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Biomedical subjects

C W Looman

Publications and source records attributed to C W Looman.

At least 19 recordsLinked to original sources
PubMed1998

Menstrual cycle length preceding menopause in relation to age at menopause.

OBJECTIVES: In one of the earlier hypotheses of the etiology of breast cancer (Korenman's 'oestrogen window' hypothesis (1981)), it was assumed that women with a later age at menopause have a longer period with irregular cycles preceding menopause than women with an early menopause. This assumption was tested in a prospective study. METHODS: Subjects were 628 women, born between 1932 and 1941, who had participated in a breast cancer screening project in Utrecht, The Netherlands (the DOM-project) in 1982-1985, and who were still menstruating at that time. The women had filled out a questionnaire and a menstrual calendar every 2 years to determine their age at menopause prospectively. The women had not used oral contraceptives or medicines for menopausal complaints and had reached natural menopause by 1992. The median of the mean menstrual cycle length per woman and the median of the standard deviation of the mean menstrual cycle length per woman were plotted against number of years prior to menopause in three categories of age at menopause (44-49; 50-54; 55-59). RESULTS: During the 9 years prior to menopause, women with a late age at menopause have a somewhat higher mean menstrual cycle length than women with a younger age at menopause (P = 0.0008). Cycle length variability in the 9 years prior to menopause is not statistically significantly different between the three categories of age at menopause (P = 0.16). CONCLUSIONS: The assumption that women with a late age at menopause have a longer period with irregular cycles than women with an earlier age at menopause was not corroborated by our results.

Adult↗
PubMed1998

Crossover or parallel design in infertility trials? The discussion continues.

OBJECTIVE: To determine whether a crossover design results in a different estimate of treatment effect compared with a parallel design. DESIGN: With the aid of a computer program, data sets of subfertile patients were simulated under different assumptions. These patients were subjected to 2 treatments that were compared in either a parallel-design or a crossover-design trial. Results were analyzed using logistic regression. SETTING: University hospital. PATIENT(S): Simulated patients of a heterogeneous subfertile population. INTERVENTION(S): Two treatment modalities with a pregnancy rate of 10% and of 20% in the first cycle were offered for 6 cycles to simulated heterogeneous populations. MAIN OUTCOME MEASURE(S): After 1,000 simulations for each assumption, median pregnancy rates and odds ratios were compared between the crossover- and parallel-design trials. RESULT(S): No relevant difference in estimated treatment effect was found between the designs. The crossover design resulted in more pregnancies overall than the parallel design. CONCLUSION(S): In infertility research, parallel and crossover designs will lead to about the same results. Although the crossover design showed a slight tendency to overestimate the treatment effect of the most effective treatment, this overestimation is clinically not relevant and is small in relation to the random error. Because of its practical advantages and because more pregnancies are achieved, a crossover design should be the first choice in infertility research.

Computer Simulation↗
PubMed1998

Controlled ovarian hyperstimulation and intrauterine insemination for treating male subfertility: a controlled study.

In this randomized crossover trial we investigated whether the use of controlled ovarian hyperstimulation with low-dose human menopausal gonadotrophin in couples with male subfertility leads to a higher probability of conception when intrauterine insemination (IUI) is applied. We also investigated whether the efficacy of IUI in natural or stimulated cycles was related to the severity of male subfertility. Seventy-four couples completed 308 treatment cycles. Thirteen pregnancies occurred after IUI in a natural cycle (pregnancy rate per completed cycle: 8.4%) and 21 after IUI in a stimulated cycle (pregnancy rate per completed cycle: 13.7%). The difference between the two treatment modalities was not statistically significant. The efficacy of IUI in stimulated cycles was related to the severity of the semen defect. In couples with a total motile sperm count < 10 x 10(6), ovarian stimulation did not improve treatment outcome, while it did in couples with a total motile sperm count > or = 10 x 10(6). Compared with the expected chance of conceiving spontaneously without treatment, both natural and stimulated cycles improved the probability of conception. We conclude that, for the group as a whole, ovarian stimulation did not improve the probability of conception. However, in couples with less severe semen defects, ovarian stimulation did improve the probability of conception.

Adult↗
PubMed1998

Does childhood socioeconomic status influence adult health through behavioural factors?

