Biomedical subjects

S O Samuelsen

Publications and source records attributed to S O Samuelsen.

At least 19 recordsLinked to original sources

PubMed2006

Association between level of physical activity and lung function among Norwegian men and women: the HUNT study.

OBJECTIVE: To estimate the association between level of physical activity in 1984-1986 and 1995-1997 and lung function in 1995-1997 among Norwegian men and women aged 28-80 years. DESIGN: In 1984-1986 and 1995-1997, all residents of Nord-Trøndelag County, Norway, aged > or =20 years were invited to participate in the Nord-Trøndelag Health Studies. These analyses included a sample that took part in both studies and underwent spirometry (n = 8047). We used linear regression models adjusting for potential confounders stratified by sex and age groups (28-49 years, 50-69 years and > or =70 years) to estimate the association between forced expiratory volume in 1 second (FEV1) and physical activity. RESULTS: Men and women who were physically active in 1985 and 1995 had the highest lung function in both sexes and in all age groups. The reduction in FEV1 ranged from 20 ml to 170 ml, similar to 1-7% of predicted values dependent on physical activity level. Lung function was also associated with body mass index (BMI), height, smoking and subjective health. CONCLUSIONS: The findings show that a high level of physical activity corresponds to about 3-5 years of normal decline in FEV1 (30 ml/year), and may therefore overcome the disadvantages of a decline in FEV1 from increasing age.

Adult↗

PubMed2005

A simple correction for ties when censoring times depend on covariates.

We point out that the conventional methods for ties correction may be seriously biased when censoring times depend on covariates. A simple modification to the Efron correction method is suggested which works remarkably well in simulation studies. The method corresponds closely to breaking ties by random ordering. The modified correction method is easy to implement and computationally no more demanding than the Efron correction.

Adolescent↗

PubMed2005

Cesarean delivery and cow milk allergy/intolerance.

The present study provides support for a positive association between cesarean delivery and persistent cow milk allergy/cow's milk intolerance. Correspondingly, a negative association was seen between cesarean delivery and early outgrown cow milk allergy/intolerance. A possible explanation is that cesarean delivery, rather than increasing the overall risk of food allergy, increases the risk of persistency of disease among food allergic children.

Cesarean Section↗

PubMed2002

Depression in postpartum and non-postpartum women: prevalence and risk factors.

OBJECTIVE: The aim of the study was to assess the prevalence of depression in postpartum women as compared with non-postpartum women, and to identify risk factors of depression in both groups. METHOD: A population based questionnaire study was performed among women 18-40 years in two municipalities in Norway in 1998-1999. A total of 2,730 women were included, of whom 416 were in the postpartum period. RESULTS: The prevalence of depression was higher in non-postpartum as compared with postpartum women. High scores on the life event scale, a history of depression and a poor relationship to the partner were associated with depression in both postpartum and non-postpartum women. When controlling for the identified risk factors of depression the odds-ratio for depression in the postpartum period was 1.6 (95% CI: 1.0-2.6). CONCLUSION: The risk for depression was increased in the postpartum period, when controlling for the uneven distribution of risk factors.

Adult↗

PubMed2002

Feasibility of measuring lung function in preschool children.

BACKGROUND: There have been difficulties in applying spirometric tests to children of preschool age. METHODS: The feasibility of measuring lung function was examined in 652 children aged 3-6 years using dynamic spirometry with an animation programme and the guidelines approved by the European Respiratory Society. RESULTS: Data from 603 (92%) children with at least two acceptable forced expiratory manoeuvres were analysed; 408 (68%) achieved at least three acceptable manoeuvres. Children with only two acceptable manoeuvres were younger, shorter, and weighed less (p<0.001). The lower levels of lung function in this group were partly explained by body size. 63% of those with three acceptable manoeuvres had a difference of </=5% between the highest and second highest forced expiratory volume in 1 second (FEV(1)); when a difference of </=10% was applied, 91% of the children were included. A similar trend was seen for forced vital capacity (FVC). The acceptability and reproducibility increased with increasing age, and levels of lung function increased linearly with age. The linear regression model showed that standing height was a satisfactory predictor of lung function; the explained fraction of variance (R(2)) was 59% for FEV(1). Most FVC manoeuvres in children older than 3 years were acceptable and reproducible. CONCLUSIONS: Spirometric testing is feasible in preschool children and may be useful for both clinical practice and research. This study may fill the deficiency in reference values for European preschool children.

Aging↗

PubMed2001

Review of validation studies of the Edinburgh Postnatal Depression Scale.

