Biomedical subjects

Nancy L Pedersen

Publications and source records attributed to Nancy L Pedersen.

104 records · Page 6Linked to original sources

PubMed2002

Gastroesophageal reflux disease in monozygotic and dizygotic twins.

BACKGROUND & AIMS: Gastroesophageal reflux disease (GERD) interferes with the quality of life and carries an increased risk for esophageal adenocarcinoma. We investigated genetic influence in the development of reflux. METHODS: We compared concordance for reflux in monozygotic (MZ) and dizygotic (DZ) twins. All twins age 55 and older in the nationwide Swedish Twin Registry were invited to participate. Data were collected by computer-assisted telephone interviews. Reflux disease was defined by symptomatic heartburn or acid regurgitation occurring at least weekly. RESULTS: A total of 2178 monozygotic, 3219 same-sex dizygotic, and 3014 unlike-sex dizygotic twin pairs provided information. Overall, 15.3% of the twins had reflux. In men, the intraclass correlation for reflux was 0.29 (95% confidence interval [CI], 0.15-0.43) for monozygotic and 0.13 (95% CI, 0.02-0.25) for dizygotic pairs. In women, the correlation was 0.33 (95% CI, 0.22-0.44) for monozygotic and 0.14 (95% CI, 0.04-0.24) for dizygotic pairs. For unlike-sex dizygotic pairs, the correlation was 0.06 (95% CI, -0.01 to 0.14). Concordance for reflux was not caused by inherited obesity or alcohol use; inherited smoking may be a minor factor. CONCLUSIONS: The increased concordance for reflux in monozygotic pairs, compared with dizygotic pairs, indicates genetic rather than shared environmental effects. Heritability accounted for 31% (23%-39%) of the liability to reflux disease in this population.

Aged↗

PubMed2002

Anxiety, cognitive performance, and cognitive decline in normal aging.

A sample of 704 cognitively intact individuals (M age = 63.7 years) performed a battery of cognitive tests on as many as three occasions, at approximately 3-year intervals. The authors used random effects models to analyze cross-sectional relationships between cognitive performance and state anxiety and longitudinal relationships between cognitive change and neuroticism, after controlling for gender, age, and education. Cross-sectionally, higher state anxiety was associated with poorer performance on Wechsler Adult Intelligence Scale Synonyms, WIT III Analogies, Koh's Block Design, two measures of visual learning (Names and Faces and Thurstone's Picture Memory), and, for men, CVB-Scales Digit Span Test and Card Rotations. In longitudinal models, the main effects for neuroticism were significant for Block Design, Symbol Digit, and Names and Faces, but there were no significant interactions among neuroticism, gender, and time. These results provide some support for Eysenck's processing efficiency theory but none for neuroticism as a risk factor for cognitive decline in normal aging.

Aged↗

PubMed2002

Terminal decline and markers of cerebro- and cardiovascular disease: findings from a longitudinal study of the oldest old.

The purpose of this study was to examine the cognition-survival relationship among nondemented individuals in late life. The longitudinal design included three examinations at 2-year intervals. At baseline, 466 individuals (age range = 80-98) were examined. During the 6 years of follow-up, 206 individuals died. Four survival groups were defined on the basis of mortality prior to the subsequent measurement occasion. Tests of cognitive functioning encompassed the domains of crystallized knowledge, inductive reasoning, visuospatial ability, short-term memory, episodic memory, and speed. Significant associations were found between cognitive performance at baseline and subsequent survival. After adjusting for stroke and markers of cardiovascular disease, the authors found that only three out of six cognitive domains remained significant predictors of survival. The longitudinal analyses revealed limited evidence for an accelerated decline prior to death. The main results suggest that level of cognitive performance in late life is associated with proximity to death, that this relationship is longstanding, and that it is partially influenced by compromised cardio- and cerebrovascular functioning.

Aged↗

PubMed2002

Gender and health: a study of older unlike-sex twins.

