Biomedical subjects
J Olsen
Publications and source records attributed to J Olsen.
[Randomization and alternatives].
The randomized clinical study is being threatened from many perspectives, and participation in such studies shows a falling tendency. Assurance of the best possible treatment for future patients will be considerably weakened if randomized studies have to be replaced by non-experimental studies. This is because the choice of treatment in itself makes ordinary control of confounders impossible both in design and analysis. The rationale of the randomized study and certain alternative study designs are explained in the article.
Why do short term workers have high mortality?
Increased mortality is often reported among workers in short term employment. This may indicate either a health-related selection process or the presence of different lifestyle or social conditions among short term workers. The authors studied these two aspects of short term employment among 16,404 Danish workers in the reinforced plastics industry who were hired between 1978 and 1985 and were followed to the end of 1988. Preemployment hospitalization histories for 1977-1984 were ascertained and were related to length of employment between 1978 and 1988. Workers who had been hospitalized prior to employment showed a 20% higher risk of early termination of employment than those never hospitalized (rate ratio (RR) = 1.20, 95% confidence interval (CI) 1.16-1.29), and the risk increased with number of hospitalizations. For workers with two or more preemployment hospitalizations related to alcohol abuse or violence, the rate ratios for short term employment were 2.30 (95% CI 1.74-3.06) and 1.86 (95% CI 1.35-2.56), respectively. An unhealthy lifestyle may also be a determinant of short term employment. While it is possible in principle to adjust for lifestyle factors if proper data are collected, the health-related selection of workers requires careful consideration when choosing a reference group for comparative studies of cumulative occupational exposure.
[Birth weight as a predictor of young men's intelligence. A historical cohort study].
The objective was to examine the relation between birth weight and cognitive function in young adult life. The study includes 4300 Danish conscripts born between 1973 and 1975, and the main outcome measure was the mean score in the Børge Prien IQ test at drafting. The score is the number of correct answers to 78 questions and it correlates with full scale intelligence quotient (IQ). Data on birth weight were collected from the birth registry. The mean score in the Børge Prien test increased from 39.9 at a birth weight of < or = 2500 g to 44.6 at a birth weight of 4200 g after adjustment for gestational age and length at birth, maternal age and parity, and other variables. Above a birth weight of 4200 the test score decreased slightly. Birth weight is associated with cognitive performance in young adult life and factors that interference with foetal growth may influence adult cognitive performance.
Oral clefts, transforming growth factor alpha gene variants, and maternal smoking: a population-based case-control study in Denmark, 1991-1994.
Studies in the United States have indicated that maternal first trimester smoking and infant transforming growth factor alpha (TGFA) locus mutations are associated with non-syndromic cleft lip and/or palate (CLP) and that a synergistic effect of these two risk factors occurs. Based on a Danish case-control study of CLP, the authors studied the effects of smoking and TGFA alleles in an ethnically homogeneous setting. Interview information was obtained for mothers of 302 CLP cases (96% of eligible) and for 567 mothers of nonmalformed children (94% of eligible). Multivariate logistic regression analyses revealed that smoking was associated with a moderately increased risk of cleft lip +/- cleft palate (CL(P)) (odds ratio = 1.40, 95% confidence interval 0.99-2.00). No association between smoking and isolated cleft palate (CP) was observed. TGFA genotype was not associated with either CL(P) or CP, and no synergistic effect with smoking was observed. The "rare" TGFA allele occurred in 25% of both cases and controls compared with an average of 14% in other white control groups. Furthermore, the frequency of CLP in Scandinavia is among the highest in the world. Hence, it is possible that the previously reported association between TGFA and CLP to some degree can be attributable to confounding by ethnicity.
Re: Residual confounding.
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[The effect of transdermal nicotine patches in smoking cessation. A randomized trial in pharmacy customers in Denmark].
