Timing of menopause, reproductive years, and bone mineral density: a cross-sectional study of postmenopausal Japanese women

Age at menopause has been found to be associated positively with bone mineral density, and age at menarche has been found to be associated negatively with bone mineral density. However, there have been few studies on the relations of timing of menopause and length of the reproductive period with bone mineral density. The purpose of this study was to examine the relations of timing of menopause and reproductive years (calculated as age at menopause minus age at menarche) with mineral density of the second metacarpal bone in postmenopausal Japanese women. The study population consisted of 1,035 naturally menopausal women aged 40-70 years who were screened in 1996-1997. Using computed x-ray densitometry, the authors measured bone mineral density by analyzing radiographic films of the right second metacarpal bone. Using the women with early menopause (age < 49 years) as the reference group and adjusting for age, subjects with late menopause were at decreased risk for low bone mineral density (odds ratio (OR) = 0.69, 95% confidence interval (CI) 0.49-0.97). After adjustment for additional covariates (grip strength, physical activity, body mass index, smoking, and calcium intake), the association was unchanged (OR = 0.70, 95% CI 0.50-0.99). Postmenopausal women with more reproductive years (> or = 40 years) were at decreased risk for low bone mineral density compared with those with fewer reproductive years, after adjustment for age (OR = 0.73, 95% CI 0.40-1.30) and potentially confounding factors (OR = 0.76, 95% CI 0.41-1.37); the p-value for trend was not statistically significant. In multiple linear regression analysis, early menopause and fewer reproductive years were independent predictors of low bone mineral density. In this study, postmenopausal Japanese women who had a late menopause and more reproductive years were at decreased risk for low bone mineral density, and may therefore be less prone to osteoporosis.     

Importance of shared genes and shared environments for symptoms of depression in older adults.

The Center for Epidemiologic Studies-Depression scale was administered to 68 identical and 161 fraternal twin pairs reared apart and 114 identical and 138 fraternal pairs reared together to ascertain relative genetic and environmental contributions to individual differences in self-reported depressive symptoms. Intraclass correlations and model fitting indicated that genetic influences explained 16% of the variance in the total depression scores and 19% for the Psychomotor Retardation and Somatic Complaints subscale, but heritability was minimal for the Depressed Mood and Well-Being subscales. Influence of family rearing context played a substantial role in explaining twin similarity, whereas unique life experiences accounted for the greatest proportion of variance. Significant age group differences were observed, with heritability greater in twins of 60 years of age or older than in twins under 60, especially for Psychomotor Retardation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

International variability in ages at menarche, first livebirth, and menopause. World Health Organization Collaborative Study of Neoplasia and Steroid Contraceptives

The occurrences and timing of reproduction-related events, such as menarche, first birth, and menopause, play major roles in a woman's life. There is a lack of comparative information on the overall patterns of the ages at and the timing between these events among different populations of the world. This study describes the variability in reproductive factors across populations in Europe, the Americas, Asia, Australia, and Africa. The study sample consisted of 18,997 women from 13 centers in 11 countries interviewed between 1979 and 1988 who comprised the control group in a World Health Organization international, multicenter case-control study of female cancers. All were surveyed with the same questionnaire and methodology. Overall, a typical woman in this study reached menarche at age 14 years and delivered her first live child 8 years later, at age 22. She was 50 years old at natural menopause and had had 36 years of reproductive life. The median ages at menarche varied across centers from 13 to 16 years. For all centers, the median age at first livebirth was 20 or more years, with the largest observed median (25 years) occurring in China. The median delay from menarche to first livebirth ranged from 5 to 11 years. Among the centers, the median age at natural menopause ranged between 49 and 52 years. In most populations, younger women had a first birth at a later age than did older women. This tendency was more accentuated in some populations. These results reveal, perhaps for the first time, the variability of reproductive histories across different populations in a large variety of geographic and cultural settings. Except for menopause, international variability is substantial for both biologically related variables (age at menarche) and culturally related variables (age at first birth). There is a generational effect, characterized by more variability of age at first birth and delay to first birth in the younger than in the older generations.     