OBJECTIVES: The primary goal of this study was to assess gender differences in various measures of health conditions, symptoms, and self-rated health among older persons by comparing brothers and sisters in a sample of unlike-sex twins. METHODS: All living pairs of unlike-sex twins born between 1906 and 1925 were identified through the Swedish Twin Registry and sent surveys assessing health and other factors. This population-based sample consisted of 605 twin pairs. Paired sample t tests were used to analyze gender differences in health-related measures, including a three-level measure of health problems based on physicians' ratings. RESULTS: Women had more total health conditions, not life-threatening health conditions, somewhat life-threatening cardiovascular conditions, and physical and psychological symptoms. Men had more very life-threatening health conditions and cardiovascular conditions. No gender differences were found in somewhat life-threatening health conditions, total cardiovascular conditions, or self-rated health. DISCUSSION: Important gender differences and similarities in health were found using an unlike-sex twin design that reduced variability due to background characteristics. This design also minimized problems caused by gender differences in survival. Research on gender and health in older persons requires more detailed approaches to address the complexity of this topic.

Aged↗

PubMed2002

Repeated blood pressure measurements in a sample of Swedish twins: heritabilities and associations with polymorphisms in the renin-angiotensin-aldosterone system.

BACKGROUND: Twin and family studies have shown that genetic effects explain a relatively high amount of the phenotypic variation in blood pressure. However, many studies have not been able to replicate findings of association between specific polymorphisms and diastolic and systolic blood pressure. METHODS: In a structural equation-modelling framework the authors investigated longitudinal changes in repeated measures of blood pressures in a sample of 298 like-sexed twin pairs from the population-based Swedish Twin Registry. Also examined was the association between blood pressure and polymorphisms in the angiotensin-I converting enzyme and the angiotensin II receptor type 1 with the 'Fulker' test. Both linkage and association were tested simultaneously revealing whether the polymorphism is a Quantitative Trait Locus (QTL) or in linkage disequilibrium with the QTL. RESULTS: Genetic influences explained up to 46% of the phenotypic variance in diastolic and 63% of the phenotypic variance in systolic blood pressure. Genetic influences were stable over time and contributed up to 78% of the phenotypic correlation in both diastolic and systolic blood pressure. Non-shared environmental effects were characterised by time specific influences and little transmission from one time point to the next. There was no significant linkage and association between the polymorphisms and blood pressure. CONCLUSIONS: There is a considerable genetic stability in both diastolic and systolic blood pressure for a 6-year period of time in adult life. Non-shared environmental influences have a small long-term effect. Although associations with the polymorphisms could not be replicated, results should be interpreted with caution due to power considerations.

Aged↗

PubMed2002

Heritabilities of apolipoprotein and lipid levels in three countries.

This study investigated the influence of genes and environment on the variation of apolipoprotein and lipid levels, which are important intermediate phenotypes in the pathways toward cardiovascular disease. Heritability estimates are presented, including those for apolipoprotein E and AII levels which have rarely been reported before. We studied twin samples from the Netherlands (two cohorts; n = 160 pairs, aged 13-22 and n = 204 pairs, aged 34-62), Australia (n = 1362 pairs, aged 28-92) and Sweden (n = 302 pairs, aged 42-88). The variation of apolipoprotein and lipid levels depended largely on the influences of additive genetic factors in each twin sample. There was no significant evidence for the influence of common environment. No sex differences in heritability estimates for any phenotype in any of the samples were observed. Heritabilities ranged from 0.48-0.87, with most heritabilities exceeding 0.60. The heritability estimates in the Dutch samples were significantly higher than in the Australian sample. The heritabilities for the Swedish were intermediate to the Dutch and the Australian samples and not significantly different from the heritabilities in these other two samples. Although sample specific effects are present, we have shown that genes play a major role in determining the variance of apolipoprotein and lipid levels in four independent twin samples from three different countries.

Adolescent↗

PubMed2002

The Swedish Twin Registry in the third millennium.

Since the Swedish Twin Registry was first established in the late 1950s to study the importance of smoking and alcohol consumption on cancer and cardiovascular diseases, it has been expanded and updated on several occasions. The focus has similarly broadened to most common complex diseases. The content of the database is described, ongoing projects based on the registry are summarized, and we review some of the principal findings on aging, cancer and cardiovascular disease that have come from the registry. Ongoing efforts and future plans for the STR are discussed. Among others, we plan blood collection and genotyping to study the genetic bases of complex diseases, a first contact ever with the cohorts born after 1958, and in-depth studies of selected diseases, such as Parkinson's disease and chronic fatigue syndrome.

