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Nancy L Pedersen

Publications and source records attributed to Nancy L Pedersen.

At least 91 records · Page 5Linked to original sources
PubMed2003

Remembered parental bonding in adult twins: genetic and environmental influences.

One common assumption in psychology is the impact of parenting and parent-child relationships on the child's adjustment throughout the life span. Studies have indicated that there are genetic influences on memories of parenting, but how these influences are mediated has not typically been investigated. A sample of 150 pairs of monozygotic and 176 pairs of dizygotic Swedish twin women reported on personal characteristics and on remembered relationships with their mother and father using the Parental Bonding Instrument (PBI). Quantitative genetic analyses showed moderate genetic influences for remembered parental warmth, which also was partly explained by genetic influences for optimism, aggression, and humor. The other two PBI scales, authoritarianism and protectiveness, showed only shared and nonshared environmental influences. One interpretation of the findings is that heritable personal characteristics of children elicit parental warmth. However, other explanations such as personality characteristics influencing how experiences with parents are interpreted or circumstances in adult life that affect the recall of experiences could not be ruled out.

Adult↗
PubMed2003

Latent growth curve analyses of accelerating decline in cognitive abilities in late adulthood.

Latent growth models were applied to data from the Swedish Adoption/Twin Study of Aging to discover if the rate of change in cognitive performance increased from middle age to later adulthood. The sample included 590 participants aged 44 to 88 years at first measurement. Data were gathered at 2 follow-up occasions at intervals of 3 years. Cognitive ability was assessed through 11 tests that tapped crystallized, fluid, memory, and spatial abilities and perceptual speed. Results indicated stability for measures of crystallized ability, linear age changes for many cognitive abilities, and a significant acceleration in linear decline after age 65 for measures with a large speed component. Gender differences were found only in mean level, not in rate of decline.

Adoption↗
PubMed2003

Evidence for a QTL on chromosome 19 influencing LDL cholesterol levels in the general population.

The genetic basis of cardiovascular disease (CVD) with its complex etiology is still largely elusive. Plasma levels of lipids and apolipoproteins are among the major quantitative risk factors for CVD and are well-established intermediate traits that may be more accessible to genetic dissection than clinical CVD end points. Chromosome 19 harbors multiple genes that have been suggested to play a role in lipid metabolism and previous studies indicated the presence of a quantitative trait locus (QTL) for cholesterol levels in genetic isolates. To establish the relevance of genetic variation at chromosome 19 for plasma levels of lipids and apolipoproteins in the general, out-bred Caucasian population, we performed a linkage study in four independent samples, including adolescent Dutch twins and adult Dutch, Swedish and Australian twins totaling 493 dizygotic twin pairs. The average spacing of short-tandem-repeat markers was 6-8 cM. In the three adult twin samples, we found consistent evidence for linkage of chromosome 19 with LDL cholesterol levels (maximum LOD scores of 4.5, 1.7 and 2.1 in the Dutch, Swedish and Australian sample, respectively); no indication for linkage was observed in the adolescent Dutch twin sample. The QTL effects in the three adult samples were not significantly different and a simultaneous analysis of the samples increased the maximum LOD score to 5.7 at 60 cM pter. Bivariate analyses indicated that the putative LDL-C QTL also contributed to the variance in ApoB levels, consistent with the high genetic correlation between these phenotypes. Our study provides strong evidence for the presence of a QTL on chromosome 19 with a major effect on LDL-C plasma levels in outbred Caucasian populations.

Adolescent↗
PubMed2003

Shared rearing environment in migraine: results from twins reared apart and twins reared together.

BACKGROUND: Studies of twins who are separated from each other early in life and are reared in different environments offer the opportunity to resolve variation in liability to disease. OBJECTIVE: To evaluate the importance of genetic and environmental influences in migraine; in particular, addressing the role of the shared rearing environment. METHODS: A population-based cohort of twins, including a subsample of 314 pairs reared apart and 364 matched control pairs reared together, was drawn from the Swedish Twin Registry. Data on lifetime migraine was collected via self-administered questionnaires mailed to twins aged 42 to 81 years. Quantitative genetic models and regression models were used to analyze sources of twin similarity. RESULTS: We found nonsignificant shared rearing environmental influences on migraine for men (17%) and no rearing effects at all for women. The heritability of migraine was estimated at 38% (95% confidence interval, 0 to 73) for men and 48% (95% confidence interval, 27 to 65) for women. Among monozygotic twins reared apart, those separated at 3 years of age or earlier were more similar for lifetime migraine than those separated later, and this was especially true for women. CONCLUSION: In agreement with previous twin data, family resistance in migraine is mainly due to genetic factors, whereas environmental influences make family members different, not similar.

