353) and the San Francisco Bay Area (SFBA, N = 351). PFOA was measured in the baseline serum sample collected in 2004-2007 of 704 girls at age 6-8 years. Mixed effects models were used to derive the effect of PFOA on BMI, waist-to-height and waist-to-hip ratios over increasing age in this longitudinal cohort. RESULTS: Median PFOA serum concentrations were 7.3 (CIN) and 5.8 (SFBA) ng/mL, above the U.S. population median for children 12-19 years in 2005-2006 (3.8 ng/mL). Log-transformed serum PFOA had a strong inverse association with BMIz in the CIN girls (p = 0.0002) and the combined two-site data (p = 0.0008); the joint inverse effect of PFOA and Age*PFOA weakened at age at 10-11 years. However, in the SFBA group alone, the relationship was not significant (p = 0.1641) with no evidence of changing effect with age. The effect of PFOA on waist:height ratio was similar to BMIz at both sites, but we did not find a significant effect of PFOA on waist:hip ratio in either the CIN or SFBA girls. CONCLUSIONS: PFOA is associated with decreased BMI and waist:height ratio in young girls, but the strength of the relationship decreases with age. Site heterogeneity may be due to greater early life exposure in Cincinnati. DISCLAIMER: The findings and conclusions in this report are those of the authors and do not necessarily represent the official position of the Centers for Disease Control and Prevention. Use of trade names is for identification only and does not imply endorsement by the CDC, the Public Health Service, or the US Department of Health and Human Services.

Bone mass and subtle abnormalities in ovulatory function in healthy women.

Women with occasional anovulatory or short luteal phase menstrual cycles have been reported to lose bone mineral density (BMD) at a greatly accelerated rate compared to women without such abnormalities. To investigate this association, we performed a longitudinal study of BMD in a group of healthy premenopausal women enrolled in a comprehensive study of ovulatory function. Subjects had collected daily urine samples that were analyzed for estrone and progesterone metabolites by enzyme-linked immunoassay. The 53 participants collected urine for an average of 4.1 cycles. Computer algorithms identified 7 (13.2%) women with luteal phase abnormalities (> 1 anovulatory cycle or cycle with luteal phase length < or = 10 days) and 17 (32.1%) women with other menstrual abnormalities. Areal BMD (grams per cm2) was measured at the lumbar spine, hip, and whole body using dual energy x-ray absorptiometry; BMD was measured 2-3 times over an average observation period of 17.5 months. At baseline, women with luteal abnormalities had mean BMD similar to those of the 29 women with no abnormal cycles: lumbar spine, 1.06 vs. 1.09 g/cm2; total hip, 0.95 vs. 0.94 g/cm2; whole body, 1.15 vs. 1.11 g/cm2 (P > 0.10; adjusted for age and weight at baseline, parity, physical activity level, and calcium intake). When compared at follow-up to women with no abnormal cycles, women with luteal abnormalities tended to gain BMD at the spine and hip (P > 0.10). On whole body measurement, women with luteal abnormalities tended to lose BMD compared to women with no abnormal cycles (-1.1%/yr vs. 0%/yr; P = 0.08); however, the magnitude of loss was not unusual for women in this age range and was within the coefficient of variation for replicate measurements. Neither mean luteal phase length, percent time in luteal phase, nor average daily excretion of progesterone metabolites was associated with baseline BMD or percent annual change in BMD at any measurement site. Thus, we did not confirm a relationship between luteal abnormalities and accelerated bone loss in this population of healthy premenopausal women.

Current trends in the incidence of neural tube defects.

To verify and investigate the reported decline of neural tube defects (NTDs) in the last decade, data from three different sources were examined: the Birth Defects Monitoring Program (BDMP), composed of newborn discharge diagnoses; the population-base Metropolitan Atlanta Congenital Defects Program (MACDP); and the National Center for Health Statistics (NCHS), whose data include only live births. Although the three systems use different methods of ascertaining cases, all data bases showed a decreasing trend in NTD rates, with annual percent decreases of 3.1% for NCHS, 5.7% for BDMP, and 7.7% for MACDP. The decrease was noted in all variables examined: race, sex, and birth status for each defect. NTD rates appear to be declining more rapidly in females than in males. Further, the rate among stillborn infants decreased more than the rate among live-born infants. The exclusion of stillbirths in the NCHS data may contribute to its low rate of decline for female anencephalics. Data from England showed a larger average annual decrease (10.6%) than did data from the United States. Although reasons for the overall decline are not verifiable, a variety of explanations are suggested for this decline and for the difference in NTD rate decline noted between live births and stillbirths. The overall decline in NTD rates should be investigated with respect to etiology; recognition of the decline is useful for planning and evaluating health care programs.