Alcohol Drinking↗

PubMed2002

Genetic and environmental influences on expression of recurrent headache as a function of the reporting age in twins.

To explore age-related mechanisms in the expression of recurrent headache, we evaluated whether genetic and environmental influences are a function of the reporting age using questionnaire information that was gathered in 1973 for 15- to 47-year-old Swedish twins (n = 12,606 twin pairs). Liability to mixed headache (mild migraine and tension-type headache) was explained by non-additive genetic influences (49%) in men aged from 15 to 30 years and additive genetic plus shared environmental influences (28%) in men aged from 31 to 47 years. In women, the explained proportion of variance, which was mainly due to additive genetic effects, ranged from 61% in adolescent twins to 12% in twins aged from 41 to 47 years, whereas individual specific environmental variance was significantly lower in twins aged from 15 to 20 years than in twins aged from 21 to 30 years. Liability to migrainous headache (more severe migraine) was explained by non-additive genetic influences in men, 32% in young men and 45% in old men, while total phenotypic variance was significantly lower in young men than in old men. In women, the explained proportion of variance ranged from 91% in the youngest age group to 37% in the oldest age group, with major contributions from non-additive effects in young and old women (15-20 years and 41-47 years, respectively) and additive genetic effects in intermediate age groups (21-40 years). While total variance showed a positive age trend, genetic variance tended to be stable across age groups, whereas individual specific environmental variance was significantly lower in adolescent women as compared to older women.

Adolescent↗

PubMed2002

Individual variation for cognitive decline: quantitative methods for describing patterns of change.

What are the best quantitative methods for studying cognitive decline? This question was investigated in a sample of 638 individuals aged 50 years and older from the Swedish Adoption/Twin Study of Aging. A battery of cognitive tests tapping multiple domains was administered to each individual from 2 to 7 times over a span of 10 years. Four methods of operationalizing cognitive decline were compared: change scores, a criterion-based method, least squares, and random effects regression (RER). The RER results were most consistent with a significant decline across measures and differences between demented and nondemented individuals. Predicted slopes from the RER model also showed the strongest interrelationships within and across cognitive domains as indicated by factor analysis results and stronger associations with demographic, health, and psychosocial predictors.

Adult↗

PubMedDate not supplied

Chronic widespread pain and its comorbidities: a population-based study.

BACKGROUND: Chronic widespread pain (CWP), the cardinal symptom of fibromyalgia, is prevalent and co-occurs with numerous symptom-based conditions such as chronic fatigue syndrome, joint pain, headache, irritable bowel syndrome, and psychiatric disorders. Few studies have examined the comorbidities of CWP in the general population. Furthermore, little is known about the importance of familial (genetic and family environmental) factors in the etiology of co-occurrence. METHODS: Data were obtained from 44 897 individuals in the Swedish Twin Registry via computer-assisted telephone interview from 1998 through 2002 (age >/=42 years; 73.2% response rate). Screening for CWP was based on the American College of Rheumatology criteria without clinical evaluation. Measures for comorbidities were based on standard criteria when available. Odds ratios (ORs) were calculated in case-control and co-twin control designs to assess the effect of familial confounding in the associations. RESULTS: Considerable co-occurrences were found in CWP cases for chronic fatigue (OR, 23.53; 95% confidence interval [CI], 19.67-28.16), joint pain (OR, 7.41; 95% CI, 6.70-8.21), depressive symptoms (OR, 5.26; 95% CI, 4.75-5.82), and irritable bowel syndrome (OR, 5.17; 95% CI, 4.55-5.88). In co-twin control analyses, ORs were no longer significant for psychiatric disorders, whereas they decreased but remained significant for most other comorbidities. No changes in ORs were observed for headache. CONCLUSIONS: Associations between CWP and most comorbidities are mediated by unmeasured genetic and family environmental factors in the general population. The extent of mediation via familial factors is likely to be disorder specific.

Adult↗

PubMedDate not supplied

Sources of influence on rate of cognitive change over time in Swedish twins: an application of latent growth models.