Adult↗
PubMed2003

Does participation in leisure activities lead to reduced risk of Alzheimer's disease? A prospective study of Swedish twins.

This study examined whether participation in leisure activities during early and middle adulthood was associated with reduced risk of Alzheimer's disease. The sample consisted of 107 same-sex twin pairs discordant for dementia and for whom information on leisure activities was self-reported more than 20 years prior to clinical evaluation. A factor analysis of these activities yielded three activity factors: intellectual-cultural, self-improvement, and domestic activity. Matched-pair analyses compared activities within the discordant twin pairs while controlling for level of education. For the total sample, participation in a greater overall number of leisure activities was associated with lower risk of both Alzheimer's disease and dementia in general. Greater participation in intellectual-cultural activities was associated with lower risk of Alzheimer's disease for women, although not for men.

Aged↗
PubMed2003

Depressive symptoms and aging: the effects of illness and non-health-related events.

This study examined whether depressive symptoms increase with age longitudinally, and it evaluated two potential sources of influence-declining health and non-health-related negative life events. Adults aged 29-93 years from the Swedish Adoption/Twin Study of Aging completed the Center for Epidemiologic Studies-Depression scale three times at 3-year intervals. Analyses were performed on one twin (n = 877) and repeated on the second twin (n = 909) as a nonindependent replication. Depressive symptoms increased modestly with age in both men and women, particularly in the older participants. Health status was correlated with depressive symptoms, but new illnesses in the previous 3 years did not consistently predict increases in depressive symptoms longitudinally. Negative life events in the previous 3 years predicted depressive symptoms. Notably, depressive symptoms also predicted future negative life events.

Adult↗
PubMed2003

Occupational magnetic field exposure and neurodegenerative disease.

BACKGROUND: Several studies have identified occupational exposure to extremely low-frequency electromagnetic fields (EMF) as a potential risk factor for neurodegenerative disease, but the evidence is contradictory and inconclusive. METHODS: We conducted a cohort study to explore these associations. We studied all economically active individuals in the Swedish 1980 census (4,812,646 subjects), and followed them for neurodegenerative disease mortality from 1981 through 1995. Information about occupation was available for 1970 and 1980. A job-exposure matrix based on magnetic field measurements was used to assess EMF exposure. RESULTS: An increased risk of Alzheimer's disease mortality was observed among men exposed both in 1970 and 1980 (relative risk = 2.3; 95% confidence interval = 1.6-3.3 for exposure >/=0.5 microT). The associations were most pronounced for early-onset Alzheimer's disease mortality or with follow-up limited to 10 years after the last known occupation. Amyotrophic lateral sclerosis was not associated with EMF exposure, but the risk estimate with "electrical and electronics work" was 1.4 (95% confidence interval = 1.1-1.9). CONCLUSIONS: Our study gives some support to the hypothesis that EMF exposure increases the risk of early-onset Alzheimer's disease, and suggests that magnetic field exposure may represent a late-acting influence in the disease process. Electric shock is an unlikely explanation for the increased risk of amyotrophic lateral sclerosis in "electrical and electronics work" in this study.

Adolescent↗
PubMed2003

No linkage to obesity in candidate regions of chromosome 2 and 10 in a selected sample of Swedish twins.

The aim of the current study was to investigate the importance of genetic and environmental effects in the variation of body mass index, and to investigate linkage for obesity to previously reported candidate regions on chromosome 2 and 10. A sample of 1422 twin pairs from the population based Swedish Twin Registry was used in order to estimate the genetic and environmental effects in the variation of body mass index by means of structural equation modeling. A selection of those, 51 concordant and 155 discordant for obesity, was used for the linkage analysis by implementing the "combined" Haseman-Elston approach. Heritability of body mass index ranged from 59-70%, implying that genetic effects were of importance for the variation of obesity, and there were significant sex and age differences. Linkage could not be verified in candidate regions of chromosomes 2 and 10, indicating that these genetic variants have a significant effect in extreme obese populations rather than in moderately obese Caucasians. However, the results were sensitive to issues related to power, minor effects of the genes, ethnic differences and the complex mechanism underlying obesity.