The aim of the study was to examine the effect of 24-hour nicotine patches in smoking cessation among over-the-counter customers in Denmark based on a randomized, double-blind, placebo-controlled trial. Participants were consecutive customers to whom nicotine patches were offered free of charge and as the only treatment. Forty-two pharmacies in the areas of Aarhus and Copenhagen in Denmark participated in the trial, and 522 customers who smoked 10 or more cigarettes per day were randomized to either nicotine or placebo patches from January to March 1994. Twenty-four-hour patches were offered for a three-month period. Those smoking 20 or more cigarettes per day started on 21 mg/day patches. Customers who smoked less started on 14 mg/day patches and all the participants were gradually reduced to 7 mg/day patches during the study period. Smoking behaviour and compliance were recorded by means of self-administered question-naires and telephone interviews. Smoking status was recorded following each four-week treatment period, and 26 weeks after inclusion. There was a significant increase in smoking cessations rates, but only among smokers who started on 21 mg/day patches after eight weeks of follow-up. No significant differences in smoking cessation rates were seen among smokers who started with the low dose nicotine or placebo patches.
Risk of breast cancer in offspring of male breast-cancer patients.
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gamma-linolenic acid (GLA)-mediated cytotoxicity in human prostate cancer cells.
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Drug use in first pregnancy and lactation: a population-based survey among Danish women. The EUROMAP group.
OBJECTIVE: To examine the drug prescription pattern in Danish women from 12 weeks prior to conception until 12 weeks post-partum. METHOD: A drug utilization study based on The North Jutland Prescription Database. The Danish pharmacies use a computerized accounting system for all subsidized drugs and this was linked to the Danish Medical Birth Registry concerning prescription patterns for all women who had given birth in the county of North Jutland from 1991 to 1996. RESULTS: The analysis included 16,001 primiparous women, who had redeemed 34,834 prescriptions prior to, during and after pregnancy. During pregnancy 44.2% of the women received prescriptions for at least one drug. Users received 2.6 prescriptions on average during pregnancy: 5% of the users redeemed 24.2% of all prescriptions. The proportion of women who redeemed prescriptions for more than three different drugs was 2.7%. The majority of prescriptions were for antibiotics (28.7%), gynaecological drugs (13.3%) and anti-asthma drugs (7.6%). The post-partum prescription proportion was 34.0% and the majority of the prescriptions during this period were for penicillins (20.1%), ophthalmologicals (15.5%) and corticosteroids for dermatological use (5.7%). CONCLUSION: A high proportion of the women received drugs during pregnancy. The pattern of drug use within the Anatomical Therapeutical Chemical (ATC) groups changed, i.e. the amount of broad spectrum antibiotics decreased and the proportion of prescriptions for local use increased. A small proportion of women redeemed prescriptions for more than three different drugs during pregnancy.
Menstrual cycle pattern and fertility: a prospective follow-up study of pregnancy and early embryonal loss in 295 couples who were planning their first pregnancy.
OBJECTIVE: To characterize how the menstrual cycle pattern relates to fertility regardless of potential biases caused by inappropriate coital timing during the menstrual cycle or early embryonal loss. DESIGN: Prospective follow-up study. SETTING: Healthy couples recruited throughout Denmark. PATIENT(S): Two hundred ninety-five couples who were planning their first pregnancy were followed up from the discontinuation of birth control until a pregnancy was recognized within six menstrual cycles. Early embryonal losses were detected by changes in urinary hCG levels. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): The probability of pregnancy occurring within one menstrual cycle (fecundity). RESULT(S): In women who had a cycle length that differed by >10 days from the usual cycle length, fecundity was approximately 25% that of women who had no variation (odds ratio 0.25, 95% confidence interval 0.09-0.68). When the combined effect of cycle variation and cycle length was assessed, cycle variation was a persistent strong predictor of fecundity. CONCLUSION(S): The mechanisms of the present findings probably are female functional disturbances in ovulation, conception, implantation, or sustained pregnancy, linked with variable menstrual cycle length. Thus, identification of medical and environmental causes of abnormal menstrual cycle patterns may provide clues to the causes of infertility. Moreover, the menstrual cycle pattern also should be taken into consideration in the clinical decision-making process.