Cigarette smoking and effects on menstrual function.

OBJECTIVE: To examine the relationship between smoking and menstrual function, using biologic measures rather than self-report of menstrual cycle characteristics. METHODS: In a prospective study, 408 women collected urine daily for one to seven menstrual segments (cycles), maintained daily diaries, and completed detailed interviews. Smoking data from the diaries were averaged over each segment and verified by cotinine assay. Urine samples were analyzed for metabolites of steroid hormones to define the day of ovulation and various menstrual characteristics, including: 1) segment, follicular, luteal phase, and menses length, 2) variability, and 3) anovulation. RESULTS: Heavy smoking (at least 20 cigarettes per day) was associated with nearly four times the risk of short segment (less than 25 days) as was nonsmoking (adjusted odds ratio 3.8, 95% confidence limits 1.1, 12.7). Mean segment length was on average 2.6 days shorter with heavy versus no smoking (95% confidence limits 0.14, 5.0), due almost entirely to shortening of the follicular phase. Women who smoked an average of ten or more cigarettes per day had significantly more variable segment and menses lengths than nonsmokers. Based on small numbers, the data suggested that with greater smoking, there was a possible increased risk of anovulation and short luteal phase. Segments of exsmokers with ten or more pack-years of exposure were more likely to be short and have shorter luteal phases than those of never smokers. CONCLUSION: The effects found in this study of smoking on the menstrual cycle might explain in part associations of smoking with other reproductive endpoints, such as subfecundity and early menopause.

Influence of exposure assessment methods on risk estimates in an epidemiologic study of total trihalomethane exposure and spontaneous abortion.

Trihalomethanes are common contaminants of chlorinated drinking water. Studies of their health effects have been hampered by exposure misclassification, due in part to limitations inherent in using utility sampling records. We used two exposure assessment methods, one based on utility-wide sampling averages, and one based on measurements from the utility sampling site closest to the subject's residence, to reestimate total trihalomethane (TTHM) exposure for 4212 participants in a preexisting study of risk factors for spontaneous abortion (SAB). For both approaches we performed unweighted, weighted, and subset analyses. The weighted and subset analyses were intended to reduce exposure misclassification, and were based on within-utility variance in TTHM measurements for the utility-wide average approach, and the distance between the subject's residence and sampling site for the closest-site approach. In general, the utility-wide average methods produced odds ratios equivalent to or slightly higher than the closest-site methods. Odds ratios obtained using the utility-wide average, but not the closest-site, approach also became progressively stronger in the weighted and subset analyses. A dose-response was seen between SAB and an exposure metric incorporating both TTHM concentration (utility-wide average approach) and personal ingestion, with SAB rates ranging from 8.3% to 13.7% (unweighted), 7.9% to 16.6% (variance weighted), and 6.6% to 23.1% (low-variance subset). Utility-wide average TTHM exposure assessment methods together with variance-based weights and subsets are relatively simple exposure assessment techniques, which may increase the epidemiologic usefulness of utility sampling records.

Illness and absenteeism among California highway patrol officers responding to hazardous material spills.

Highway patrol officers are the primary responders to hazardous material spills in California, yet little is known regarding the health effects resulting from this exposure. A historical cohort study of 993 California highway patrol officers who responded to hazardous material spills in 1984 was conducted. The records of officers who were exposed to acutely toxic chemicals were followed for the subsequent week to determine if they demonstrated more absenteeism or illness compared to officers who were not exposed to toxic chemicals. No significant differences in the frequency of absenteeism or illness was found between the two groups during the week following exposure. No indication was found that exposure to hazardous materials during a highway patrol spill response results in increased absenteeism.

Malformations in twins and their siblings, Norway, 1967-79.

