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Biomedical subjects

Michele Marcus

Publications and source records attributed to Michele Marcus.

At least 19 recordsLinked to original sources
PubMed2006

Validity of self-reported menstrual cycle length.

PURPOSE: Self-reported menstrual cycle length has been associated with host and environmental factors and chronic disease risk. The purpose of this study is to evaluate the validity of self-reported cycle length. METHODS: The authors assessed the agreement between a woman's self-reported "usual" cycle length at study onset with the mean of her observed cycle lengths from prospective daily diaries for 398 women aged 19 to 41 years in the Mount Sinai Study of Women Office Workers (1990 to 1994). RESULTS: Forty-three percent of women self-reported usual cycle lengths more than 2 days different from their mean length. When self-reported cycle length was categorized (<26, 26 to 35, and >35 days) and compared with mean cycle length, 21% of women were misclassified. Women who were older, married, and with higher income were more likely to have accurately reported their menstrual cycle length. Women who had short or long mean cycle lengths (lowest and highest quintile of length) were less likely to self-report accurately, and accuracy decreased monotonically with increasing cycle variability. CONCLUSIONS: These findings show considerable measurement error in self-reported cycle length, as well as describe population subgroups that report menstrual cycle length with the greatest accuracy.

Adult↗
PubMed2006

Keyboard use and musculoskeletal outcomes among computer users.

BACKGROUND: In this review, the epidemiological evidence examining associations between upper extremity musculoskeletal symptoms and disorders and keyboard use intensity (hours of computer use-per day or per-week) and computer user posture was explored. METHODS: An OVID Medline literature search was conducted to identify papers published in the peer-reviewed medical literature between 1966 and November, 2005. A total of 558 citations were found and reviewed. Those papers in which associations between musculoskeletal outcomes and (1) posture (ascertained by a study investigator) or (2) computer use, in units of hours-per-day, hours-per-week, or as a percent of work-time, were included in the review. RESULTS: Thirty-nine epidemiological studies examining associations between computer use and MSD outcomes were identified. While the observational epidemiological literature was heterogeneous, some trends did emerge. It appears that the most consistent finding was the association observed between hours keying and hand/arm outcomes. Associations between some postural effects and musculoskeletal outcomes may also be inferred from the literature. In particular, placing the keyboard below the elbow, limiting head rotation, and resting the arms appears to result in reduced risk of neck/shoulder outcomes. Minimizing ulnar deviation and keyboard thickness appears to result in reduced risk of hand/arm outcomes. CONCLUSIONS: Several methodological limitations, including non-representative samples, imprecise or biased measures of exposure and health outcome, incomplete control of confounding, and reversal of cause and effect, may contribute to the heterogeneity of observed results. Suggestions are made for improving the validity of future investigations.

Computer Peripherals↗
PubMed2006

Menstrual cycle characteristics: associations with fertility and spontaneous abortion.

BACKGROUND: Epidemiologists often use menstrual cycle patterns as indicators of endocrine function in environmental and occupational studies, yet few studies have considered whether menstrual cycle characteristics are associated with fertility or pregnancy outcome. METHODS: We prospectively studied 470 women to determine whether cycle length or bleed length were associated with fertility or spontaneous abortion. Women completed daily diaries with information on menstrual bleeding, intercourse, birth control use, and covariates. For each menstrual cycle, women collected at least 2 urine samples, which were assayed for human chorionic gonadotropin to define early pregnancies. Women were followed for 1 year or until the end of a clinical pregnancy. RESULTS: Cycles with lengths of 30 to 31 days preceded cycles with the highest fecundity. Shorter cycles were less likely to be followed by conception (fecundity ratio [FR] = 0.6; 95% confidence interval [CI] = 0.4-1.0). Compared with 30- to 31-day cycles, conceptions after shorter and longer cycles were more likely to be spontaneously aborted (for shorter cycles, odds ratio [OR] = 3.0 [95% CI = 0.9-9.6] and for longer cycles, OR = 3.0 [0.9-10.6]). Cycles with 5 days of menstrual bleeding had the highest fecundity. Cycles with up to 4 days of bleeding had lower fecundity (for bleed lengths of 4 days, FR = 0.5 [0.3-0.8] and for bleed lengths less than 4 days, FR = 0.6 [0.3-0.9]). Spontaneous abortion was less likely after bleeds greater than 5 days (OR = 0.4 [0.1-1.1]) when compared with 5-day bleeds. CONCLUSIONS: Menstrual cycle characteristics appear to be associated with fertility and spontaneous abortion.