Heritability of facet-level traits in a cross-cultural twin sample: support for a hierarchical model of personality

The common variance among personality traits can be summarized in the factors of the five-factor model, which are known to be heritable. This study examined heritability of the residual specific variance in facet-level traits from the Revised NEO Personality Inventory. Analyses of raw and residual facet scales across Canadian (183 monozygotic [MZ] and 175 dizogotic [DZ] pairs) and German (435 MZ and 205 DZ pairs) twin samples showed genetic and environmental influences of the same type and magnitude across the 2 samples for most facets. Additive genetic effects accounted for 25% to 65% of the reliable specific variance. Results provide strong support for hierarchical models of personality that posit a large number of narrow traits in addition to a few broader trait factors or domains. Facet-level traits are not simply exemplars of the broad factors they define; they are discrete constructs with their own heritable and thus biological basis.     

Genetic and environmental contributions to depression symptomatology: Evidence from Danish twins 75 years of age and older.

The heritability symptoms of depression were investigated in a sample of 406 same-sex Danish twin pairs 75 years of age and older. Twins completed an interview assessment that included symptoms of depression, which were scored on the following 3 scales: Somatic, Affect, and Total. Heritability estimates (h–2) for the Total (h–2?=?.34), Somatic (h–2?=?.31), and Affect (h–2?=?.27) scales were all moderate and statistically significant. For not one of the scales did h–2 vary significantly over the age range sampled, and although the observed twin correlations were substantially smaller among men as compared with women, none of the sex differences in heritability were statistically significant. Multivariate analyses indicated that all of the heritable effects on the Affect and Somatic subscales could be attributed to a single genetic factor. Depression symptoms in older adults may thus be more heritable than indicated in previous studies, although nonshared environmental factors clearly account for a majority of the variance. The implications of these findings for understanding the nature of late-life depression symptomatology are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A prospective study of reproductive factors and risk of epithelial ovarian cancer

BACKGROUND: Parity and long term use of oral contraceptives have been associated consistently with a decreased risk of ovarian cancer. However, previous reports of the relationship of other reproductive factors (time since first use or last use of oral contraceptives, age at menarche or menopause, age at first birth) with ovarian cancer have been inconsistent. METHODS: The authors studied these relationships in the Nurses' Health Study, a prospective cohort study of 121,700 female registered nurses aged 30-55 years in 1976 when the study began. From 1976 to 1988, 260 cases of confirmed epithelial ovarian cancer occurred among 1.2 million person-years of follow-up. RESULTS: A statistically significant inverse association was observed between parity and ovarian cancer risk (relative risk [RR] = 0.84; 95% confidence interval [CI] = 0.77-0.91 per pregnancy); age at first birth was not associated independently with risk. In age-adjusted analyses, a significant inverse association was noted between long term use of oral contraceptives and ovarian cancer, which was no longer significant after controlling for other ovarian cancer risk factors (RR with > or = 5 years' use: 0.65; 95% CI = 0.40-1.05). After control for duration of use, a weak nonsignificant inverse association was observed with time since first oral contraceptive use and no independent effect of time since last use. Neither age at menarche nor age at menopause was associated significantly with ovarian cancer risk. CONCLUSIONS: In this large prospective study, parity was the only reproductive factor that had a substantial independent association with ovarian cancer. Long term oral contraceptive use also appeared to have an inverse relationship with ovarian cancer, although this association was of borderline significance (P = 0.11) after adjustment for other risk factors.     

Age and the self-perception of ability: A twin study analysis.

2,974 adults, including 678 monozygotic and 547 dizygotic twin pairs (aged 27–86 yrs), self-rated ability on 6 factors: Interpersonal Competence, Workplace Skills, Trade Skills, Intellectual and Cultural, Domestic Skills, and Athletic Competition. Age accounted for no more than 2% of the variance on any factor, and, although there were significant gender effects, no significant Age?×?Gender interactions were observed. Twin similarity did not vary significantly with age, and biometrical variance component estimates were statistically homogeneous across age, with talent factor variance being apportioned approximately equally to genetic and nonshared environmental factors. Consistent failure to find age effects as well as consistent observation of significant heritability support the conclusion that self-concept crystallizes early in adulthood and reflects genetically influenced psychological characteristics. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Pubertal timing and substance use: Associations between and within families across late adolescence.