OBJECTIVE: To review validation studies of the Edinburgh Postnatal Depression Scale (EPDS). METHOD: A systematic search was performed in Medline and the Science Citation Index Expanded (ISI) from the period 1987-2000. For sensitivity and specificity of the EPDS presented in each study, 95% confidence intervals were estimated. Positive and negative predictive values were estimated assuming prevalences of postpartum depression ranging from 5% to 20%. RESULTS: Eighteen validation studies were identified. The study design varied between studies. The sensitivity and specificity estimates also varied: 65-100% and 49-100%, respectively. The confidence intervals were estimated to be wide. Our estimates suggest a lower positive predictive value in a normal population than in the validation study samples. CONCLUSION: Most studies show a high sensitivity of the EPDS. Because of the differences in study design and large confidence intervals, uncertainty remains regarding the comparability between the sensitivity and specificity estimates of the different EPDS versions.

Confidence Intervals↗

PubMed2001

Changing paternity and time since last pregnancy; the impact on pre-eclampsia risk. A study of 547 238 women with and without previous pre-eclampsia.

BACKGROUND: Long time interval between pregnancies has been found to increase the risk of pre-eclampsia in second pregnancy. Our aim was to investigate whether this effect is influenced by a history of pre-eclampsia or a change in paternity. METHODS: We studied 547 238 women with a first and second pregnancy registered in the Medical Birth Registry of Norway, 1967-1998. The relative risk of pre-eclampsia in the second delivery according to time interval between deliveries was estimated as odds ratios (OR) in logistic regression models, controlling for changing paternity, maternal age and calendar time period in women with and without previous pre-eclampsia. RESULTS: A change of paternity for the second pregnancy was associated with a reduced risk of pre-eclampsia after controlling for the time since first delivery (adjusted OR = 0.80, 95% CI : 0.72-0.90), but the interaction between change in paternity and time between deliveries was significant only for women with no previous pre-eclampsia. The interaction between history of pre-eclampsia and time interval between the two deliveries was highly significant, and for women with no previous pre-eclampsia the risk of pre-eclampsia in second pregnancy increased with increasing time interval (for intervals longer than 15 years the adjusted OR was 2.11, 95% CI : 1.75-2.53). For women with previous pre-eclampsia the risk tended to decrease with increasing time interval between deliveries. CONCLUSIONS: The protective impact of a new father for the second pregnancy challenges the hypothesis of primipaternity, and implies that the increase in pre-eclampsia risk ascribed to new father by others is due to insufficient control for interpregnancy interval.

Adult↗

PubMed2000

Symptoms of anxiety and depression among mothers of pre-school children: effect of chronic strain related to children and child care-taking.

BACKGROUND: Factors that affect maternal mental health were studied when the children were 30 and 50 months old, and changes in the importance of these factors over time were analyzed. A specific aim was to elucidate the role of chronic strain related to children and child care-taking. This study follows up previous work on the influence of social class, strain and social support on maternal mental distress when the children were 18 months old. METHODS: The sample is population based, and 1,081 parents were invited to fill out questionnaires. Maternal mental distress was measured by the Hopkins Symptom Checklist (SCL-25). Multiple regression analyses were conducted at each time point and chi-square tests were used to analyze the changes between the estimated regression coefficients over time. RESULTS: Chronic strain related to children and child care-taking consistently predicted maternal mental distress. Among the specific child related strains, problems with child care-taking were significantly associated with maternal symptom levels at all time points. The importance of two specific child problem behaviors (activity level and the child being a worrier) on maternal mental health changed over time. LIMITATIONS: Conclusions about causality can not be drawn based on cross-sectional analyses. The self-report measures used here may be biased by the current mood state. CONCLUSIONS: Problems with child care arrangements and combining work and child care-taking are predictive of maternal mental health when the children are 18, 30 and 50 months old. The risk and protective factors found here may have implications for prevention and intervention.

Adult↗

PubMed2000

Exposure stratified case-cohort designs.

A variant of the case-cohort design is proposed for the situation in which a correlate of the exposure (or prognostic factor) of interest is available for all cohort members, and exposure information is to be collected for a case-cohort sample. The cohort is stratified according to the correlate, and the subcohort is selected by stratified random sampling. A number of possible methods for the analysis of such exposure stratified case-cohort samples are presented, some of their statistical properties developed, and approximate relative efficiency and optimal allocation to the strata discussed. The methods are compared to each other, and to randomly sampled case-cohort studies, in a limited computer simulation study. We found that all of the proposed analysis methods performed well and were more efficient than a randomly sampled case-cohort study.

Biometry↗

PubMed1999

Interior surface materials in the home and the development of bronchial obstruction in young children in Oslo, Norway.