Distress and reduced fertility: a follow-up study of first-pregnancy planners.
OBJECTIVE: To assess the effect of psychological distress on time to first pregnancy. DESIGN: A follow-up study of time to pregnancy with prospective data on distress, with controlling for potential confounding variables. SETTING: Two university hospitals. PATIENT(S): Danish couples (n = 430) who were planning their first pregnancy and had no previous reproductive experience were followed for six menstrual cycles. Psychological distress was measured in each menstrual cycle by the General Health Questionnaire. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): A clinically recognized pregnancy or a biochemical pregnancy detected in urine samples from each period of vaginal bleeding. RESULT(S): For cycles with the highest distress score (General Health Questionnaire score >80th percentile), the probability of conception per cycle was 12.8%, compared with 16.5% in other cycles (adjusted odds ratio [OR] 0.6; 95% confidence interval [CI] 0.4-1.0). The effect of distress was found almost exclusively among women with long menstrual cycles (OR 0.1; 95% CI 0.01-0.4 and OR 0.9; 95% CI 0.5-1.4 for women with cycles of > or =35 and <35 days, respectively). An increased incidence of early embryonal loss was also found among highly distressed women with long cycles, but was based on a small number of observations. CONCLUSION(S): Psychological distress may be a risk factor for reduced fertility in women with long menstrual cycles.
Induced abortion and subsequent pregnancy duration.
OBJECTIVE: To examine whether induced abortion influences subsequent pregnancy duration. METHODS: Women who had their first pregnancies during 1980, 1981, and 1982 were identified in three Danish national registries. A total of 15,727 women whose pregnancies were terminated by first-trimester induced abortions were compared with 46,026 whose pregnancies were not terminated by induced abortions. All subsequent pregnancies until 1994 were identified by register linkage. RESULTS: Preterm and post-term singleton live births were more frequent in women with one, two, or more previous induced abortions. After adjusting for potential confounders and stratifying by gravidity, the odds ratios of preterm singleton live births in women with one, two, or more previous induced abortions were 1.89 (95% confidence interval [CI] 1.70, 2.11), 2.66 (95% CI 2.09, 3.37), and 2.03 (95% CI 1.29, 3.19), respectively. Odds ratios of post-term singleton live births in women with one, two, or more previous induced abortions were 1.34 (95% CI 1.24, 1.44), 1.50 (95% CI 1.26, 1.78), and 1.58 (95% CI 1.09, 2.28), respectively. CONCLUSION: The study showed an increase in preterm and post-term pregnancies after induced abortions. The risk of post-term delivery was high regardless of the interpregnancy interval, whereas increased risk of preterm delivery was seen mainly when interpregnancy intervals were longer than 12 months.
Prescribing during pregnancy and lactation with reference to the Swedish classification system. A population-based study among Danish women.
AIM: To assess the current prescribing pattern for 15,756 primiparae before, during, and after their pregnancies with reference to fetal and neonatal risk. METHOD: A prescription database study with linkage to The Danish Medical Birth Registry from 1991 to 1996. The drug subsidy system in Danish retail pharmacies, made it possible to identify prescriptions by individual use. All 34,334 prescriptions were set against the Swedish classification of risk of drug use in pregnancy and lactation. RESULTS: During pregnancy, safe (group A), potentially harmful (group B3, C, and D), and non-classifiable drugs accounted for 40.9%, 26.6% and 28.7% respectively. The proportion of women who redeemed drugs was 29.2%, 8.6%, 18.7% and 0.9% from drug groups A, B, C and D respectively. The proportion of prescriptions from high risk groups declined during the course of pregnancy. Postpartum, safe drugs (group I and II), drugs with possible harmful neonatal effects (group III), and non-classifiable drugs accounted for 43.5%, 4.8%, and 35.8% of the prescriptions, respectively. CONCLUSION: According to the Swedish classification system, we found that during pregnancy and lactation a high proportion of Danish women were exposed to one or more drugs in high risk groups; furthermore, knowledge regarding their safety for the fetus and neonate was limited for a large proportion of the prescriptions. Current evidence about long-term effects of prenatal exposure stresses the need for long-term follow-up of health and development among exposed children.