In the present study, between-family analyses of data from adolescent twin girls offer new evidence that early menarche is associated with earlier initiation and greater frequency of smoking and drinking. The role of personality factors and peer relationships in that association was investigated, and little support was found for their involvement. Novel within-family analyses replicating associations of substance use with pubertal timing in contrasts of twin sisters selected for extreme discordance for age at menarche are reported. Within-family replications demonstrated that the association of pubertal timing with substance use cannot be explained solely by between-family confounds. Within-family analyses demonstrated contextual modulation of the influence of pubertal timing: Its impact on drinking frequency is apparent only among girls in urban settings. Sibling comparisons illustrate a promising analytic tool for studying diverse developmental outcomes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Minimal genetic influences on plasma fibrinogen level in adult males in the NHLBI twin study

Plasma fibrinogen was determined in 189 twins participating at the Indiana center during the third examination of the NHLBI twin study with a mean age of 63 years. Moderate heritability estimates were obtained from 44 complete MZ pairs and 39 complete DZ pairs. After adjustment of fibrinogen levels for age and other confounding variables related to cardiovascular disease risk, the maximum likelihood heritability estimate was only 30% (p = 0.03). Plasma fibrinogen was most strongly associated with smoking and the presence of diabetes. Omitting all subjects with diabetes or cardiovascular disease further reduced the heritability estimates slightly, and most path models including genetic parameters provided no significant improvement in fit over a model determined solely by random environmental effects. Our results are consistent with the environment rather than genetic influences having a greater influence on the level of plasma fibrinogen.     

Genetic and environmental influences on EEG coherence

EEG coherence measures the covariation in electrical brain activity between two locations on the scalp and is used to study connectivity between cortical regions. The aim of this study was to determine the heritability of EEG coherence. Coherence was measured in a group of 213 16-yr-old twin pairs. By including male and female twin pairs in the sample, sex differences in genetic architecture were systematically examined. The EEG was obtained during quiet supine resting. Coherence was estimated for short and long distance combinations of electrode pairs along the anterior-posterior axis within a hemisphere for four frequency bands (delta, theta, alpha and beta). Averaged over all electrode combinations about 60% of the variance was explained by genetic factors for coherence in the theta, alpha and beta bands. For the delta band, the heritability was somewhat lower. No systematic sex differences in genetic architecture were found. All environmental influences were nonshared, i.e., unique factors including measurement error. Environmental factors shared by twin siblings did not influence variation in EEG coherence. These results suggest that individual differences in coherence form a potential candidate for (molecular) genetic studies on brain function.     

Sex and age effects on the inheritance of alcohol problems: A twin study.

Male monozygotic cotwins of probands with alcohol abuse-dependence (n?=?85) were more likely than male same-sex dizygotic cotwins (n?=?96) to report alcohol, drug, and conduct disorder problems. For women, rates of problem behavior did not differ between monozygotic (n?=?44) and same-sex dizygotic (n?=?43) cotwins. Opposite-sex dizygotic twin data (n?=?88) revealed significant cross-sex transmission; alcohol problems were greatest among male cotwins of female probands. For men, proportion of liability variance associated with additive genetic factors was significantly greater when proband had an early (h–2?=?.73?±?.18) rather than late (h–2?=?.30?±?.26) age of onset. For women, heritability did not vary as a function of proband's age of onset, and the pooled estimate suggested little genetic influence (h–2?=?.00, SE not computable). Findings suggest that genetic influences may be substantial only in the etiology of early-onset male alcoholism. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Quantitative genetics of serum sex hormone-binding globulin levels in participants in the San Antonio Family Heart Study

Sex hormone-binding globulin (SHBG) is a steroid-binding plasma protein with a high affinity for testosterone that has been inversely associated with cardiovascular disease risk in many populations. SHBG may also act as a receptor in some tissues. Although the function of SHBG is relatively well understood, comparatively little is known about genetic factors contributing to the normal variation of serum SHBG levels. We estimated the heritability (h2) of serum SHBG levels in 717 related Mexican-Americans participating in the San Antonio Family Heart Study (SAFHS). We found a significant heritability (h2 = 0.31, P < .0001) for serum SHBG levels; age, exogenous hormones, smoking status, diabetic status, and adiposity showed significant associations (P < .05) with mean levels of SHBG. Sex was associated with mean SHBG levels but not with genetic or environmental variance in SHBG levels; heritability estimates were the same for males and females. These results indicate a significant genetic influence on SHBG in Mexican-Americans. Thus, SHBG may prove to be an important indicator of genetic risk for cardiovascular disease in this population, as well as others.     

The heritability of cognitive functioning in very old adults: Evidence from Danish twins aged 75 years and older.

