Biomedical subjects

N L Pedersen

Publications and source records attributed to N L Pedersen.

At least 55 records · Page 3Linked to original sources

PubMed1999

Primary megalencephaly at birth and low intelligence level.

OBJECTIVES: To evaluate the association between primary megalencephaly (PMG) at birth and psychosensory conditions and to determine mother-child similarity for PMG at birth. BACKGROUND: PMG is defined as a head circumference (HC) above the 98th percentile that most likely is due to brain enlargement and is not secondary to disease. Previously, PMG in children was reported to be associated with learning disabilities. Contradictory results regarding an association between PMG and intelligence in children exist. Many believe PMG expressed in childhood and adulthood may be inherited. METHODS: Birth records on HC from 144,273 boys, of whom 732 had PMG, were linked to data concerning intelligence level, mental retardation, and impairment of vision and hearing. A potential association between PMG at birth and mental retardation was also examined in 3,204 mentally retarded boys and girls. Parent-offspring similarity for PMG at birth was determined in 13,585 mother-child pairs. RESULTS: PMG was significantly associated with low intelligence level (odds ratio, 1.32; 95% confidence interval [CI], 1.11 to 1.38). The estimated odds ratio for mental retardation in PMG cases versus controls was 1.31 (95% CI, 0.80 to 2.02). There were no differences in frequencies of vision and hearing impairments between PMG cases and controls. Associations between mother's and child's birth weight-normalized HC (r = 0.14; p<0.0001) and PMG (odds ratio, 2.55; CI, 2.00 to 3.25) were found, supporting a multifactorial inheritance of PMG. CONCLUSIONS: PMG at birth is a risk factor for low intelligence level but not for vision and hearing impairments. The heritability of HC and PMG is moderate.

Adult↗

PubMed1999

Application of life table analysis to the onset of dementia in a genetically informative design.

The primary objective of this study was to estimate the survival function for time to onset of dementia in initially unaffected twins from when their partner (index proband) was diagnosed with dementia of the Alzheimer's type. Survival functions generated by life table analyses were compared by zygosity and gender. Sixty-one twin pairs where at least one member had been diagnosed with dementia of Alzheimer's type were included in the analyses. Additionally, both members of the twin pair had to be alive at the time the index proband was diagnosed with dementia. The probability of remaining cognitively intact within the first three years after the proband was diagnosed was high (0.93, 95% CI 0.89, 1.0), but after 15 years the probability of remaining intact was low (0.34, 95% CI 0.16, 0.52). Age of onset of the index proband was a significant covariate in the survival functions. There were significant differences in the survival functions for monozygotic (MZ) and dizygotic (DZ) co-twins (chi2 = 3.86, 1, P < 0.05), evidencing a genetic component for age of onset for dementia, but there were no significant differences between men and women.

Age of Onset↗

PubMed1999

Psychological and behavioral predictors of body fat distribution: age and gender effects.

OBJECTIVE: Abdominal fat has been shown to be associated with several adverse outcomes including diabetes, cardiovascular disease, and hypertension. Risk factors for abdominal fatness include genetic effects, age, and gender. Most recently, it has been hypothesized that psychological factors, as well as behavioral factors, may play a part in where fat is distributed. The purpose of this study was to assess the longitudinal predictive power of psychological variables (cynicism, anger, anxiety, and depression) measured in 1987 on waist-hip ratio (WHR) measured from 1992 to 1994 among different age and gender groups, as well as to test if alcohol consumption or smoking (measured in 1990) would mediate any of the relationships found. RESEARCH METHODS AND PROCEDURES: Data from the Swedish Adoption/Twin Study of Aging (n = 1392; average age: 58 years for middle-aged group and 74 years for older group; 58% female) were analyzed using a maximum-likelihood regression model where age, gender, and age by gender effects were assessed. RESULTS: Cynicism and anxiety predicted WHR in middle-aged subjects regardless of gender. Cynicism explained 2.5% of the variance in WHR and anxiety explained 1.7% of the variance in WHR. Anger predicted WHR in males regardless of age, explaining 4.0% of the variance; depression predicted WHR only in middle-aged females, explaining 2.0% of the variance. All analyses adjusted for body mass index, and neither alcohol consumption or smoking status mediated the relationships. DISCUSSION: These findings are suggestive with regard to the hypotheses that certain psychological states and behaviors may be associated with increased abdominal fatness.