Abortion, Spontaneous↗
PubMed2005

Menstrual function among women exposed to polybrominated biphenyls: a follow-up prevalence study.

BACKGROUND: Alteration in menstrual cycle function is suggested among rhesus monkeys and humans exposed to polybrominated biphenyls (PBBs) and structurally similar polychlorinated biphenyls (PCBs). The feedback system for menstrual cycle function potentially allows multiple pathways for disruption directly through the hypothalamic-pituitary-ovarian axis and indirectly through alternative neuroendocrine axes. METHODS: The Michigan Female Health Study was conducted during 1997-1998 among women in a cohort exposed to PBBs in 1973. This study included 337 women with self-reported menstrual cycles of 20-35 days (age range: 24-56 years). Current PBB levels were estimated by exponential decay modeling of serum PBB levels collected from 1976-1987 during enrollment in the Michigan PBB cohort. Linear regression models for menstrual cycle length and the logarithm of bleed length used estimated current PBB exposure or enrollment PBB exposure categorized in tertiles, and for the upper decile. All models were adjusted for serum PCB levels, age, body mass index, history of at least 10% weight loss in the past year, physical activity, smoking, education, and household income. RESULTS: Higher levels of physical activity were associated with shorter bleed length, and increasing age was associated with shorter cycle length. Although no overall association was found between PBB exposure and menstrual cycle characteristics, a significant interaction between PBB exposures with past year weight loss was found. Longer bleed length and shorter cycle length were associated with higher PBB exposure among women with past year weight loss. CONCLUSION: This study suggests that PBB exposure may impact ovarian function as indicated by menstrual cycle length and bleed length. However, these associations were found among the small number of women with recent weight loss suggesting either a chance finding or that mobilization of PBBs from lipid stores may be important. These results should be replicated with larger numbers of women exposed to similar lipophilic compounds.

Adult↗
PubMed2005

Modeling menstrual cycle length using a mixture distribution.

In reproductive health studies, epidemiologists are often interested in examining the effects of covariates on menstrual cycle length which is a convenient, noninvasive measure of women's ovarian and reproductive function. Previous literature (Harlow and Zeger, 1991) suggests that the distribution of cycle length is a mixture of a major symmetric distribution and a component featuring a long right tail. Motivated by the shape of this marginal distribution, we propose a mixture distribution for cycle length, representing standard cycles from a Normal distribution and nonstandard cycles from a shifted Weibull distribution. The parameters are estimated using an estimating equation derived from the score function of an independence working model. The fitted mixture distribution agrees well with the distribution estimated using nonparametric approaches. We propose two measures to help determine whether a cycle is standard or nonstandard, developing tools necessary to identify characteristics of the menstrual cycles that are biologically indicative of ovarian dysfunction. We model the effect of a woman's age on the mean and variation of both standard and nonstandard cycle lengths using multiple measurements of women.

Adult↗
PubMed2005

CYP17 genotype predicts serum hormone levels among pre-menopausal women.