Heritable influences on cognitive functioning were investigated in a sample of 403 pairs of like-sex Danish twins aged 75 years and older. Twins completed the Mini-Mental State Examination and 3 other cognitive tests. Genetic factors accounted for 26–54% of the variance on these measures, with the balance being due to environmental factors that create differences rather than similarities among reared-together relatives. Deleting twins with severe cognitive impairment had little effect on the results, indicating that the heritability of cognitive functioning was not due entirely to genes affecting dementia. Neither age nor gender moderated twin similarity, and differential social contact could not account for correlation differences between monozygotic and dizygotic twins. These results replicate G. E. McClearn et al.'s (1997) study in indicating substantial genetic influences on late-life cognitive functioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Twin imitation for antisocial behavior: Implications for genetic and family environment research.

When twin pairs influence each other's behavior, observed variance is greater for monozygotic (MZ) twins than for dizygotic (DZ) twins under at least 1 of 2 conditions: (1) The trait has some heritability, and (2) MZ twins influence each other more than do DZ twins. Applied to a trait that has an underlying continuous distribution but is measured as a dichotomy, the presence of reciprocal twin influence predicts that if the base rate for the trait is not exactly 50%, then the prevalence of the trait should differ in MZ and DZ twin pairs. This prediction held for registered criminality in a large twin cohort. Methods of analysis that permit reciprocal twin interaction not only provide better statistical fits to the data but also yield estimates of heritability that agree with adoption data. Results suggest that the genetic influence on registered criminality may be more modest than previously thought. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Genetic architecture of learning and delayed recall: A twin study of episodic memory.

Objective: Although episodic memory is often conceptualized as consisting of multiple component processes, there is a lack of understanding as to whether these processes are influenced by the same or different genetic determinants. The aim of the present study was to utilize multivariate twin analyses to elucidate the degree to which learning and delayed recall, two critical measures of episodic memory performance, have common or different genetic and environmental influences. Method: Participants from the Vietnam Era Twin Study of Aging (314 monozygotic twin pairs, 259 dizygotic twin pairs, and 47 unpaired twins) were assessed using the second edition of the California Verbal Learning Test. Mean age at the time of the evaluation was 55.4 years (SD = 2.5). Results: Model fitting revealed the presence of a higher-order latent factor influencing learning, short- and long-delay free recall, with a heritability of .36. The best-fitting model also indicated specific genetic influences on learning, which accounted for 10% of the overall variance. Given that learning involves the acquisition and retrieval of information, whereas delayed recall involves only retrieval, we conclude that these specific effects are likely to reflect genes that are specific to acquisition processes. Conclusion: These results demonstrate that even in nonclinical populations, it is possible to differentiate component processes in episodic memory. These different genetic influences may have implications for gene association studies, as well as other genetic studies of cognitive aging and disorders of episodic memory such as Alzheimer's disease or mild cognitive impairment. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Heritability of anxiety sensitivity: a twin study

OBJECTIVE: In attempting to explain the familial predisposition to panic disorder, most studies have focused on the heritability of physiologic characteristics (e.g., CO2 sensitivity). A heretofore unexplored possibility is that a psychological characteristic that predisposes to panic-anxiety sensitivity-might be inherited. In this study, the authors examined the heritability of anxiety sensitivity through use of a twin group. METHOD: Scores on the Anxiety Sensitivity Index were examined in a group of 179 monozygotic and 158 dizygotic twin pairs. Biometrical model fitting was conducted through use of standard statistical methods. RESULTS: Broad heritability estimate of the Anxiety Sensitivity Index as a unifactorial construct was 45%. Additive genetic effects and unique environmental effects emerged as the primary influences on anxiety sensitivity. There was no evidence of genetic discontinuity between normal and extreme scores on the Anxiety Sensitivity Index. CONCLUSIONS: This study suggests that one psychological risk factor for the development of panic disorder-anxiety sensitivity-may have a heritable component. As such, anxiety sensitivity should be considered in future research on the heritability of panic disorder.     

Posttraumatic stress disorder and the genetic structure of comorbidity.