Adipose Tissue↗

PubMed1999

Variation in blood concentrations of cadmium and lead in the elderly.

This study aims at characterizing blood concentrations of cadmium (B-Cd) and lead (B-Pb) in a group of 176 men and 248 women, 49-92 years of age (mean 68 years), selected from the Swedish Twin Registry. Metal concentrations were determined using graphite furnace atomic absorption spectrophotometry. B-Cd ranged from 0.05 to 6.8 microg Cd/L (median 0.36 microg Cd/L) and B-Pb from 5.6 to 150 microg Pb/L (median 27 microg Pb/L). As expected, smokers had higher B-Cd than nonsmokers (median 1.3 versus 0.32 microg Cd/L), while B-Pb was not significantly related to smoking habits. Among nonsmokers, women had higher B-Cd than men (median 0.35 versus 0.25 microg Cd/L). In men, but not women, B-Cd increased with age and consequently the gender-related difference in B-Cd was most obvious in the youngest age group. On the other hand, women had lower B-Pb than men (median 24 versus 30 microg Pb/L). In both men and women, B-Pb decreased between 50 and 70 years of age, perhaps reflecting decreased energy intake. In women, the highest B-Pb in the 50-55 years age group is probably related to an increased release of Pb from the skeleton during postmenopausal bone demineralization. After about 70 years, B-Pb tended to increase, which probably is a cohort effect due to much higher Pb exposure 10-30 years ago when leaded gasoline was used.

Aged↗

PubMed1999

The genetics of smoking persistence in men and women: a multicultural study.

Using a correlated liability dimensions model, we examined the extent to which the same genetic and environmental factors influence both initiation of regular cigarette smoking and maintenance of the smoking habit in men and women. We analyzed questionnaire survey data obtained from large samples of male and female like-sexed twins from three countries, Australia (N = 1535 pairs), Sweden (N = 5916 pairs), and Finland (N = 4438 pairs), subdivided into three age bands (18-25, 26-35, and 36-46 years of age). We found that familial influences on risk for persistence in smoking cannot be entirely explained by the same factors responsible for risk of smoking initiation. Total genetic variance for smoking persistence varied little by age band and sex (range, 39-49% in women and 42-45% in men); however, even among twins in the youngest group (18-25 years of age), who on average have the fewest years of cigarette use, less than 40% of the total genetic variance in smoking persistence was accounted for by the same genetic factors that increased risk of smoking initiation, and this percentage decreased to less than 10% in the 36-46 year olds.

Adolescent↗

PubMed1999

Genetic and behavioral risk factors for self-reported joint pain among a population-based sample of Swedish twins.

Self-reported joint pain, a typical manifestation of osteoarthritis, was examined using 335 twin pairs from the Swedish Adoption/Twin Study of Aging to estimate relative genetic and environmental influences on self-reported joint pain and to examine the relationships between joint pain, health behavior, and psychological variables. Findings suggest that family resemblance for self-reported joint pain represents similar environments more than genetic similarity. Data from the early 1970s, including exercise, physical activity at work, obesity, and neuroticism, were used to predict joint pain in 1993. For men, moderate amounts of exercise decreased the likelihood of joint pain, but strenuous amounts of physical activity in the workplace had the opposite effect. For women, exercise and physical activity were not significant predictors, but past obesity and higher levels of neuroticism increased the likelihood of reporting joint pain in 1993.

Aged↗

PubMed1999

Genetic and environmental influences on waist-to-hip ratio and waist circumference in an older Swedish twin population.

OBJECTIVE: To investigate the genetic and environmental influences on waist-to-hip ratio (WHR) and waist circumference (WC) measurements in males and females. DESIGN: Measurements taken from 1989-1991 as part of The Swedish Adoption/Twin Study of Aging (SATSA) were used for analysis. The SATSA sample contains both twins reared together as well as twins reared apart. SUBJECTS: 322 pairs of twins (50 identical, 82 fraternal male pairs and 67 identical, 123 fraternal female pairs); age range: 45-85y (average age, 65y). MEASUREMENTS: Waist-to-hip ratio (WHR), waist circumference (WC) and body mass index (BMI). RESULTS: In males, additive genetic effects were found to account for 28% of the variance in WHR and 46% of the variance in WC. In females, additive genetic effects were found to account for 48% of the variance in WHR and 66% of the variance in WC. The remaining variance in males was attributed to unique environmental effects (WHR, 72%; WC, 54%) and in females the remaining variance was attributed to unique environmental effects (WHR, 46%; WC, 34%) and age (WHR, 6%). When BMI was added into these models it accounted for a portion of the genetic and environmental variance in WHR, and over half of the genetic and environmental variance in WC. CONCLUSION: There are both genetic and environmental influences on WHR and WC, independent of BMI in both males and females, and the differences between the sexes are significantly different.