Adolescent↗
PubMed2003

Two-locus linkage analysis applied to putative quantitative trait loci for lipoprotein(a) levels.

Plasma levels of lipoprotein(a) - Lp(a) - are associated with cardiovascular risk (Danesh et al., 2000) and were long believed to be influenced by the LPA locus on chromosome 6q27 only. However, a recent report of Broeckel et al. (2002) suggested the presence of a second quantitative trait locus on chromosome 1 influencing Lp(a) levels. Using a two-locus model, we found no evidence for an additional Lp(a) locus on chromosome 1 in a linkage study among 483 dizygotic twin pairs.

Adolescent↗
PubMed2003

Importance of genetic effects for characteristics of the human iris.

The relative importance of genetic influences (heritability) on five general textural quality characteristics of the human iris was assessed using sex and age limitation models. Colour photographs of irises were available from 100 monozygotic twin pairs, 99 dizygotic twin pairs, and 99 unrelated randomly paired age-matched German subjects. Comparative scales were constructed and two judges who were blind to zygosity independently rated five characteristic of the subjects' left iris. Inter-rater reliabilities were larger than.90 for all five scales. The heritabilities for the five iris characteristics ranged from.51-.90. No sex-specific genetic factors were found for the iris characteristics. Age-group differences in heritability were found for one of the five iris characteristics - "distinction of white dot rings". Heritability was greater for the older cohort (90%) than the younger (73%). The iris characteristics that showed the next highest additive-genetic effect were "contractional furrows" (78%) and "frequency of crypts" in the main stroma leaf (66%).

Adolescent↗
PubMed2003

Data modeling and data communication in GenomEUtwin.

Database infrastructure has become a critical component for competitive life sciences research and discovery. The explosion of data requires that the data are properly loaded, accessed, managed, queried, analyzed, and shared with others. The key purpose of the population-based twin cohorts housed at different institutions in Europe is to gather an extremely large quantity of information from their twin populations, and share it. Longitudinal research over a long period of time, hopefully generations, demands completely new methods and systems to handle the gathering of information and storing. These cohorts bring to the fore problems concerning the need for a standardization of research data and a computer and storage strategy. In the following we describe the preliminary strategy being implemented in the Database Core of GenomEUtwin.

Database Management Systems↗
PubMed2003

Heritability of adult body height: a comparative study of twin cohorts in eight countries.

A major component of variation in body height is due to genetic differences, but environmental factors have a substantial contributory effect. In this study we aimed to analyse whether the genetic architecture of body height varies between affluent western societies. We analysed twin data from eight countries comprising 30,111 complete twin pairs by using the univariate genetic model of the Mx statistical package. Body height and zygosity were self-reported in seven populations and measured directly in one population. We found that there was substantial variation in mean body height between countries; body height was least in Italy (177 cm in men and 163 cm in women) and greatest in the Netherlands (184 cm and 171 cm, respectively). In men there was no corresponding variation in heritability of body height, heritability estimates ranging from 0.87 to 0.93 in populations under an additive genes/unique environment (AE) model. Among women the heritability estimates were generally lower than among men with greater variation between countries, ranging from 0.68 to 0.84 when an additive genes/shared environment/unique environment (ACE) model was used. In four populations where an AE model fit equally well or better, heritability ranged from 0.89 to 0.93. This difference between the sexes was mainly due to the effect of the shared environmental component of variance, which appears to be more important among women than among men in our study populations. Our results indicate that, in general, there are only minor differences in the genetic architecture of height between affluent Caucasian populations, especially among men.

Adult↗
PubMed2003

The genetics of coronary heart disease: the contribution of twin studies.

Despite the decline in coronary heart disease in many European countries, the disease remains an enormous public health problem. Although we know a great deal about environmental risk factors for coronary heart disease, a heritable component was recognized a long time ago. The earliest and best known examples of how our genetic constitution may determine cardiovascular risk relate to lipoprotein(a), familial hypercholesterolaemia and apolipoprotein E. In the past 20 years a fair number of polymorphisms assessed singly have shown strong associations with the disease but most are subject to poor repeatability. Twins constitute a compelling natural experiment to establish the genetic contribution to coronary heart disease and its risk factors. GenomEUtwin, a recently funded Framework 5 Programme of the European Community, affords the opportunity of comparing the heritability of risk factors in different European Twin Registries. As an illustration we present the heritabilities of systolic and diastolic blood pressure, based on data from over 4000 twin pairs from six different European countries and Australia. Heritabilities for systolic blood pressure are between 52 and 66% and for diastolic blood pressure between 44 and 66%. There is no evidence of sex differences in heritability estimates and very little to no evidence for a significant contribution of shared family environment. A non-twin based prospective case/cohort study of coronary heart disease and stroke (MORGAM) will allow hypotheses relating to cardiovascular disease, generated in the twin cohorts, to be tested prospectively in adult populations. Twin studies have also contributed to our understanding of the life course hypothesis, and GenomEUtwin has the potential to add to this.