BACKGROUND: CYP17, which encodes cytochrome P450c17alpha, mediates both steroid 17alpha-hydroxylase and 17,20-lyase activities, and is essential for the production of glucocorticoids and sex steroids. There is evidence that a common polymorphism in CYP17 (T27C) is associated with estrogen levels, making it a potential marker of disease risk. METHODS: This is the first study to examine the relationship between CYP17 and estradiol (E2) using serum sampled exclusively from the early follicular phase of the menstrual cycle. We assessed the relationship between CYP17 and serum hormone levels, menstrual cycle length, bleed length, and age at menarche in 164 pre-menopausal women. RESULTS: Among women with body mass index (BMI) < or =25 kg/m2, those with the TC and CC genotypes had 19 and 42% higher E2 (P for trend 0.007) and 14 and 30% higher dehydroepiandrosterone sulphate respectively (P for trend 0.10) than women with the TT genotype. Androstenedione levels did not differ between genotypes. Among women with BMI >25 kg/m2, hormone levels did not differ by genotype. Women with the C allele were also more likely to have menstrual cycle lengths <27 days [odds ratio (OR) for TC=2.36, 95% confidence interval (CI)=1.24-4.52; OR for CC=5.59, 95% CI=1.53-20.43 compared to TT]. CYP17 genotype was not associated with menstrual bleed length or age at menarche. CONCLUSION: The CYP17 T27C polymorphism may be a marker of endocrine function.

Adolescent↗
PubMed2005

Diet and physical activity behaviors among Americans trying to lose weight: 2000 Behavioral Risk Factor Surveillance System.

OBJECTIVE: To examine the prevalence and correlates of trying to lose weight among U.S. adults, describe weight loss strategies, and assess attainment of recommendations for weight control (eating fewer calories and physical activity). RESEARCH METHODS AND PROCEDURES: This study used the Behavioral Risk Factor Surveillance System, a state-based telephone survey of adults > or =18 years of age (N = 184,450) conducted in the 50 states, the District of Columbia, and Puerto Rico in 2000. RESULTS: The prevalence of trying to lose weight was 46% (women) and 33% (men). Women reported trying to lose weight at a lower BMI than did men; 60% of overweight women were trying to lose weight, but men did not reach this level until they were obese. Adults who had a routine physician checkup in the previous year and reported medical advice to lose weight vs. checkup and no medical advice to lose weight had a higher prevalence of trying to lose weight (81% women and 77% men vs. 41% women and 28% men, respectively). The odds of trying to lose weight increased as years of education increased. Among respondents who were trying to lose weight, approximately 19% of women and 22% of men reported using fewer calories and > or =150 min/wk leisure-time physical activity. DISCUSSION: A higher percentage of women than men were trying to lose weight; both sexes used similar weight loss strategies. Education and medical advice to lose weight were strongly associated with trying to lose weight. Most persons trying to lose weight were not using minimum recommended weight loss strategies.

Adolescent↗
PubMed2005

Job strain and risk of musculoskeletal symptoms among a prospective cohort of occupational computer users.

OBJECTIVES: Most previous studies of the association between psychosocial stress and musculoskeletal illness among computer users have been cross-sectional and have yielded inconsistent results. The association between a measure of psychosocial stress, "job strain", and incident neck-shoulder and arm-hand musculoskeletal symptoms was investigated among recently hired computer users. METHODS: The participants worked for one of several large employers and were followed prospectively for 6 months. The "job demands" and "decision latitude" subscales of the Job Content Questionnaire were used to estimate the job-strain quadrants and a ratio measure of job strain which was subsequently categorized. Incident musculoskeletal symptoms were obtained with weekly diaries. Proportional hazards models were used to estimate associations between job strain and incident musculoskeletal symptoms. RESULTS: Those in the high-strain quadrant were at increased risk of neck-shoulder symptoms [hazard ratio (HR) 1.65, 95% confidence interval (95% CI) 0.91-2.99] when compared with those in the low-strain quadrant. Those in the highest strain-ratio category were also at increased risk of neck-shoulder symptoms when compared with those in the lowest strain-ratio category (HR 1.52, 95% CI 0.88-2.62). Modification by previous years of computer use was observed, with an elevated risk observed for those in the highest job-strain ratio category who also had low previous computer use (HR 3.16, 95% CI 1.25-8.00). There did not appear to be an association between either measure of job strain and incident arm-hand symptoms. CONCLUSIONS: In this cohort, workers who reported high job strain were more likely to develop neck-shoulder symptoms.