During 1967-79 the population-based Medical Birth Registry of Norway registered 7,660 twin pairs (1% of births) born to 7,596 mothers, who gave birth to 6,608 additional infants (twin siblings). The total rate of malformations among twins (278.1/10,000) was not significantly different than among singletons (302.1/10,000), nor among twin siblings (314.8/10,000). By specific type of defect, twins had significantly higher rates than singletons of central nervous system (CNS) defects (Rate Ratio = 1.8) and cardiovascular defects (RR = 1.5). The twins also had a significantly low rate of congenital hip dislocation (RR = 0.4), which may explain the relatively low incidence of malformations in twins. Like-sex (LS) twins had a slightly higher rate of malformations than unlike-sex (US) twins (RR = 1.1), as well as a higher rate of CNS defects (RR = 3.0). The siblings also had a significantly increased rate of CNS defects compared to singletons (RR = 1.9), but not of cardiovascular defects (RR = 0.9). The results indicate that twins have elevated rates of at least some congenital malformations. The observations about CNS defects suggest common factors that can lead to either like-sex twinning, CNS defects, or both. The increased frequency of cardiovascular defects in twins appears to be associated with the biologic conditions of twinning.

Secular trends of neural tube defects by demographic subgroups in Norway, 1967-81.

The secular trends of NTDs by subgroups were investigated using data from the population-based Medical Birth Registry of Norway. During 1967-81, rates of total congenital malformations significantly increased by 4.1% annually. In contrast, there was an average annual decline of 1.6% in anencephaly rates and 0.4% in spina bifida rates. Annual rates of NTDs among twins decreased more (3.8%) than among singletons (1.6%). Females had an annual decline in rates (2.2%) that was greater than in males (0.7%). Separation of NTDs into two sub-groups based on the presence of multiple major malformations, revealed a significant decline of 2.1% annually in singles, whereas rates in multiples showed an increase of 3.3% annually. The different prevalence patterns revealed in various subgroups strongly suggest different etiologic entities. These should be further refined for elucidating etiologic factors. Furthermore, in prediction of current cases and evaluation of the effects of health services, the proportion of the various subgroups present should be considered.

Neural tube defects among twin births.

To obtain accurate, unbiased rates of neural tube defects (NTDs) in twins, we conducted a population-based study that included live births and fetal deaths in Los Angeles County, California, ascertaining cases by multiple methods. Twenty-eight twin cases yielded a prevalence-at-birth of 1.6/1,000 twin births, which is significantly higher than the singleton prevalence of 1.1/1,000 births. In twins compared with singletons, the prevalences of both encephalocele and anencephaly are increased, whereas spina bifida is decreased. The twin case male/female sex ratio (.55) is lower than the singleton case sex ratio (.77). Concordance is relatively low at 3.7%, but appears to be higher than recently reported recurrence risks in other low prevalence areas. Stillbirths were most common among female cases and like-sex twins. Our study tends to support proposed etiologic theories associating NTDs with females or monozygotic twins, or both. There is increasing evidence that the etiology of NTDs may differ in high and low prevalence areas. We suggest also that twins and singletons may differ in their response to etiologic factors. The variations among anencephaly, spina bifida, and encephalocele in their association with twinning suggest that there may be different factors that influence the development of each specific NTD. The noted differences among the malformations also indicate that some of the variation among results of other studies of NTDs and twinning may be due to case ascertainment. Including spina bifida cases would decrease the proportion of twins in a study population, while including anencephalics would increase the proportion. Importantly, ascertaining fetal deaths would increase the proportion of anencephalics and case females, so studies of NTDs that do not include fetal deaths will show fewer twins than expected. On the basis of our findings and those of Layde et al., excluding encephaloceles will also decrease the number of twins among NTD cases. When investigating etiologic hypotheses for NTDs, these potential biases must be recognized.

Moderate maternal and paternal alcohol consumption and the risk of spontaneous abortion.