Australia↗
PubMed2003

Stroke research in GenomEUtwin.

Stroke is one of the leading causes of severe disability and death in the world. In the present article we outline possibilities and limitations for future stroke research within the GenomEUtwin. The combined sample of twins born before 1958 from Denmark, Finland, and Sweden, and available for follow-up into the second millennium for non-fatal and fatal stroke events through national inpatient and death registers exceeds 70,000 twin pairs. This sample size will enable the study of genetic influences on stroke and major stroke subtypes. Large samples of twins in GenomEUtwin have been followed up repeatedly through interviews and questionnaires concerning a variety of exposures and potential risk factors for stroke. We briefly outline how this information can be combined with the health register information for epidemiologic and genetic epidemiologic studies of stroke. We also present the number of twin pairs concordant and discordant for stroke in Denmark, Finland and Sweden, and time lags between events for twins concordant for stroke. This information illustrates that the number of affected sib pairs for linkage studies is relatively limited, but the sample sizes are promising for association studies.

Denmark↗
PubMed2003

Longevity studies in GenomEUtwin.

Previous twin studies have indicated that approximately 25% of the variation in life span can be attributed to genetic factors and recent studies have also suggested a moderate clustering of extreme longevity within families. Here we discuss various definitions of extreme longevity and some analytical approaches with special attention to the challenges due to censored data. Lexis diagrams are provided for the Danish, Dutch, Finnish, Italian, Norwegian, and Swedish Twin registries hereby outlining possibilities for longevity studies within GenomEUtwin. We extend previous analyses of lifespan for the Danish 1870-1900 twin cohorts to include the new 1901-1910 cohorts, which are consistent with the previous findings. The size of the twin cohorts in GenomEUtwin and the existence of population-based, nationwide health and death registers make epidemiological studies of longevity very powerful. The combined GenomEUtwin sample will also allow detailed age-specific heritability analyses of lifespan. Finally, it will provide a resource for identifying unusual sibships (i.e., dizygotic twin pairs) where both survived to extreme ages, as a basis for discovering genetic variants of importance for extreme survival.

Adult↗
PubMed2002

Diabetes mellitus is a risk factor for vascular dementia, but not for Alzheimer's disease: a population-based study of the oldest old.

BACKGROUND: The purpose of this study was to examine if Type 2 diabetes mellitus is a risk factor for dementia in very old age, specifically for Alzheimer's disease (AD) and vascular dementia (VaD). METHODS: We evaluated the risk of dementia in relation to Type 2 diabetes using a population-based sample of 702 individuals aged 80 years and older (mean age 83 years). A total of 187 persons received a dementia diagnosis. Thirty-one individuals had a diabetes diagnosis prior to onset of the dementia. RESULTS: Cox proportional hazard analyses, adjusted for age, gender, education, smoking habits, and circulatory diseases, indicated an elevated risk to develop VaD (relative risk = 2.54, 95% confidence interval 1.354.78) in individuals with diabetes mellitus. No association was found between diabetes and AD. CONCLUSION: Type 2 diabetes is selectively related to the different subtypes of dementia. There is no increased risk of AD but more than a twofold risk of VaD in persons with diabetes.

Aged↗
PubMed2002

Telephone screening to identify potential dementia cases in a population-based sample of older adults.

This study examined the utility of the TELE, a telephone assessment for dementia, in a sample of 269 individuals that was not selected on the basis of previous dementia diagnosis. Thus, the conditions of the study reflect the actual situation in which a screening instrument might be employed. Scores on TELE were compared to dementia diagnoses. Using the best cutoff score, sensitivity was .86 and specificity was .90. Longitudinal follow-up established that false positives primarily included those who subsequently developed dementia. Telephone screening for dementia has both clinical and research applications. One recommendation based on our experience is that longitudinal studies should include a telephone interview component for anyone who drops out of the study, to enable characterizing the cognitive status of dropouts.

Aged↗