Biomedical subjects

Stig Berg

Publications and source records attributed to Stig Berg.

At least 19 recordsLinked to original sources

PubMed2006

Role of genes and environments for explaining Alzheimer disease.

CONTEXT: Twin studies using selected samples have shown high heritability for Alzheimer disease (AD). OBJECTIVE: To evaluate genetic and environmental influences on AD in a fully ascertained population of older twins, including like- and unlike-sex pairs. DESIGN: Five-group quantitative genetic model: male monozygotic twins, female monozygotic twins, male dizygotic twins, female dizygotic twins, and unlike-sex twins. SETTING AND PARTICIPANTS: All twins in the Swedish Twin Registry aged 65 years and older. The study included 11,884 twin pairs, among whom were 392 pairs in which 1 or both members had AD. MAIN OUTCOME MEASURES: All individuals were screened for cognitive dysfunction. Suspected cases of dementia and their co-twins received complete clinical diagnostic evaluations for AD. Estimates of heritability, shared environmental influences, and nonshared environmental influences, adjusting for age, were derived from the twin data. RESULTS: Heritability for AD was estimated to be 58% in the full model and 79% in the best-fitting model, with the balance of variation explained by nonshared environmental influences. There were no significant differences between men and women in prevalence or heritability after controlling for age. Within pairs concordant for AD, intrapair difference in age at onset was significantly greater in dizygotic than in monozygotic pairs, suggesting genetic influences on timing of the disease. CONCLUSIONS: In the largest twin study to date, we confirmed that heritability for AD is high and that the same genetic factors are influential for both men and women. However, nongenetic risk factors also play an important role and might be the focus for interventions to reduce disease risk or delay disease onset.

Age of Onset↗

PubMed2006

Sex differences after all those years? Heritability of cognitive abilities in old age.

We investigated sex differences in genetic and environmental effects on cognitive abilities among older adult twins. We drew participants from the Swedish Twin Registry; our sample included 647 twin pairs. Our cognitive measures included Synonyms, Block Design, Digit Span, Thurstone's Picture Memory, Symbol Digit, and general cognitive ability tests. Higher age was related to lower performance in all cognitive measures, except synonyms. For digit span forward, symbol digit, and general cognitive ability tasks, there was a Sex x Age interaction, with greater deficits in the performance of women compared with those of men at higher ages. We found no sex-specific genetic influences. In other words, the same genetic effects were operating for men and women. Furthermore, the magnitude of genetic effect was similar for men and women.

Adoption↗

PubMed2006

Satisfaction with present life predicts survival in octogenarians.

We examined the effect of life satisfaction on survival over 10 years among 80-year-old and older same-sex twins of whom 320 individuals responded to the Life Satisfaction Index Z questionnaire in connection with the OCTO-Twin study. We treated participants as individuals in semiparametric Cox regression mixed-effects models (frailty) by adjusting the similarity of mortality risk within twin pairs by modeling it as a random variable. An exploratory factor analysis yielded three factors: Zest and Mood represented satisfaction with present life and Congruence represented satisfaction with past life. Those in the lowest quartile of factors of satisfaction with present life had an almost twofold risk for mortality compared with those in the highest quartile, even after adjustment for multiple confounders. Satisfaction with past life satisfaction showed no association with mortality.

Aged, 80 and over↗

PubMed2006

Effects of repeated testing in a longitudinal age-homogeneous study of cognitive aging.

Estimates of gains related to repeated test exposure (retest effects) and within-person cognitive changes are confounded in most longitudinal studies because of the nonindependent time structures underlying both processes. Recently developed statistical approaches rely on between-person age differences to estimate effects of repeated testing. This study, however, demonstrates how retest effects can be evaluated at the group level in an age-homogeneous population-based study by use of a sampling-based design approach in which level and change of cognitive performance of previous participants, measured at ages 70, 75, 79, 81, 85, 88, 90, 92, 95, 97, and 99 years, were compared with performances of survivors of a representative sample identified and drawn from the same original population cohort but invited for the first time at age 85 with subsequent measurements at ages 88, 90, 92, 95, 97, and 99. The comparisons revealed a trend toward retest effects on two out of five cognitive measurements. The study demonstrates how a design-based approach can provide valuable insights into continuous learning processes embedded in population average aging trajectories that are not confounded with cohort and mortality-related selective attrition.

Aged↗

PubMed2006

Surprising lack of sex differences in normal cognitive aging in twins.