Maternal alcoholism can lead to the fetal alcohol syndrome in offspring, but the effect of more moderate alcohol consumption during pregnancy remains an issue of concern. Therefore, we analyzed data from a large case-control study of spontaneous abortion (626 cases, 1,300 controls) that ascertained maternal alcohol consumption before and during pregnancy, as well as paternal consumption. Asking when in pregnancy alcohol consumption changed allowed us to calculate a weighted average of the amount consumed weekly during the first trimester. The odds ratio for consumption of seven or more drinks per week was 1.9 [95% confidence interval (CI) = 1.1-3.4] when adjusted for maternal smoking, passive smoking, and maternal age. Data were too sparse to examine higher consumption levels. There was some evidence that cases may have had less opportunity than controls to decrease consumption during their shorter pregnancies, potentially biasing the odds ratio upward. The adjusted odds ratio for any paternal alcohol consumption was 1.2 (CI = 0.93-1.5), with no dose-response effect seen. Among pregnancies in which the mother did not drink, there was no association with paternal drinking.

A population-based study of cancer incidence in twins and in children with congenital malformations or low birth weight, Norway, 1967-1980.

The incidence of childhood cancer in twins, in children with congenital malformations diagnosed at birth, and in children of low birth weight was investigated and compared with that in the total population of Norway born live from 1967-1979. Only the malformation group had a significantly increased rate of total cancer (28.3/100,000 person-years) compared with the population (14.6/100,000). The excess cancer appeared to be limited to children with Down's syndrome or a central nervous system defect, who most frequently developed leukemia or central nervous system tumors, respectively. The rates of total cancer in children of low birth weight (9.3/100,000) and in twins (13.0/100,000) were close to expected. However, twins had a significantly increased rate of renal cancer (rate ratio = 4.1). The documented associations between cancers and congenital malformations are suggestive of some common etiologic factors which warrant further studies for their identification and for elucidating possible means of prevention.

Employment in electronics manufacturing and risk of spontaneous abortion.

A large case-control study of environmental risk factors for spontaneous abortion was conducted among women living in Santa Clara County, California. Because of the prevalence of electronics production work within this population, a specialized questionnaire was administered to women who self-identified as electronics production workers. Spontaneous abortions were identified from pathology records, and controls were identified from birth certificates. The odds ratio for spontaneous abortion and any electronics production work was 0.94 (95% confidence interval = 0.58, 1.5). Odds ratios for the three main branches of electronics production (semiconductor fabrication, printed circuit board manufacturing, and assembly) were likewise near or below unity. Specific production activities with elevated odds ratios included semiconductor diffusion, parts encapsulation, soldering, and flux removal, although the numbers were small and none of the confidence intervals excluded unity. Limitations of this study included modest statistical power and a potential for nondifferential misclassification of exposures, both of which could bias findings toward the null.

The association of twinning and neural tube defects: studies in Los Angeles, California, and Norway.

Accurate, unbiased malformation rates in twins must be obtained unselectively from population-based studies that include livebirths and stillbirths after a thorough ascertainment of cases. This type of study was conducted in Los Angeles County, California, where 28 twins with a neural tube defect (NTD) were identified. The prevalence in twins (1.6/1,000) was significantly higher than in singletons (1.1/1,000). The study then was expanded to include population-based data from the Medical Birth Registry of Norway which has a comparable overall NTD prevalence (1.0/1,000) and twinning rate (2%). The combined material shows a higher prevalence of anencephaly and encephalocele but not of spina bifida in twins compared to singletons. The male/female ratios in total twin and singleton cases were comparable (0.8), but varied by specific defect. Like-sex twin females appeared at highest risk for NTD as well as for fetal death. This study supports theories which associate NTDs with monozygotic twins, either through developmental disruptions that cause susceptibility to environmental agents or through a common etiology. Furthermore, it suggests that twins and singletons differ in their response to etiologic factors for the development of NTDs and that the development of each type of NTD may be related to different factors.

On the cysteine and cystine content of proteins. Differences between intracellular and extracellular proteins.

Analysis of published data on the cysteine and half-cystine content of proteins indicates that most intracellular proteins may be classified as sulfhydryl proteins (those containing cysteine but little or no half-cystine) and that such sulfhydryl proteins have a low cysteine content. The mean systeine content found for 32 intracellular mammalian proteins was 1.6% and intracellular proteins of many bacteria have similar or lower values. Extracellular mammalian proteins are primarily disulfide proteins (those containing half-cystine but little or no cysteine) have a high half-cystine content, the mean value found for some 34 extracellular mammalian proteins being 4.1%. This is contrasted with many of the extracellular proteins from facultative bacteria which are cyst(e)ine-free proteins, being lacking in both cysteine and half-cystine. These and related observations are interpreted in terms of the evolution of life in a reducing atmosphere and the subsequent transition to an oxidizing environment. It is suggested that disulfide proteins evolved primarily after the accumulation of oxygen in the atmosphere.

