Janet W. Rich-Edwards

A Prospective Study of Walking as Compared with Vigorous Exercise in the Prevention of Coronary Heart Disease in Women

BACKGROUND The role of walking, as compared with vigorous exercise, in the prevention of coronary heart disease remains controversial, and data for women on this topic are sparse. METHODS We prospectively examined the associations between the score for total physical activity, walking, and vigorous exercise and the incidence of coronary events among 72,488 female nurses who were 40 to 65 years old in 1986. Participants were free of diagnosed cardiovascular disease or cancer at the time of entry and completed serial detailed questionnaires about physical activity. During eight years of follow-up, we documented 645 incident coronary events (nonfatal myocardial infarction or death from coronary disease). RESULTS There was a strong, graded inverse association between physical activity and the risk of coronary events. As compared with women in the lowest quintile group for energy expenditure (expressed as the metabolic-equivalent [MET] score), women in increasing quintile groups had age-adjusted relative risks of 0.77, 0.65, 0.54, and 0.46 for coronary events (P for trend <0.001). In multivariate analyses, the inverse gradient remained strong (relative risks, 0.88, 0.81, 0.74, and 0.66 for women in increasing quintile groups as compared with those in the lowest quintile group; P for trend=0.002). Walking was inversely associated with the risk of coronary events; women in the highest quintile group for walking, who walked the equivalent of three or more hours per week at a brisk pace, had a multivariate relative risk of 0.65 (95 percent confidence interval, 0.47 to 0.91) as compared with women who walked infrequently. Regular vigorous exercise (> or =6 MET) was associated with similar risk reductions (30 to 40 percent). Sedentary women who became active in middle adulthood or later had a lower risk of coronary events than their counterparts who remained sedentary. CONCLUSIONS These prospective data indicate that brisk walking and vigorous exercise are associated with substantial and similar reductions in the incidence of coronary events among women.

Birth weight and risk of type 2 diabetes: A systematic review

CONTEXT Low birth weight is implicated as a risk factor for type 2 diabetes. However, the strength, consistency, independence, and shape of the association have not been systematically examined. OBJECTIVE To conduct a quantitative systematic review examining published evidence on the association of birth weight and type 2 diabetes in adults. DATA SOURCES AND STUDY SELECTION Relevant studies published by June 2008 were identified through literature searches using EMBASE (from 1980), MEDLINE (from 1950), and Web of Science (from 1980), with a combination of text words and Medical Subject Headings. Studies with either quantitative or qualitative estimates of the association between birth weight and type 2 diabetes were included. DATA EXTRACTION Estimates of association (odds ratio [OR] per kilogram of increase in birth weight) were obtained from authors or from published reports in models that allowed the effects of adjustment (for body mass index and socioeconomic status) and the effects of exclusion (for macrosomia and maternal diabetes) to be examined. Estimates were pooled using random-effects models, allowing for the possibility that true associations differed between populations. DATA SYNTHESIS Of 327 reports identified, 31 were found to be relevant. Data were obtained from 30 of these reports (31 populations; 6090 diabetes cases; 152 084 individuals). Inverse birth weight-type 2 diabetes associations were observed in 23 populations (9 of which were statistically significant) and positive associations were found in 8 (2 of which were statistically significant). Appreciable heterogeneity between populations (I(2) = 66%; 95% confidence interval [CI], 51%-77%) was largely explained by positive associations in 2 native North American populations with high prevalences of maternal diabetes and in 1 other population of young adults. In the remaining 28 populations, the pooled OR of type 2 diabetes, adjusted for age and sex, was 0.75 (95% CI, 0.70-0.81) per kilogram. The shape of the birth weight-type 2 diabetes association was strongly graded, particularly at birth weights of 3 kg or less. Adjustment for current body mass index slightly strengthened the association (OR, 0.76 [95% CI, 0.70-0.82] before adjustment and 0.70 [95% CI, 0.65-0.76] after adjustment). Adjustment for socioeconomic status did not materially affect the association (OR, 0.77 [95% CI, 0.70-0.84] before adjustment and 0.78 [95% CI, 0.72-0.84] after adjustment). There was no strong evidence of publication or small study bias. CONCLUSION In most populations studied, birth weight was inversely related to type 2 diabetes risk.