Adolescent↗
PubMed2004

Time to menopause in relation to PBBs, PCBs, and smoking.

OBJECTIVES: Because halogenated biphenyl exposure is suspected to disrupt endocrine function, we assessed time to menopause in women aged 24 years and older who were exposed orally to polybrominated biphenyls (PBBs) and polychlorinated biphenyls (PCBs) (n = 874). We also examined smoking in relation to menopause. METHODS: To define menopausal status, women were interviewed in 1997 and asked whether they had had any menstrual periods in the previous year, why their menstrual periods had stopped (e.g. surgery), and age at their last menstrual period. Serum PBB and PCB taken at enrollment (1976-1978) into the Michigan PBB registry was used as the measure of halogenated biphenyl exposure. Women whose menopause occurred before their PBB exposure were excluded. Proportional hazard modeling was used to analyze the "risk" for menopause in relation to exposure. Premenopausal women contributed person-time until their interview date, at which time they were censored. RESULTS: We did not find an association between either PBB or PCB exposure and time to menopause. Women who were current smokers had a shorter time to menopause than never smokers (menopause ratio 2.02, 95% C.I. 1.21-3.37). Time to menopause was shortest among women who reported started smoking when they were <18 years of age, smoked at least 20 cigarettes per day, or had at least 10 pack-years of smoking.

Adult↗
PubMed2004

Epidemiology of musculoskeletal disorders among computer users: lesson learned from the role of posture and keyboard use.

Reports in the scientific literature and lay press have suggested that computer users are at increased risk of upper extremity musculoskeletal disorders (MSDs). Early studies often found elevated rates of MSD outcomes among keyboard users when compared to non-users. Attention soon focused on specific aspects of keyboard work that might be responsible for the observed rate increase. In this review, the epidemiological evidence examining associations between MSD outcomes and computer user posture and keyboard use intensity (hours of computer use per day or per week) are examined. Results of epidemiological studies of posture and MSD outcomes have not been entirely consistent. Reasons for the inconsistency in results include cross-sectional study design (with possible failure to assure that measured exposure preceded health effect), imprecision of posture measures used, and difficulties involved in analyzing multiple related variables. Despite the inconsistencies, it appears from the literature that posture is an independent risk factor of modest magnitude for MSDs among computer users. It appears that lowering the height of the keyboard to or below the height of the elbow and resting the arms on the desk surface or chair armrests is associated with reduced risk of neck and shoulder MSDs. Results of epidemiological studies examining computer use (hours keying per day or per week) are more consistent than those examining posture, although some inconsistency is observed. Reasons for the inconsistency include possible selective survival bias resulting from cross-sectional study design, differences in exposure categorization, and possible interaction with other exposure variables. Overall, the literature shows that daily or weekly hours of computer use is more consistently associated with hand and arm MSDs than with neck and shoulder MSDs.

Computers↗
PubMed2003

Polybrominated biphenyl exposure and benign breast disease in a cohort of US women.

PURPOSE: We examined the relation between serum polybrominated biphenyl (PBB) levels and the risk of benign breast disease in a cohort of Michigan women unintentionally exposed to PBBs in 1973 and interviewed in 1997. METHODS: We used extended Cox models to generate adjusted hazard ratios; models included polychlorinated biphenyls (PCBs) and risk factors for benign breast disease reported in the literature. RESULTS: Two hundred fourteen (23%) of 951 women reported benign breast disease diagnosed by a physician. Compared with women with low PBB exposure, benign breast disease was not reported more frequently among those with moderate (>1-12 parts per billion [ppb]), (odds ratio [OR] 1.08, 95% confidence interval [CI] = 0.80-1.45), or high (>12 ppb), (OR 0.79, 95% CI = 0.46-1.38) PBB exposure. PCB exposure was also not associated with self-reported physician-diagnosed benign breast disease. Age, smoking, and annual number of health-care provider visits were significantly associated with benign breast disease. CONCLUSIONS: Our analysis did not demonstrate an association between serum PBB level and self- reported physician-diagnosed benign breast disease. We did observe an increased risk of benign breast disease for women who smoked, an association that has not been consistently found in previous studies.