OBJECTIVES: This study assessed the role of polyvinyl chloride (PVC) plastics and textile materials in the home in the development of bronchial obstruction during the first 2 years of life. METHODS: The study was a matched pair case-control study based on a cohort of 3754 newborns in Oslo in 1992 and 1993 who were followed up for 2 years. The case group consisted of 251 children with bronchial obstruction; the control group was matched one-to-one for date of birth. RESULTS: In conditional logistic regression analysis, the risk of bronchial obstruction was related to the presence of PVC flooring (adjusted odds ratio [OR] = 1.89; 95% confidence interval [CI] = 1.14, 3.14) and textile wall materials (adjusted OR = 1.58; 95% CI = 0.98, 2.54). The reference category was wood or parquet flooring and painted walls and ceiling. Further analysis revealed an exposure-response relationship between the assessed amount of PVC and other plasticizer-containing surface materials and the risk of bronchial obstruction. CONCLUSIONS: This study provides new evidence of the role of PVC and textile wall materials in the development of bronchial obstruction in young children.

Bronchial Diseases↗

PubMed1998

The estimated impact of the CCR-5 delta32 gene deletion on HIV disease progression varies with study design. Oslo HIV Cohort Study Group.

OBJECTIVES: To study the impact of the genotype CCR-5 wild-type +/A32 on the progression rate to AIDS and death, and to discuss sources of bias according to study design. METHODS: A prospective study of 310 HIV-positive subjects with follow-up time from study entry (prevalent cohort), and a prospective study of 105 HIV-positive subjects with well-defined time of HIV seroconversion, with follow-up time from the retrospectively assessed date of HIV seroconversion (retrospective incident cohort). RESULTS: Slower progression to AIDS among subjects with CCR-5 +/delta32 than those with CCR-5 +/+ genotype was estimated in the prevalent cohort (P=0.07, log-rank test). Slower progression to death from any cause was also estimated for subjects with CCR-5 +/delta32 (P < 0.05, log-rank test). No differences in survival after AIDS diagnosis were seen (P=0.89, log-rank test). No differences in the progression rate to AIDS (P=0.82, log-rank test) or death (P=0.78, log-rank test) were estimated in the retrospective incident cohort. CONCLUSIONS: The varying estimates of the impact of CCR-5 genotype on progression to AIDS in this and other studies, may be real and reflect differences in the dependence of HIV on the CCR-5 receptor, or may be due to systematic errors caused by study design. Several methodological difficulties occur when the factor studied, such as CCR-5 genotype, is associated both with the risk of being HIV-infected and the progression of disease.

Acquired Immunodeficiency Syndrome↗

PubMed1998

Birth weight and mortality in childhood in Norway.

In order to estimate the association between intrauterine growth and childhood survival, data on birth weight and gestational age from the Norwegian Birth Registry, for all children who survived the first year of life and who were born during the period 1967-1989 were linked to the National Cause of Death Registry for the period 1968-1991. Deaths were categorized into five cause of death groups: malformations, cancer, infections, accidents, and other causes. The adjusted relative risk of death from all causes at ages 1-5 years was 2.18 (95% confidence interval (CI) 1.85-2.56) for children with birth weight <2,500 g as opposed to children with birth weight > or = 2,500 g. For ages 6-10 years, the corresponding adjusted relative risk (95% CI) was 1.83 (1.35-2.48), and for ages 11-15 years, it was 1.35 (0.91-1.99). Death from infections, accidents, and other causes showed a reversed J-shaped association with birth weight, while malformations showed a log-linear decrease in mortality with increasing birth weight. For cancer deaths, low birth weight showed an opposite association. The association between birth weight and childhood mortality is complex, and cause-specific analyses are necessary to understand the connection between intrauterine influences and later mortality.

Accidents↗

PubMed1998

Exposure to nitrogen dioxide and the occurrence of bronchial obstruction in children below 2 years.

BACKGROUND: The objective of the investigation was to test the hypothesis that exposure to nitrogen dioxide (NO2) has a causal influence on the occurrence of bronchial obstruction in children below 2 years of age. METHODS: A nested case-control study with 153 one-to-one matched pairs was conducted within a cohort of 3754 children born in Oslo in 1992/93. Cases were children who developed > or = 2 episodes of bronchial obstruction or one episode lasting >4 weeks. Controls were matched for date of birth. Exposure measurements were performed in the same 14-day period within matched pairs. The NO2 exposure was measured with personal samplers carried close to each child and by stationary samplers outdoors and indoors. RESULTS: Few children (4.6%) were exposed to levels of NO2 > or = 30 microg/m3 (average concentration during a 14-day period). In the 153 matched pairs, the mean level of NO2 was 15.65 microg/m3 (+/-0.60, SE) among cases and 15.37 (+/-0.54) among controls (paired t = 0.38, P = 0.71). CONCLUSIONS: The results suggest that NO2 exposure at levels observed in this study has no detectable effect on the risk of developing bronchial obstruction in children below 2 years of age.

Air Pollution, Indoor↗

PubMed1997

Frequency of sexual partner change in a Norwegian population. Data distribution and covariates.