Aged↗

PubMed1999

Genetic effects on weight change and food intake in Swedish adult twins.

BACKGROUND: Obesity is influenced by genetic and environmental factors. Additionally, synergistic effects of genes and environments may be important in the development of obesity. OBJECTIVE: The aim of this study was to test for genetic effects on food consumption frequency, food preferences, and their interaction with subsequent weight gain. DESIGN: Complete data on the frequencies of consumption of 11 foods typical of the Swedish diet were available for 98 monozygotic and 176 dizygotic twin pairs aged 25-59 y who are part of the Swedish Twin Registry. The data were collected in 1973 as part of a questionnaire study. Body mass index was measured in 1973 and again in 1984. RESULTS: There was some evidence that genetic effects influenced the frequency of intake of some foods. Similarity among monozygotic twins exceeded that among dizygotic twins for intake of flour and grain products and fruit in men and women, intake of milk in men, and intake of vegetables and rice in women, suggesting that genes influence preferences for these foods. Analyses conducted for twins reared together and apart also suggested greater monozygotic than dizygotic correlations, but cross-twin, cross-trait correlations were all insignificant, suggesting that the genes that affect consumption frequencies are not responsible for mediating the relation between the frequency of intake and weight change. CONCLUSIONS: Genetic effects and the frequency of intake are independently related to change in body mass index. However, there was no suggestion of differential genetic effects on weight gain that were dependent on the consumption frequency of the foods studied.

Adult↗

PubMed1999

Implications of body fat distribution in an older twin population.

BACKGROUND: As people age, fat becomes preferentially deposited in the abdominal region over the periphery, and such changes are thought to be associated with adverse metabolic outcomes. We were interested in whether body mass index (BMI) and waist-hip ratio (WHR) are differentially associated with fasting insulin levels, triglycerides, and blood pressure (systolic and diastolic) in an older population. We were also interested in whether these associations change after controlling for genetic influences. METHODS: Data were obtained as part of the Swedish Adoption/Twin Study of Aging. All blood samples and anthropometric measures were assessed from 1989-1991 except insulin, which was assessed from 1986-1988. The sample contains 263 twin pairs (97 monozygotic and 166 dizygotic), 56% women, average age 65 years. RESULTS: In men and women, WHR and BMI were significantly associated with all the metabolic variables except for diastolic blood pressure. When BMI's association with the metabolic variables was assessed independent of WHR, it remained significantly associated with all metabolic variables except diastolic blood pressure in men and triglycerides in women. When WHR's association with the metabolic variables was assessed independent of BMI, it did not remain significantly associated with any of the metabolic variables in men and remained significantly associated with insulin and diastolic pressure in women. After controlling for genetic effects, the relationship between WHR and the metabolic variables became nonsignificant. However, BMI remained significantly associated with systolic blood pressure and triglycerides in men, independent of WHR. CONCLUSION: The results suggest that overall body fat is important to consider in relation to these metabolic parameters in older individuals. The results also suggest that BMI may share associations with blood pressure and triglycerides beyond those that can be attributed to familial influences.

Adipose Tissue↗

PubMed1999

Origins of individual differences in episodic memory in the oldest-old: a population-based study of identical and same-sex fraternal twins aged 80 and older.

The relative importance of genetic and environmental influences on episodic memory in very late life was studied using a quantitative genetic approach. Identical (n = 125) and same-sex fraternal (n = 157) twin pairs, aged 80 and older (mean age = 83.3; SD = 3.1) and without a diagnosis of dementia were tested with seven memory measures: (1-2) Digit Span Forward and Backwards, (3) Prose Recall, (4) Thurstone's picture memory test, and the Memory in Reality (MIR) test, including the subtasks of (5) free recall, (6) recognition, and (7) relocation. Heritabilities, estimated by structural equation modeling, ranged from .04 to .49. The digit span backward test showed the highest heritability (h2 = .49), while heritabilities were typically lower for the long-term memory measures. The results demonstrate genetic influences on memory in the oldest-old, but suggest that the magnitude of these effects differs across memory measures.