Low use of long-term hormone replacement therapy in Denmark.
AIMS: To examine individual use of hormone replacement therapy (HRT) in a defined population of Danish women during a 5-year period. HRT may reduce osteoporosis and cardiovascular disease in postmenopausal women, but may also have side-effects. Little is known about the use of HRT in most populations. METHODS: A Pharmacoepidemiological Prescription Database was used to identify all reimbursed prescriptions for HRT in the county during the period 1991 to 1995. The Danish retail pharmacies' drug subsidy system made it possible to identify prescriptions by individual use. RESULTS: We examined 255797 HRT prescriptions issued during the period in the County of North Jutland. Total sales reached 16.5 million defined daily doses (DDDs), purchased by 31653 women, which corresponds to 26.9% of the female population above the age of 39 years. The annual prevalence proportion of current users rose from 10.4% to 14.8% during the study period, and the therapeutic intensity (DDD/1000 women/day) increased from 20.6 to 32.0. The mean DDD sum of systemic HRT per user was 73.4 in 1991; it and the proportion of users who received less than 90 DDD per year (83.4% in 1991) remained almost constant during the study period. The amount of oestrogen unopposed by progestin was high, 28.1% of all prescriptions. CONCLUSIONS: Less than one-fifth of the study population used HRT for more than 3 months per year, and only 32.8% of the women who were new users of HRT in 1992 continued this therapy throughout the study period.
Risk of malformations and other outcomes in children exposed to fluconazole in utero.
AIM: Fluconazole is an active drug systematically used in the oral treatment of vaginal candidiasis and other fungal diseases. We examined the risk of malformations and other birth outcomes following pregnancy related exposures. METHOD: From 1 January 1991 to 31 December 1996 we identified 165 women who had taken fluconazole just before or during pregnancy in the Pregnancy Outcome Section of the North Jutland Pharmacoepidemiological Prescription Database, Denmark, which is linked to the Danish Medical Birth Registry. We compared their birth outcomes (malformation, low birth weight and preterm delivery) with the outcomes among 13 327 women who did not receive any prescriptions during their pregnancies. RESULTS: The prevalence of malformation was 3.3% (four cases) among the 121 women, who had used fluconazole in the first trimester, and 5.2% (697 cases) in offspring to controls (odds ratio: 0.65, 95% confidence limits: 0.24-1.77). Furthermore, we did not find any significantly elevated risk of preterm delivery (odds ratio: 1.17, 95% confidence limits: 0.63-2.17) and low birth weight (odds ratio: 1.19, 95% confidence limits: 0.37-3.79). CONCLUSION: The study showed no increased risk of congenital malformations, low birth weight or preterm birth in offspring to women who had used single dose fluconazole before conception or during pregnancy.
Fetal growth and adverse birth outcomes in women receiving prescriptions for acetaminophen during pregnancy. EuroMap Study Group.
We studied the association between acetaminophen exposure during pregnancy and the prevalence of congenital abnormalities and fetal growth. Our study included 123 women who had received a prescription of acetaminophen during pregnancy and/or 30 days before conception and 13,329 controls who did not receive any prescription at all. We found more malformations among those who received a prescription with an odds ratio of 2.3 (95% CI 1.0-5.4), but the type of malformations did not indicate a causal link. When restricting the study to first time pregnancies, we identified 58 women who received a prescription of acetaminophen during pregnancy and 30 days before conception and 7472 controls. We found no excess risk of malformation [OR = 0.7 (95% CI 0.1-5.5)], and no evidence that acetaminophen should influence fetal growth.