The number of new sexual partners per year (partner frequency) is a key factor in the spread of sexually transmitted diseases. Data from two Norwegian population-based surveys conducted in 1987 and 1992 were used to estimate recent (in the previous 3 years) and earlier partner frequency and to examine covariates affecting the distribution of partner frequency. Seventy-two percent of respondents reported having no new partners per year, and 2% reported having more than three new partners per year. Results from a Poisson regression model indicated that a low partner frequency was associated with being married or cohabiting, being female, greater age, and late sexual debut. Partner frequency was lower in 1992 than in 1987 (rate ratio = 0.8, 95% confidence interval 0.7-0.9). In comparison with earlier life, there was a large reduction in partner frequency for married/cohabiting individuals. In contrast, there was either no change or some increase in partner frequency for single persons.

Adolescent↗

PubMed1997

No evidence for effects of family environment on asthma. A retrospective study of Norwegian twins.

The risk of developing asthma contingent upon the co-twins' history of asthma was analyzed in a population-based study of 5,864 Norwegian twins. A primary aim was to assess the significance of shared environment for the development of asthma from infancy through age 25. Retrospective reports were collected when the twins were 18 to 25 yr of age. The risk of developing asthma, contingent upon the co-twin's history of asthma, was estimated using survival analyses, and genetic and environmental sources of variation in liability for asthma were analyzed with structural equation models. The cumulative incidence of asthma was 6% for males and 5.4% for females. The relative risk of developing asthma among twins whose co-twin had a positive history of asthma compared with those whose co-twin had no history of asthma was 17.9 (95% CI, 10.3 to 31.0) for identical, and 2.3 (95% CI, 1.2 to 4.4) for fraternal twins. Although shared environment encompasses many of the exposures that are putative risk factors for asthma in this age range, there is no evidence of shared environmental influences for asthma. Rather, 75% of the variation in liability for asthma was explained by genetic effects and the remaining variation was due to nonshared environmental influences. These results suggest that the familial risk for asthma is primarily, genetic.

Actuarial Analysis↗

PubMed1995

Cohort study of the relationship between air pollution and short term health effects as determined by peak expiratory flow measurements.

The aim of the study was to establish if air pollution has short term effects on health and well-being for individuals living in an industrialized area of Norway. A cohort study was designed so that two groups (one randomly selected from the general population and one with preexisting lung disease) were followed hour by hour during two months in the winter and in the summer of 1988. In order to minimize the problems of confounding factors, each individual served as her/his own control. Each participant described through the use of a diary the presence of symptoms from the upper and lower respiratory tract as well as general symptoms of ill health. Measurements of lung function by the use of peak expiratory flow meters were done four times a day. In addition, every second week the participants were subjected t a full spirometric test. Samples of urine and blood were examined, and bacteriological test from the throat was performed at the beginning and at the end of the study. A comprehensive measurement program of outdoor air contaminants (including nitrogen oxides, sulphur dioxide) is presented. Estimation of each participant's exposure was performed hour by hour based on detailed modelling of the measured levels, known emissions of pollutants and meteorological conditions, as well as diary information on the participant's movements through the various micro-environments. The estimated exposures were generally low. In this presentation, a linear regression model and their corresponding parameter estimates were applied on an individual basis to evaluate any effect of air contamination on lung function.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1994

[The extent of HIV testing in the Norwegian population seen in relation to sex behavior].

To estimate the incidence of clinical HIV-testing and the association between testing and sexual habits, data from a 1992 population-based, anonymous survey of sexual behaviour were analysed. The sample size was 10,000 subjects between 18 and 60 years of age and the response rate was 48%. 15% of the males and 13% of the females reported having been HIV-tested at least once during the period 1985-92, and 1% of the sample four times or more. The incidence of testing has increased. However, a decrease in first time testing was observed after 1990. The best predictors of HIV-testing are the partner's test behaviour and the number of sexual partners during a lifetime.

AIDS Serodiagnosis↗

PubMed1994

Interval censoring in longitudinal data of respiratory symptoms in aluminium potroom workers: a comparison of methods.

In a longitudinal study of workers in seven Norwegian aluminium plants, the time to development of asthmatic symptoms could only be determined to lie in the interval between two consecutive health examinations. In a previous paper we analysed the data by survival techniques for interval censored data. In the present paper the data are reanalysed in two ways and compared to the previous analyses. First, it is assumed that occurrence of symptoms coincided with reporting, in which case the data can be analysed as right censored. Secondly, the follow-up times are completely disregarded and the effects of covariates are analysed on the binary outcomes of symptoms. Comparing the estimated effects of the covariates between the three approaches, only minor differences were found. However, the estimates on incidence were strongly influenced by whether the data were analysed as right or interval censored.

Adult↗