Aged↗

PubMed1999

History of depression and other psychiatric illness as risk factors for Alzheimer disease in a twin sample.

Although case-control studies have found elevated risk for Alzheimer disease (AD) associated with a prior psychiatric history, most of the previous research had inadequate controls for familial risk factors. Putative psychiatric risk factors were evaluated for a registry-based sample of 65 twin pairs discordant for AD. Risk ratios were calculated for psychiatric illness at any time and for episodes more than 10 years before dementia onset. Prior psychiatric illness was significantly associated with elevated risk. Most of these cases represented depressive episodes. When analyses were restricted to individuals whose mental illness commenced more than 10 years before dementia onset, the magnitude of the odds ratio decreased markedly. These findings suggest that a history of psychiatric illness, especially depression, may be associated with an elevated risk for AD. In particular, these results are consistent with an interpretation that symptoms of depression and similar complaints represent prodromal phases of dementia.

Aged↗

PubMed1999

The importance of genetic and environmental effects for self-reported health symptoms: a 30-year follow-up considering survival and selection effects.

OBJECTIVES: This study delineated the nature of individual differences in self-reported health status across a 30-year period. Potential survival and selection effects on mean levels, variances, and genetic and environmental sources of variance were evaluated. METHODS: Self-reported health status in 1963 was evaluated in 5,229 pairs of twins from the Swedish Twin Registry and in a subsample of 351 pairs surviving to the age of 80 years in 1993. Structural equation modeling evaluated genetic and environmental contributions to total variance and change in variance. RESULTS: For men but not women, the genetic and environmental influences on health symptoms differed between survivors and nonsurvivors. Total variance increased, reflecting an increase in environmental variance, across the 30 years for both genders. Genetic variance decreased longitudinally for men. DISCUSSION: The increase in variation from the mid-50s to the mid-80s appears to be due to an accumulation in environmental variation. There are gender differences that deserve further exploration.

Age Factors↗

PubMed1999

Genetic effects for plasma factor VII levels independent of and in common with triglycerides.

BACKGROUND: Coagulation factor VII has been demonstrated as a potential risk factor for cardiovascular disease. Both genes and non-genetic factors are related to plasma levels of factor VII. However, the extent to which genetic effects influence variability in plasma factor VII levels is unknown. Further, increased levels of plasma factor VII are associated with serum triglycerides, yet the reason for this association is not fully understood. METHODS AND RESULTS: Quantitative genetic analyses were applied to evaluate the relative importance of genetic and different environmental influences on plasma factor VII levels and to test the significance of genetic and environmental factors in common to factor VII and triglycerides in 215 pairs of middle-aged and elderly twins, of whom 104 were reared apart and 120 were women. Genetic influences were found to account for 57% of the individual differences in plasma factor VII levels, whereas shared-rearing and residual-familial environmental factors were not significant. Furthermore, a significant genetic correlation of 0.38 was found between factor VII and triglycerides, but the environmental correlation between these two measures was not significant. Genetic factors in common to factor VII and triglycerides explain about 7% of the total variance for factor VII. CONCLUSION: The present study suggests that there are substantial genetic influences on plasma factor VII levels. Furthermore, genetic effects explain the phenotypic association between factor VII and triglycerides.

Aged↗

PubMed1998

Co-twin study of the effect of environment and dietary elements on acquisition of Helicobacter pylori infection.

The rate of Helicobacter pylori infection is inversely related to socioeconomic status, and childhood is thought to be the major acquisition period. The authors investigated the importance of childhood environment in the acquisition of H. pylori infection. A cross-sectional study was conducted of monozygotic and dizygotic twins who were reared apart or reared together. Three hundred twins from a subregistry of the Swedish Twin Registry were studied. H. pylori status was evaluated by using an enzyme-linked immunosorbent assay for anti-H. pylori immunoglobulin G. Socioeconomic status during childhood was assessed on the basis of the density of the living conditions and the economic situation of the family that reared the twins. Current socioeconomic status was estimated by using a scale that combined income and education. Dietary elements that were studied included fat and fiber intake and ascorbic acid consumption. The density of the childhood home was consistently found to be significantly associated with the acquisition of H. pylori infection (p = 0.04). Among monozygotic twins reared apart and discordant for H. pylori status, affected twins were raised in homes under poorer socioeconomic conditions than those of their unaffected co-twins (p = 0.02). Additionally, infected twins consumed more ascorbic acid than their unaffected co-twins (p = 0.04). The finding of an effect of socioeconomic status during childhood on the acquisition of H. pylori among monozygotic twins who were reared apart and had an identical genetic makeup but not a common environment confirms the hypothesis that childhood acquisition of H. pylori infection is linked to hygiene practices.