Sex differences in the etiology of normal cognitive functioning in aging remain largely unexplored. We conducted an investigation of genetic and environmental contributions to sex differences in level of cognitive performance and rate of decline in the Swedish Adoption/Twin Study of Aging (SATSA) (Finkel & Pedersen, 2004) data set. Behavioral genetic parameterizations of a latent growth curve model were fit to longitudinal data on 11 cognitive measures. Seven hundred and ninety-eight non-demented individuals had cognitive data across four waves of measurement covering 13 years. Participants ranged in age from 44 to 88 at first testing wave; 60% were female. Results indicated sex differences in mean performance for five cognitive measures and in rates of decline for Information and Card Rotations. Only Synonyms demonstrated sex differences in genetic and environmental contributions to mean performance: heritability was higher in men than women. Despite differential longevity and susceptibility to disease, there are no consistent indications that men and women show different patterns of cognitive aging.

Adult↗

PubMed2005

Complete ascertainment of dementia in the Swedish Twin Registry: the HARMONY study.

The purpose of this report is to describe the Study of Dementia in Swedish Twins (known as HARMONY), including procedures for complete ascertainment of all cases of Alzheimer's disease (AD) and other dementias in 14,435 individuals aged 65 and older from the national Swedish twin registry. Telephone cognitive screening identified 11.5% as positive for cognitive dysfunction. Clinical diagnoses were completed for 1557 individuals, including individuals who screened positive, their twin partners, and a sample of normal controls. Estimated prevalence of dementia ranged from 1.4% for age 65-69 to 29.2% for age 90 and older. Concordance rates for Alzheimer's disease were 59% for monozygotic twins, 32% for like-sexed, and 24% for unlike-sexed dizygotic twins. Among monozygotic twins where both twins had Alzheimer's disease, the within pair difference in age of onset ranged from both becoming demented in the same year to 7 years difference in onset.

Age Factors↗

PubMed2005

Quantitative genetic analysis of latent growth curve models of cognitive abilities in adulthood.

Though many cognitive abilities exhibit marked decline over the adult years, individual differences in rates of change have been observed. In the current study, biometrical latent growth models were used to examine sources of variability for ability level (intercept) and change (linear and quadratic effects) for verbal, fluid, memory, and perceptual speed abilities in the Swedish Adoption/Twin Study of Aging. Genetic influences were more important for ability level at age 65 and quadratic change than for linear slope at age 65. Expected variance components indicated decreasing genetic and increasing nonshared environmental variation over age. Exceptions included one verbal and two memory measures that showed increasing genetic and nonshared environmental variance. The present findings provide support for theories of the increasing influence of the environment with age on cognitive abilities.

Adoption↗

PubMed2005

Life on the edge: patterns of formal and informal help to older adults in the United States and Sweden.

OBJECTIVE: Our objective in this study was to compare assistance received by individuals in the United States and Sweden with characteristics associated with low, moderate, or high 1-year placement risk in the United States. METHODS: We used longitudinal nationally representative data from 4,579 participants aged 75 years and older in the 1992 and 1993 waves of the Medicare Current Beneficiary Survey (MCBS) and cross-sectional data from 1,379 individuals aged 75 years and older in the Swedish Aging at Home (AH) national survey for comparative purposes. We developed a logistic regression equation using U.S. data to identify individuals with 3 levels (low, moderate, or high) of predicted 1-year institutional placement risk. Groups with the same characteristics were identified in the Swedish sample and compared on formal and informal assistance received. RESULTS: Formal service utilization was higher in Swedish sample, whereas informal service use is lower overall. Individuals with characteristics associated with high placement risk received more formal and less informal assistance in Sweden relative to the United States. DISCUSSION: Differences suggest formal services supplement informal support in the United States and that formal and informal services are complementary in Sweden.

Aged↗

PubMed2004

Comorbid type 2 diabetes mellitus and hypertension exacerbates cognitive decline: evidence from a longitudinal study.

BACKGROUND: diabetes and hypertension are two highly prevalent diseases in the old population. They are highly related such that comorbidity is common. OBJECTIVES: to examine (i) the independent impact of the respective diseases on cognitive decline in very old age and (ii) the interactive impact of the two diseases on cognitive decline. SUBJECTS: 258 individuals (mean age = 83 years), all non-demented at baseline. Of these, 128 individuals (non-cases) were free from diabetes and hypertension, 92 individuals had a diagnosis of hypertension, 16 had a type 2 diabetes mellitus diagnosis without hypertension, and 22 had comorbid diabetes and hypertension. METHOD: a population-based longitudinal study of ageing (The OCTO-Twin Study), including four measurement occasions 2 years apart. The Mini-Mental State Examination was used to measure general cognitive function. Data were analysed using SAS Proc Mixed multilevel modelling. RESULTS: longitudinal trajectories indicated a steeper decline in cognitive function related to diabetes but not related to hypertension. However, the results indicated greatest cognitive decline among persons with comorbid diabetes and hypertension. CONCLUSIONS: it is concluded that comorbidity of diabetes and hypertension produce a pronounced cognitive decline. This finding emphasises the importance of prevention and treatment of those highly prevalent diseases in the old population.