Adolescent↗
PubMed2003

An occupational reproductive research agenda for the third millennium.

There is a significant public health concern about the potential effects of occupational exposure to toxic substances on reproductive outcomes. Several toxicants with reported reproductive and developmental effects are still in regular commercial or therapeutic use and thus present potential exposure to workers. Examples of these include heavy metals, organic solvents, pesticides and herbicides, and sterilants, anesthetic gases, and anticancer drugs used in health care. Many other substances are suspected of producing reproductive or developmental toxicity but lack sufficient data. Progress has been limited in identifying hazards and quantifying their potencies and in separating the contribution of these hazards from other etiologic factors. Identifying the causative agents, mechanisms by which they act, and any potential target populations, present the opportunity to intervene and protect the reproductive health of workers. The pace of laboratory studies to identify hazards and to underpin the biologic plausibility of effects in humans has not matched the pace at which new chemicals are introduced into commerce. Though many research challenges exist today, recent technologic and methodologic advances have been made that allow researchers to overcome some of these obstacles. The objective of this article is to recommend future directions in occupational reproductive health research. By bridging interdisciplinary gaps, the scientific community can work together to improve health and reduce adverse outcomes.

Communication↗
PubMed2002

A prospective study of computer users: I. Study design and incidence of musculoskeletal symptoms and disorders.

BACKGROUND: A prospective study of computer users was performed to determine the occurrence of and evaluate risk factors for neck or shoulder (N/S) and hand or arm (H/A) musculoskeletal symptoms (MSS) and disorders (MSD). METHODS: Individuals (n = 632) newly hired into jobs requiring > or = 15 hr/week of computer use were followed for up to 3 years. At study entry, workstation dimensions and worker postures were measured and medical and psychosocial risk factors were assessed. Daily diaries were used to document work practices and incident MSS. Those reporting MSS were examined for specific MSD. Incidence rates of MSS and MSD were estimated with survival analysis. Cox regression models were used to evaluate associations between participant characteristics at entry and MSS and MSD. RESULTS: The annual incidence of N/S MSS was 58 cases/100 person-years and of N/S MSD was 35 cases/100 person-years. The most common N/S MSD was somatic pain syndrome. The annual incidence of H/A MSS was 39 cases/100 person-years and of H/A MSD was 21 cases/100 person-years. The most common H/A disorder was deQuervain's tendonitis. Forty-six percent of N/S and 32% of H/A MSS occurred during the first month of follow-up. Gender, age, ethnicity, and prior history of N/S pain were associated with N/S MSS and MSD. Gender, prior history of H/A pain, prior computer use, and children at home were associated with either H/A MSS or MSD. CONCLUSIONS: H/A and N/S MSS and MSD were common among computer users. More than 50% of computer users reported MSS during the first year after starting a new job.

Adult↗
PubMed2002

A prospective study of computer users: II. Postural risk factors for musculoskeletal symptoms and disorders.