A Nearly Continuous Measure of Birth Weight for Gestational Age Using a United States National Reference

BackgroundFully understanding the determinants and sequelae of fetal growth requires a continuous measure of birth weight adjusted for gestational age. Published United States reference data, however, provide estimates only of the median and lowest and highest 5th and 10th percentiles for birth weight at each gestational age. The purpose of our analysis was to create more continuous reference measures of birth weight for gestational age for use in epidemiologic analyses.MethodsWe used data from the most recent nationwide United States Natality datasets to generate multiple reference percentiles of birth weight at each completed week of gestation from 22 through 44 weeks. Gestational age was determined from last menstrual period. We analyzed data from 6,690,717 singleton infants with recorded birth weight and sex born to United States resident mothers in 1999 and 2000.ResultsBirth weight rose with greater gestational age, with increasing slopes during the third trimester and a leveling off beyond 40 weeks. Boys had higher birth weights than girls, later born children higher weights than firstborns, and infants born to non-Hispanic white mothers higher birth weights than those born to non-Hispanic black mothers. These results correspond well with previously published estimates reporting limited percentiles.ConclusionsOur method provides comprehensive reference values of birth weight at 22 through 44 completed weeks of gestation, derived from broadly based nationwide data. Other approaches require assumptions of normality or of a functional relationship between gestational age and birth weight, which may not be appropriate. These data should prove useful for researchers investigating the predictors and outcomes of altered fetal growth.

Adolescent body mass index and infertility caused by ovulatory disorder

OBJECTIVE Our aim was to examine the association between body mass index at age 18 and subsequent primary ovulatory infertility. STUDY DESIGN A nested case-control study was conducted within a cohort of 116,678 female registered nurses residing in 14 U.S. states. Cases comprised 2527 married nulliparous nurses unable to become pregnant for at least 1 year because of ovulatory disorder; controls comprised 46,718 married parous nurses with no history of infertility. The risk of ovulatory infertility for women at different levels of body mass index at age 18 was compared with that for women whose body mass index at age 18 was 20 to 21.9 (median for the cohort). Logistic regression was used to adjust for age at infertility or first birth, year of birth, age at menarche, physical activity during ages 18 to 22, smoking at ages 15 to 19, ethnicity, alcohol use at ages 18 to 22, use of oral contraceptives before age 22, and diagnosis of diabetes mellitus. RESULTS Multivariate relative risks for infertility were: 1.2 (body mass index < 16), 1.1 (body mass index 16 to 17.9), 1.0 (body mass index 18 to 19.9), 1.0 (referent body mass index 20 to 21.9), 1.1 (body mass index 22 to 23.9), 1.3 (body mass index 24 to 25.9), 1.7 (body mass index 26 to 27.9), 2.4 (body mass index 28 to 29.9), 2.7 (body mass index 30 to 31.9), and 2.7 (body mass index > or = 32). The relative risks for all categories of body mass index above 23.9 were statistically significantly elevated. Greater body mass index at age 18 was a predictor of ovulatory infertility in women with and without a diagnosis of polycystic ovary syndrome. CONCLUSION These findings suggest that elevated body mass index at age 18, even at levels lower than those considered to be obese, is a risk factor for subsequent ovulatory infertility.

Maternal Fish Consumption, Hair Mercury, and Infant Cognition in a U.S. Cohort.