Aged↗

PubMed2004

Laxative treatment elevates plasma homocysteine: a study on a population-based Swedish sample of old people.

OBJECTIVES: Elevated plasma homocysteine might indicate an increased risk of cancer, and cardiovascular and neurological diseases. The homocysteine level depends on the supply of folate and cobalamine, and constipation and/or laxative treatment might compromise this supply. The present study examined the impact of constipation and laxative treatment on the blood levels of homocysteine, folate and cobalamine in a population-based sample of aged people, including consideration of frailty and impaired renal function, both of which may also influence the homocysteine level. METHODS: The study was based on biochemical tests in 341 females and 183 males aged 82 years or older. The concentrations of homocysteine (plasma), folate, cobalamine and urea (serum) were measured in subjects with and without ongoing treatment with laxative drugs. Values were adjusted for age, gender and frailty, as well as for clinical diagnoses and drug therapies known to affect homocysteine levels. RESULTS: Homocysteine levels were increased and those of folate reduced in aged subjects on laxatives. Homocysteine remained elevated after adjusting for frailty and various neurological disorders. There was no significant effect on homocysteine and folate in constipated subjects without laxatives.

Aged↗

PubMed2004

How heritable is Alzheimer's disease late in life? Findings from Swedish twins.

Although genetic effects are known to be important for early onset Alzheimer's disease, little is known about the importance of genetic effects for late-onset disease. Furthermore, previous studies are based on prevalent cases. Our purpose was to characterize the relative importance of genetic and environmental factors for incident Alzheimer's disease late in life, and to test for differences in the importance of genetic effects at different ages. A cohort of 662 pairs of Swedish twins 52 to 98 years of age who were without symptoms of dementia was followed up for an average of 5 years. Incident dementia cases were detected through follow-up at 2 to 3-year intervals using either cognitive testing or telephone screening followed by dementia workups. A physician, psychologist, and nurse gave consensus diagnoses. During the follow-up period, 5.8% of the sample was diagnosed with Alzheimer's disease. Average age of onset was 83.9 years (standard deviation, 6.3). Of the 26 monozygotic pairs in which at least one twin developed Alzheimer's disease, 5 were concordant (probandwise concordance, 32.2%). The concordance rate for dizygotic pairs was 8.7% (2 of 44 pairs). Structural model fitting indicated that 48% of the variation in liability to Alzheimer's disease could be attributed to genetic variation. Estimates did not differ significantly between twins younger than age 80 years and those older than age 80 years at baseline. Although these genetic estimates for incident disease are lower than those for prevalent disease, the importance of genetic factors for liability to Alzheimer's disease is considerable even late in life.

Age Factors↗

PubMed2004

Type 2 diabetes mellitus contributes to cognitive decline in old age: a longitudinal population-based study.

We examined change in neuropsychological test performance related to type 2 diabetes mellitus across a 6-year interval. A population-based sample of 274 elderly participants (36 with diabetes and 238 without diabetes) was examined at four occasions at a 2-year interval. The participants were 80-93 years of age (M = 82.8 years) and without dementia at baseline. The test battery included tests of speed, visuospatial ability, short-term memory, semantic memory, episodic memory, and the Mini Mental Status Examination. Several models, taking into account diabetes and demographic data, were analyzed using SAS Proc Mixed multilevel modeling. At baseline, there were no significant differences in the neuropsychological tests related to diabetes. The longitudinal analyses, however, showed that diabetes was a significant predictor of decline for many of the tests. These findings points to the conclusion that type 2 diabetes is associated with accelerated cognitive decline in old age that may result in dementia.

Age Factors↗

PubMed2004

Change in cognitive capabilities in the oldest old: the effects of proximity to death in genetically related individuals over a 6-year period.

Change in cognitive abilities was assessed over a 6-year period in a sample of monozygotic and same-sex dizygotic twin pairs (N = 507 individuals), aged 80 and older (mean age = 83.3 years: SD = 3.1). who remained nondemented over the course of the study. Latent growth models (LGMs) show that chronological age and time to death are consistent predictors of decline in measures of memory, reasoning, speed, and verbal abilities. Multivariate LGM analysis resulted in weak and often negative correlations among rates of change between individuals within twin pairs, indicating greater differential change within twin pairs than occurs on average across twin pairs. These findings highlight several challenges for estimating genetic sources of variance in the context of compromised health and mortality-related change.

Aged↗

PubMed2004

Pain perceptions of the oldest old: a longitudinal study.