This study used structural equation modeling to examine the genetic and environmental architecture of latent dimensions of internalizing and externalizing psychiatric comorbidity and explored structural associations between posttraumatic stress disorder (PTSD) and these dimensions. Data were drawn from the Vietnam Era Twin Registry and included lifetime diagnoses for PTSD and a range of other psychiatric disorders for 3,372 male–male twin pairs. Examination of the phenotypic structure of these disorders revealed that PTSD cross-loaded on both Internalizing and Externalizing common factors. Biometric analyses suggested largely distinct genetic risk factors for the latent internalizing and externalizing comorbidity dimensions, with the total heritability of the Externalizing factor (69%) estimated to be significantly stronger than that for Internalizing (41%). Nonshared environment explained the majority of the remaining variance in the Internalizing (58%) and Externalizing (20%) factors. Shared genetic variance across the 2 dimensions explained 67% of their phenotypic correlation (r = .52). These findings have implications for conceptualizations of the etiology of PTSD and its location in an empirically based nosology. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A breast cancer case-control study in Girona, Spain. Endocrine, familial and lifestyle factors

This study was designed to explore risk factors for breast cancer with emphasis on the detection of clinical markers of the hormonal imbalance during the perimenarche. Three hundred and thirty women diagnosed with breast cancer and 346 population controls were identified and interviewed in Girona, Spain between 1986 and 89. Cases were more likely than controls to have had long menstrual periods in the first 5 years after menarche [odds ratio (OR) = 3.0], to experience menopause at a late age (OR = 1.5) and to report acne during adolescence (OR = 1.6). Family history of breast cancer was associated with an increased risk (OR = 2.3). Cases reported a lower use of drug treatments for anxiety and sleep disorders than controls. Moderate alcohol drinkers and smokers were at lower risk for breast cancer. No statistically significant association with breast cancer was observed for number of children, age at last pregnancy, oral contraceptive use, hormonal treatment after menopause and weight perception during the teenage years. Hormonal changes in the years following menarche may be relevant to breast cancer risk. The roles of menstrual period length and acne during adolescence should be further explored.     

Reproductive and menstrual factors in relation to mammographic parenchymal patterns among perimenopausal women

The relationship between mammographic patterns and reproductive and menstrual factors was examined in 3640 Norwegian women, aged 40-56 years, participating in the Third Troms? study conducted in 1986-87. Epidemiological data were obtained from questionnaires. The mammograms were categorised into five groups. This categorisation is based on anatomic-mammographic correlations, following three-dimensional (thick slice technique) histopathologic-mammographic comparisons, rather than simple pattern reading. Patterns 1-3 were combined into a low-risk group and patterns 4 and 5 into a high-risk group for analysis. Women who had more than four children were 90% less likely to have a high-risk pattern than nulliparous women (OR = 0.09, 95% CI 0.04-0.16) controlling for age, weight, height and menopausal status. Furthermore, those who first gave birth over 34 years of age were more than twice as likely to have a high-risk pattern than those giving birth in their teens (OR = 2.37, 95% CI 1.23-4.56) adjusting for parity. Among post-menopausal women, age at menarche was negatively (P for trend = 0.015) and late age at menopause positively (P for trend = 0.072) related to high-risk patterns. Among premenopausal women, age at menarche was positively related to high-risk patterns (P for trend = 0.001). Also, menopausal status rather than age was associated with high-risk patterns. These findings support the opinion that reproductive and menstrual factors are involved in determining the mammographic parenchymal pattern among perimenopausal women.     

A population-based twin study of self-esteem and gender

BACKGROUND: Self-esteem (SE), a widely used construct in the social sciences, is usually conceptualized as a reflection of socialization and interpersonal experiences that may differ considerably between the genders. METHODS: The Rosenberg self-esteem scale was assessed at personal interview in both members of 3793 unselected twin pairs (1517 male-male, 856 female-female and 1420 male-female) from the population-based Virginia Twin Registry. Gender effects on SE were assessed by both analysis of variance and biometrical twin modelling. RESULTS: The mean SE score was slightly but significantly lower in women v. men, and in women who grew up with a male v. a female co-twin. Twin modelling suggested that: (i) individual differences in self-esteem in both men and women were best explained by genetic and individual-specific environment factors; (ii) heritability estimates were similar in women (32%) and in men (29%); and (iii) the same genetic factors that influenced SE in women also influenced SE in men. Analyses supported the validity of the equal environment assumption for SE. The heritability of SE cannot be explained by the moderate correlation between SE and symptoms of depression. CONCLUSIONS: These results are inconsistent with prominent gender-related aetiological models for SE, which postulate that individual differences arise from socialization experiences both within and outside the home of origin which differ widely for the two genders. Instead, a significant proportion of the population variance in SE is due to genetically-influenced temperamental variables that are the same in men and women.