Fish and other seafood may contain organic mercury but also beneficial nutrients such as n-3 polyunsaturated fatty acids. We endeavored to study whether maternal fish consumption during pregnancy harms or benefits fetal brain development. We examined associations of maternal fish intake during pregnancy and maternal hair mercury at delivery with infant cognition among 135 mother–infant pairs in Project Viva, a prospective U.S. pregnancy and child cohort study. We assessed infant cognition by the percent novelty preference on visual recognition memory (VRM) testing at 6 months of age. Mothers consumed an average of 1.2 fish servings per week during the second trimester. Mean maternal hair mercury was 0.55 ppm, with 10% of samples > 1.2 ppm. Mean VRM score was 59.8 (range, 10.9–92.5). After adjusting for participant characteristics using linear regression, higher fish intake was associated with higher infant cognition. This association strengthened after adjustment for hair mercury level: For each additional weekly fish serving, offspring VRM score was 4.0 points higher [95% confidence interval (CI), 1.3 to 6.7]. However, an increase of 1 ppm in mercury was associated with a decrement in VRM score of 7.5 (95% CI, –13.7 to –1.2) points. VRM scores were highest among infants of women who consumed > 2 weekly fish servings but had mercury levels ≤1.2 ppm. Higher fish consumption in pregnancy was associated with better infant cognition, but higher mercury levels were associated with lower cognition. Women should continue to eat fish during pregnancy but choose varieties with lower mercury contamination.

Sociodemographic predictors of antenatal and postpartum depressive symptoms among women in a medical group practice

Objective: Data are scarce regarding the sociodemographic predictors of antenatal and postpartum depression. This study investigated whether race/ethnicity, age, finances, and partnership status were associated with antenatal and postpartum depressive symptoms. Setting: 1662 participants in Project Viva, a US cohort study. Design: Mothers indicated mid-pregnancy and six month postpartum depressive symptoms on the Edinburgh postpartum depression scale (EPDS). Associations of sociodemographic factors with odds of scoring >12 on the EPDS were estimated. Main results: The prevalence of depressive symptoms was 9% at mid-pregnancy and 8% postpartum. Black and Hispanic mothers had a higher prevalence of depressive symptoms compared with non-Hispanic white mothers. These associations were explained by lower income, financial hardship, and higher incidence of poor pregnancy outcome among minority women. Young maternal age was associated with greater risk of antenatal and postpartum depressive symptoms, largely attributable to the prevalence of financial hardship, unwanted pregnancy, and lack of a partner. The strongest risk factor for antenatal depressive symptoms was a history of depression (OR = 4.07; 95% CI 3.76, 4.40), and the strongest risk for postpartum depressive symptoms was depressive symptoms during pregnancy (6.78; 4.07, 11.31) or a history of depression before pregnancy (3.82; 2.31, 6.31). Conclusions: Financial hardship and unwanted pregnancy are associated with antenatal and postpartum depressive symptoms. Women with a history of depression and those with poor pregnancy outcomes are especially vulnerable to depressive symptoms during the childbearing year. Once these factors are taken in account, minority mothers have the same risk of antenatal and postpartum depressive symptoms as white mothers.

Reproducibility and Validity of Maternal Recall of Pregnancy-related Events

We assessed the reproducibility and validity of a questionnaire that asks mothers to recall pregnancy-related events from thirty or more years ago. Among 146 women who completed the questionnaire twice, responses were highly reproducible for pre-pregnancy height and weight (r = 0.95), pregnancy complications (r = 0.74), substance use (r = 0.80), preterm delivery (r = 0.82), birthweight (r = 0.94), and breastfeeding (r = 0.89). Among 154 women whose questionnaire responses were compared to data collected during their pregnancies, recall was highly accurate for height (r = 0.90), pre-pregnancy weight (r = 0.86), birthweight (r = 0.91), and smoking (sensitivity = 0.86, specificity = 0.94). These findings suggest that long-term maternal recall is both reproducible and accurate for many factors related to pregnancy and delivery.