Adult↗

PubMed1998

[Genetic factors are often found inl Alzheimer disease. An extensive twin study to clarify the heredity-environment relationship].

Genetic and environmental risk factors are central concerns in dementia research. Through twin studies one can study the relative importance of genetic and environmental risk factors. One such study, based on the Swedish Twin Registry, shows that genetic effects are of considerable importance for developing Alzheimer's disease, even late in life, but that environmental factors are also important. For vascular dementia, the results indicate that non-genetic factors are of primary importance.

Aged↗

PubMed1998

Latent class analysis of temperance board registrations in Swedish male-male twin pairs born 1902 to 1949: searching for subtypes of alcoholism.

BACKGROUND: Alcoholism is clinically heterogeneous. We have attempted to identify and validate subtypes of broadly defined alcoholism. METHODS: Latent class analysis (LCA) was applied to data on the number, age at onset and reasons for temperance board registration (TBR) in all male-male twin pairs of known zygosity born in Sweden from 1902-1949. RESULTS: Of the five classes identified, two were relatively common: single-cause registrant-drunk (SCR-D); and early-onset multiple-cause registrant (EO-MCR). In contrast to the SCR-D class, the EO-MCR class was characterized by: (i) earlier age at first TBR; (ii) higher number of TBRs; (iii) TBRs for drunk driving and alcohol-related crimes; (iv) much higher risk for alcohol-related imprisonment and hospitalization; (v) higher levels of neuroticism and novelty-seeking; and (vi) much greater risk for TBR in co-twins. In twin pairs concordant for TBR, concordance for LCA-derived class assignment far exceeded chance expectation, more so in monozygotic than in dizygotic pairs. CONCLUSIONS: Alcoholism is aetiologically as well as clinically heterogeneous. The two most common subtypes identified in these analyses bear substantial but imperfect resemblance to previously proposed typologies.

Alcoholism↗

PubMed1998

Longitudinal and cross-sectional twin data on cognitive abilities in adulthood: the Swedish Adoption/Twin Study of Aging.

Cross-sequential methods of analysis, designed to separate age and cohort effects, were applied to data from the Swedish Adoption/Twin Study of Aging. Thirteen cognitive variables were collected at 3 times of measurement separated by 3-year intervals. Data were available from 85 individuals from monozygotic (MZ) pairs reared apart, 132 from MZ pairs reared together, 207 from dizygotic (DZ) pairs reared apart, and 178 from DZ pairs reared together (age range at first assessment: 41-84 years). Time x Cohort interactions were found for mean performance on 8 of the measures, revealing stable mean performance in the younger cohorts and longitudinal decreases in mean performance in the older cohorts. Cohort and time effects for total variance were mixed; little evidence was found for increases in variance with age. Age changes and cohort differences in genetic and environmental components of variance were test-specific; several Cohort x Time interactions attained significance. Heritability of the general cognitive ability factor showed significant longitudinal decreases over time in the older cohorts.

Adolescent↗

PubMed1998

Childhood adoption: long-term effects in adulthood.

Clinicians and researchers have characterized early life experiences as permanent and stable influences on the personality and subsequent life experiences of an individual. Recent conceptualizations have suggested that personal and environmental factors influencing development are not deterministic. Multiple pathways into adulthood are possible. Adoption is one potential early life stressor that may illustrate the usefulness of such conceptualizations for assessing long-term effects in adulthood. Previous studies of adoption have characterized the effects of adoption into adolescence and young adulthood. The purpose of this study was to provide an initial assessment of the long-term impact of adoption. The participants were taken from the Swedish Adoption/Twin Study of Aging. From the original sample, we identified a subsample of 60 pairs of twins who were separated and reared apart, with one member being raised by a biological parent or parents and the other by an adoptive parent or parents with no biological relationship. A series of univariate and multivariate analyses were undertaken to assess the elements associated with being reared in either an adoptive home or the home of biological parent(s). The results suggest few significant effects of adoption on the adult adjustment of adoptees. In particular, the results reflect the important mediating role of childhood socioeconomic status, suggesting that the stress of adoption itself is mediated by the type of rearing environment provided by the adoption process.

Adaptation, Psychological↗