BACKGROUND: Despite widespread recommendations regarding posture during computer use, associations between specific postures and musculoskeletal health are not well characterized. METHODS: Six hundred and thirty-two newly hired computer users were followed prospectively to evaluate associations between posture and neck or shoulder (N/S) and hand or arm (H/A) musculoskeletal symptoms and musculoskeletal disorders. Participants' postures were measured at entry and they reported symptoms on weekly diaries. Participants reporting symptoms were examined for specific disorders. Multivariate Cox regression models were used to estimate associations between postural variables and risk of symptoms and disorders, controlling for confounding variables. RESULTS: Keying with an inner elbow angle > 121 degrees, greater downward head tilt, and presence of armrests on the participants chair were associated with lower risk of N/S symptoms or N/S disorders. Keying with elbow height below the height of the "J" key and the presence of a telephone shoulder rest were associated with a greater risk of N/S symptoms or N/S disorders. Horizontal location of the "J" key > 12 cm from the edge of the desk was associated with a lower risk of H/A symptoms and H/A disorders. Use of a keyboard with the "J" key > 3.5 cm above the table surface, key activation force > 48 g, and radial wrist deviation of > 5 degrees while using a mouse was associated with a greater risk of H/A symptoms or H/A disorders. The number of hours keying/week was associated with H/A symptoms and disorders. CONCLUSIONS: The results suggest that the risk of musculoskeletal symptoms and musculoskeletal disorders may be reduced by encouraging specific seated postures.

Arm↗
PubMed2002

Stature and pubertal stage assessment in American boys: the 1988-1994 Third National Health and Nutrition Examination Survey.

PURPOSE: To describe current stature and pubertal development in North American boys, and to compare these measures with measures observed approximately 30 years ago. METHODS: We analyzed data (i.e., height, weight, and Tanner Stage) from the Third National Health and Nutrition Examination Survey (NHANES III), conducted between 1988-1994, and compared it to the National Health Examination Survey, Cycles II and III (HES II/III), conducted from 1963-1965 and 1966-1970. The surveys included physical examination and questionnaire components, employed cross-sectional designs, and are nationally representative. We used logistic regression to calculate median age at onset of pubertal stages. RESULTS: NHANES III included 2481 boys aged 8 to 18 years. HES II comprised 3010 boys aged 8-11 years and HES III comprised 3514 boys aged 12-17 years. The mean heights of the oldest boys in both surveys did not differ significantly; however, at younger ages, boys in the more recent survey were taller (average height difference among those aged 8-14 years was 2.0 cm). Boys in NHANES III were also heavier and had higher body mass index than those in HES II/III. The median estimated ages of onset of pubertal stages in NHANES III were 9.9, 12.2, 13.6, and 15.8 years for genital stages 2-5, respectively, and 11.9, 12.6, 13.6, and 15.7 years for pubic hair stages 2-5, respectively. For some stages, the median estimated age of onset of puberty was earlier among boys in NHANES III than among those in HES III. CONCLUSIONS: Differences in mean height at young ages, but not at older ages, suggest that the rate of growth among boys in NHANES III was faster than that of boys in the earlier surveys. This finding, coupled with the finding of earlier ages of onset of some pubertal stages, suggests that boys of this generation may be maturing more rapidly than did boys in the past.

Adolescent↗
PubMed2002

Growth in girls exposed in utero and postnatally to polybrominated biphenyls and polychlorinated biphenyls.

BACKGROUND: Accidental contamination with polybrominated biphenyls (PBBs) of the Michigan food supply in 1973 led to the exposure of more than 4000 individuals and to formation of the PBB cohort registry (1976-1979). At enrollment, measurements were taken of serum PBB and polychlorinated biphenyl (PCB), possible endocrine disrupting chemicals. METHODS: We examined the association of estimated PBB and PCB exposure during pregnancy with current height and weight in 308 daughters, 5-24 years of age (mean age 15.2 years), born to women in the cohort. We estimated prenatal PBB exposure using maternal enrollment serum PBB and a model of PBB elimination. Prenatal PCB exposure was estimated using maternal enrollment serum PCB because background-level exposure through diet was ongoing. Self-reported height and weight were obtained from a 1997-1998 health survey. RESULTS: We found no association between prenatal PBB exposure and either daughter's current height or daughter's weight adjusted for height; however, prenatal PCB exposure above 5 parts per billion was associated with reduced weight adjusted for height. Exposure through breastfeeding did not modify the association. CONCLUSIONS: Mothers with PCB levels above the median had daughters whose current weights were 11 pounds lower than that of the daughters whose mothers had levels below the median. This study provides evidence that prenatal exposure to PCBs may affect growth.

Adolescent↗