Racial/Ethnic Differences in Early-Life Risk Factors for Childhood Obesity

OBJECTIVE: By the preschool years, racial/ethnic disparities in obesity prevalence are already present. The objective of this study was to examine racial/ethnic differences in early-life risk factors for childhood obesity. METHODS: A total of 1343 white, 355 black, and 128 Hispanic mother–child pairs were studied in a prospective study. Mothers reported childs race/ethnicity. The main outcome measures were risk factors from the prenatal period through 4 years old that are known to be associated with child obesity. RESULTS: In multivariable models, compared with their white counterparts, black and Hispanic children exhibited a range of risk factors related to child obesity. In pregnancy, these included higher rates of maternal depression (odds ratio [OR]: 1.55 for black, 1.89 for Hispanic); in infancy more rapid weight gain (OR: 2.01 for black, 1.75 for Hispanic), more likely to introduce solid foods before 4 months of age (OR: 1.91 for black, 2.04 for Hispanic), and higher rates of maternal restrictive feeding practices (OR: 2.59 for black, 3.35 for Hispanic); and after 2 years old, more televisions in their bedrooms (OR: 7.65 for black, 7.99 for Hispanic), higher intake of sugar-sweetened beverages (OR: 4.11 for black, 2.48 for Hispanic), and higher intake of fast food (OR: 1.65 for black, 3.14 for Hispanic). Black and Hispanic children also had lower rates of exclusive breastfeeding and were less likely to sleep at least 12 hours/day in infancy. CONCLUSIONS: Racial/ethnic differences in risk factors for obesity exist prenatally and in early childhood. Racial/ethnic disparities in childhood obesity may be determined by factors that operate at the earliest stages of life.

Physical Activity, Body Mass Index, and Ovulatory Disorder Infertility

Few studies have examined whether activity and adiposity levels typical of American women affect their risk of ovulatory disorder infertility, and none has examined moderate and vigorous intensity exercise separately. We investigated these associations in the Nurses’ Health Study II, comparing prospectively collected data on adiposity and activity for 830 cases of incident ovulatory infertility and 26,125 pregnancies. We observed a U-shaped association between body mass index (BMI) and relative risk of ovulatory infertility, with increased risk for BMI below 20.0 or above 24.0 kg/m2. On the basis of the BMI distribution of U.S. women, these findings suggest that 12% (95% confidence interval = 7–20%) of ovulatory infertility in the U.S. may be attributable to underweight (BMI <20.0) and 25% (95% CI = 20–31%) to overweight (BMI ≥25.0). An increase in vigorous activity (but not moderate activity) was associated with reduced relative risk of ovulatory infertility. Each hour per week of vigorous activity was associated with a 7% (95% CI = 4–10%) lower relative risk of ovulatory infertility. After adjustment for BMI, a 5% (95% CI = 2–8%) reduction in relative risk per hour of weekly activity remained. These data suggest that, among American women, more ovulatory infertility is attributable to overweight and a sedentary lifestyle than to underweight and overexertion.

Decline in fish consumption among pregnant women after a national mercury advisory

OBJECTIVE A well-publicized January 2001 federal advisory recommended that pregnant women limit consumption of certain fish because of concerns about mercury contamination. We endeavored to estimate the extent to which pregnant women changed fish consumption habits after dissemination of this national advisory. METHODS We performed interrupted time series analysis of data from a cohort of pregnant women (2235 who completed at least one dietary questionnaire) visiting obstetric offices in a multispecialty group practice in eastern Massachusetts, surveyed before the advisory from April 1999 through December 2000 and after the advisory from April 2001 through February 2002. Main outcome measures were consumption of total fish and of four fish types: canned tuna, dark meat fish, shellfish, and white meat fish. Subjects reported fish consumption on semiquantitative food frequency questionnaires administered at each trimester of pregnancy. RESULTS We observed diminished consumption of dark meat fish, canned tuna, and white meat fish after the national mercury advisory. These decreases resulted in a reduction in total fish consumption of approximately 1.4 servings per month (95% confidence interval 0.7, 2.0) from December 2000 to April 2001, with ongoing declines through the end of the study period. There was no change in shellfish intake. CONCLUSION After dissemination of federal recommendations, pregnant women in this cohort reported reduced consumption of fish, including tuna, dark meat fish, and white meat fish. Because these fish may confer nutritional benefits to mother and infant, public health implications of these changes remain unclear.