PURPOSE: This study assessed self-reported pain in the oldest old and examined its changes over time and in relation to other measures of health and functioning. DESIGN AND METHODS: A population-based sample of the oldest old (86-92 years of age) residing in Sweden who were participating in a multiwave longitudinal investigation were interviewed about their experience of pain, as well as other dimensions of health and functioning. RESULTS: Prevalence of pain at baseline was 34% and rose to 40% at follow-up. Incidence of new pain cases during that period was 16 percent. Pain was significantly related to sleep difficulties, medication usage, global subjective health, depressive symptoms, and mobility, though the magnitude of the associations was relatively small. IMPLICATIONS: Our results extend previous cross-sectional findings by demonstrating there is both an increase in the proportion of people reporting pain over time after the age of 85 as well as the possibility of recovery. The modest strength of associations of pain with other areas of functioning suggests adaptation and selectivity among survivors in very late life.

Aged↗

PubMed2004

The genetic and environmental effects on depressive symptoms among older female twins.

The aim of the present study was to examine the contribution of genetic and environmental factors to depressive symptoms among older women. The participants were 102 monozygotic and 115 dizygotic female twin pairs aged 64 to 76 years. Depressive symptoms were assessed by the Center for the Epidemiologic Studies Depression Scale. The contribution of genetic and environmental effects was estimated for the constructed depressiveness factor and for the subscales which were depressed mood, psychomotor retardation, lack of wellbeing and interpersonal difficulties. Of the variance in depressiveness, shared environmental influences accounted for 39% and nonshared environmental influences 61%. For the subscales, 24% to 62% of the variance was explained by individual, and 13% to 23% by shared, environmental factors. Lack of wellbeing had its own moderate additive genetic effect explaining 30% of the variance. This study showed that in older women predominantly environmental factors underlay individual differences in depressiveness; however, the factors varied to some extent between dimensions measured by the subscales.

Aged↗

PubMed2003

Does aspirin protect against Alzheimer's dementia? A study in a Swedish population-based sample aged > or =80 years.

OBJECTIVE: It has been reported that aspirin and other non-steroidal anti-inflammatory drugs (NSAID) may protect against dementia of Alzheimer's type and/or vascular dementia. However, co-morbidity and the dose of aspirin may be critical. A major indication for low-dose aspirin is prophylaxis after stroke and transient ischaemic attacks, conditions that may obscure an anti-dementia effect by the drug. Alternatively, low-dose aspirin may be insufficient if the protective effect is due to an anti-inflammatory mechanism. The aim of this study was to assess whether high-dose or low-dose aspirin may protect against Alzheimer's dementia in subjects aged > or =80 years. For comparison, effects of (other) NSAID, paracetamol and D-propoxyphene were studied. METHODS: Global, cross-sectional, and longitudinal (1991-2000) epidemiological analyses of clinical, cognitive and drug treatment data on 702 individuals 80 years old or more (351 twin pairs of same sex), all alive at inclusion: mean age 83.9 years (80-99 years). Calculations were made with logistic regression of associations between use of various analgesics and cognitive function, after adjustment for age, gender, and cardiovascular and cerebrovascular diseases. RESULTS: Users of high-dose aspirin had significantly lower prevalence of Alzheimer's dementia and better-maintained cognitive function than non-users. There were numerically similar but not significant associations with use of low-dose aspirin and other NSAID. There were no such associations with use of either paracetamol or D-propoxyphene. CONCLUSION: Aspirin might protect against Alzheimer's disease, but controlled trials are warranted.

Acetaminophen↗

PubMed2003

The influence of mortality on twin models of change: addressing missingness through multiple imputation.

Twin analyses of phenotypes that are associated with mortality may provide biased heritability estimates if the models require that data from both members of a pair are available. This is particularly true when longitudinal analyses are applied to measures of cognition or biomarkers of aging. The effect of applying imputational techniques that include information on age at death was tested on longitudinal data from two twin studies of aging, each with up to four occasions of measurement. Measures of twin similarity for intercepts and slopes from three latent growth curve models were compared: without imputed data, including imputed data but without information on age at death, and including imputed data with information on age at death. Results indicated that twin similarity for slopes decreases when mortality is accounted for, but that considerable age-related covariation remains.

Humans↗

PubMed2003

Genetic and environmental influences on decline in biobehavioral markers of aging.

Latent growth models were applied to longitudinal twin data on markers of aging to investigate genetic and environmental influences on the processes of change with age. The sample included 1957 participants aged 50 to 96 years. Five markers were assessed: forced expiratory volume, mean arterial pressure, grip strength, motor functioning, and well-being. Data were gathered at up to three follow-up occasions at intervals of 3 years. Results indicated monotonic changes with age for all but two variables. Performance on motor functioning and well-being was stable until age 65 or 70, followed by significant decline. Genetic influences on the level of performance were indicated for all five markers of aging. Genetic influences on the slope were found for only three of the variables: motor functioning, mean arterial pressure, and forced expiratory volume. Investigations of the aging process will differ depending on whether the focus is on static performance or change.

Aged↗