Parental cigarette smoking and the risk of spontaneous abortion.

Although cigarette smoking is often considered a risk factor for spontaneous abortion, the epidemiologic literature is actually inconsistent. Therefore, the authors examined maternal and paternal smoking and maternal passive smoke exposure using data from a large case-control study of spontaneous abortion (626 cases and 1,300 controls) conducted in Santa Clara County, California, in 1986 and 1987. No excess risk of spontaneous abortion was seen in the 1% of women who smoked an average of more than 20 cigarettes per day in the first trimester. Moderate smokers (11-20 cigarettes per day) had a slightly elevated crude odds ratio of 1.3 (95% confidence interval 0.9-1.9), which was close to unity after adjustment for covariates. Paternal smoking showed a slight crude elevation for moderate and heavy smoking, but no association after adjustment. In contrast, maternal exposure to environmental tobacco smoke for 1 hour or more per day was associated with spontaneous abortion, even after adjustment (odds ratio = 1.5, 95% confidence interval 1.2-1.9). For both maternal direct and environmental exposure, the association appeared to be stronger in second-trimester abortions. Several studies have found stronger associations of smoking with late versus early abortions, perhaps reflecting smoking-associated placental insufficiency and fetal hypoxia.

Evidence for an association between environmental tobacco smoke exposure and birthweight: a meta-analysis and new data.

Because of the strong association of active smoking with fetal growth retardation, increasing interest has focused on whether there is also an association with exposure to environmental tobacco smoke (ETS). We examined this issue in a retrospective study and by conducting a review of the literature and data pooling. In our study, nonsmoking women with singleton livebirths born in 1986-87 (n = 992) provided information on exposure to ETS for 1 h or more per day and paternal smoking. The risk of low birthweight (LBW, < 2500 g) was not increased in infants of ETS-exposed women, but there was a somewhat increased risk for LBW at term (adjusted odds ratio [OR] 1.8, 95% confidence interval [CI] 0.6, 4.8) and small-for-gestational-age (< 10th percentile of weight; OR = 1.4, 95% CI = 0.8, 2.5). These results were in the range of 16 other studies in the literature that had odds ratios from 1.0 to 2.2. A weighted average of the results of all studies on LBW at term or small-for-gestational-age yielded a pooled estimate of 1.2 [95% CI = 1.1, 1.3] in nonsmoking women. The pooled estimate of mean birthweight indicated a decrement of 28 g with ETS exposure of nonsmoking women [95% CI = -41, -16], with a greater decrement (about 40 g) seen among more homogeneous studies.

Prenatal active or passive tobacco smoke exposure and the risk of preterm delivery or low birth weight.

We examined the association of exposure to environmental tobacco smoke with birth weight and gestational age in a large, prospective study. We also compared these endpoints between infants of active maternal smokers and those of non-smoking, non-ETS exposed women. Pregnant women were interviewed by telephone during the first trimester, and pregnancy outcome was determined for 99%. Among the 4,454 singleton live births that could be linked to their birth certificate, we confirmed increased risks of low birth weight and small for gestational age with heavier maternal smoking (> 10 cigarettes/day), as well as noting an increased risk for "very preterm" birth (< 35 weeks). These associations were generally stronger among infants of older (> or = 30 years) than those of younger mothers, as well as among non-whites. High environmental tobacco smoke exposure (> or = 7 hours/day in non-smokers) was moderately associated with low birth weight (adjusted odds ratio (AOR) 1.8, 95% confidence limits (95% CL) = 0.82, 4.1), preterm birth (AOR 1.6, 95% CL = 0.87, 2.9), and most strongly with very preterm birth (AOR 2.4, 95% CL = 1.0, 5.3). These associations were generally greater among non-whites than whites. The data support earlier studies suggesting that prenatal environmental tobacco smoke exposure, in addition to maternal smoking, affects infant health.