The use of latent growth models to examine influence on individual differences on ability level versus rate of change were examined for measures of fluid ability, memory, and perceptual speed in a sample of twins from the Swedish Adoption/Twin Study of Aging. Results indicated a larger amount of individual variation for average ability level (i.e., intercept) than rate of change (i.e., slope) for all three traits: Block Design, Thurstone's Picture Memory, and Symbol Digit. Generally, genetic influences were of greater importance to individual variation in ability level whereas variation for rate of change exhibited a larger environmental component. These findings support theories of increasing environmental influences with age. When genetic and environmental sources of covariation between educational attainment and pulmonary function with latent growth parameters were considered, the sources of covariation between the latent cognitive growth model parameters (i.e., intercept and slope) and both covariates were primarily genetic for ability level (intercepts) but environmental for rate of change (slopes). Such findings suggest that the forces important to timing or entry into cognitive decline may reflect stochastic processes or external environmental factors, primarily nonshared, that may differentially hasten cognitive decline in twins. These same forces may overlap with those that influence higher or lower educational attainment or those leading to better or worse pulmonary functioning.

Adult↗

PubMedDate not supplied

The metabolic syndrome mediates the relationship between cynical hostility and cardiovascular disease.

The objective of this work was to test the clustering of classic Cardiovascular disease (CVD) risk factors, known as the metabolic syndrome (e.g., increased blood pressure, insulin resistance, hypercholesterolemia combined with low levels of high-density lipoprotein, and abdominal fatness), as a mediator of the association between cynicism and CVD. Data were used from the Swedish Adoption/Twin Study of Aging (SATSA) (n = 1944 individuals, average age 62 years, 58% female). The cross-sectional association of cynicism with CVD was significant (standardized beta = 0.08, p <.01). In a longitudinal model, cynicism measured in 1984 was associated with CVD measured in 1987 (standardized beta = 0.06, p <.01). In a third model, a latent construct "metabolic syndrome" significantly partially mediated this relationship. Cynicism (measured 1984) predicted the metabolic syndrome (measured 1986-1988) (standardized beta = 0.20, p <.05) and the metabolic syndrome predicted CVD (measured 1987) (standardized beta = 0.18, p <.001); cynicism no longer significantly predicted CVD. Results were adjusted for baseline CVD, smoking, and age. These findings suggest that a clustering of CVD risk factors partially mediate the association between cynicism and CVD in an older population.

Age Factors↗

PubMedDate not supplied

Lifestyle risk and delaying factors.

Research findings suggest that dementia risk is lower in individuals with more extensive education, greater engagement in mentally stimulating leisure activities during adulthood, and higher occupational complexity. Other recent findings support the importance of early-life risk factors, such as socioeconomic conditions, early-life development, and exposure to infection, in explaining individual differences in dementia risk. Life-style variables have been conceptualized as delaying factors, postponing onset of dementia and thereby reducing total population burden of dementia. Using a sample of Swedish twins from the HARMONY study, we found that education significantly affects dementia onset, that is, occurrence and timing of dementia symptoms. In the HARMONY data, we also showed that differences in education are reflected in differences in leisure activities and occupation, suggesting that differences in cognitive engagement begin early and persist over the life course. Such findings point to the importance of taking a life-course perspective to designing interventions to delay or to prevent dementia.

Age of Onset↗

PubMedDate not supplied

Assessing age of dementia onset: validity of informant reports.

Age of onset is an important variable in Alzheimer research, yet remarkably little is known about its reliability and validity. The present study evaluated alternative methods for establishing age of onset for 297 individuals diagnosed with dementia through the HARMONY study. We compared two informant-based methods: a single question in a telephone screening interview and an in-depth, semi-structured, in-person interview. We then compared informant reports with medical records. The two informant-based methods yielded very similar results, r(297) = .89 (P < .0001). Informant reports were highly correlated with age of diagnosis in medical records, r(155) = .88 (P < 0.0001) for the single question, r(201) =.89 (P < .0001) for the in-depth interview. Age of diagnosis in the medical records lagged consistently 2.9 and 2.7 years behind age of onset from screening and in-depth interviews, respectively. Greater lag was associated with longer time since dementia onset, whether due to recall bias or improved detection of dementia. Lag was not influenced by dementia type, informant's relationship to proband, or proband's age. These findings suggest that informant reports of age of dementia onset are reliable and reasonably valid, even when only a single question is asked within the context of a larger interview.

Age of Onset↗