BACKGROUND: The purpose of this study is to assess to what extent the effect of childhood socioeconomic status on adult health could be explained by a higher prevalence of unhealthy behaviour among those with lower childhood socioeconomic status. METHODS: Data were obtained from the baseline of a prospective cohort study in the Netherlands (13 854 respondents, aged between 25 and 74). Childhood socioeconomic group was indicated by occupation of the father, and adult health was indicated by perceived general health, health complaints and mortality. Adult socioeconomic status was measured by current occupation. Behavioural factors were smoking, alcohol consumption, Body Mass Index and physical activity. Relations were analysed using logistic regression models. RESULTS: A clear association between childhood socioeconomic circumstances and adult health was shown, as well as an association between childhood socioeconomic circumstances and health-related behaviour, even after adjustment for current socioeconomic status. Physical activity shows the strongest relation with childhood socioeconomic circumstances. Behavioural factors explain the relation between childhood socioeconomic status and adult health for approximately 10%. CONCLUSIONS: Childhood socioeconomic circumstances have an independent effect on adult health and health-related behaviour: the risk of health problems and health damaging behaviour is higher in lower childhood socioeconomic groups. The independent effect of childhood circumstances on adult health operates for a small part through unhealthy behaviour.

Adolescent↗
PubMed1998

Role of childhood health in the explanation of socioeconomic inequalities in early adult health.

STUDY OBJECTIVE: To examine the contribution of childhood health to the explanation of socioeconomic inequalities in health in early adult life. DESIGN: Retrospective data were used, which were obtained from a postal survey in the baseline of a prospective cohort study (the Longitudinal Study on Socio-Economic Health Differences in the Netherlands). Adult socioeconomic status was indicated by educational level, while health was indicated by perceived general health. Childhood health was measured by self reported periods of severe disease in childhood. Relations were analysed using logistic regression models. The reduction in odds ratios of "less than good" perceived general health for different educational groups after adjustment for childhood health was used to estimate the contribution of childhood health. SETTING: The population of the city of Eindhoven and surroundings in the south east of the Netherlands in 1991. PARTICIPANTS: 2511 respondents, aged 25-34 years, men and women, of Dutch nationality, were included in the analysis. MAIN RESULTS: There was a clear association between childhood health and adult health, as well as an association between childhood health and adult socioeconomic status. Approximately 5% to 10% of the increased risk of the lower socioeconomic groups of having a "less than good" perceived general health can be explained by childhood health. CONCLUSIONS: Childhood health contributes to the explanation of socioeconomic inequalities in early adult health. Although this contribution is not very large, it cannot be ignored and has to be interpreted largely in terms of selection on health.

Adolescent↗
PubMed1997

Regression analysis of recent changes in cardiovascular morbidity and mortality in The Netherlands.

OBJECTIVES: To test whether recent declines in mortality from coronary heart disease were associated with increased mortality from other cardiovascular diseases. DESIGN: Poisson regression analysis of national data on causes of death and hospital discharges. SETTING AND SUBJECTS: Population of the Netherlands, 1969-93. MAIN OUTCOME MEASURES: Annual changes in mortality from coronary heart disease, stroke, and other cardiovascular diseases and annual changes in hospital discharge rates for acute coronary events, stroke, and congestive heart failures. RESULTS: Patterns of cardiovascular mortality changed abruptly in 1987-93. Annual decline in mortality from coronary heart disease increased sharply for women and men: from -1.9% (95% confidence interval -2.2% to -1.6%) and -1.7% (-1.9% to -1.4%) respectively in 1979-86 to -3.1% (-3.5% to -2.6%) and -4.2% (-4.6% to -3.9%) in 1987-93. The longstanding decline in mortality from stroke levelled off: from annual change of -3.3% (-3.7% to -2.8%) and -3.2% (-3.7% to -2.8%) in 1979-86 to -0.1% (-0.7% to 0.4%) and -1.1% (-1.7% to -0.5%) in 1987-93. Mortality from other cardiovascular diseases, however, started to increase: from -2.0% (-2.4% to -1.6%) and -0.2% (-0.5% to 0.2%) in 1979-86 to 1.5% (1.0% to 2.0%) and 1.9% (1.5% to 2.3%) in 1987-93. Hospital discharge rates for acute coronary heart disease, congestive heart failure, and stroke increased during 1980-6. During 1987-93 discharge rates for stroke and coronary heart disease stabilised but rates for congestive heart failure increased. CONCLUSION: Improved management of coronary heart disease seems to have reduced mortality, but some of the gains are lost to deaths from stroke and other cardiovascular diseases. The increasing numbers of patients with coronary heart disease who survive will increase demands on health services for long term care.

Cardiovascular Diseases↗
PubMed1997

Cause-specific mortality trends in The Netherlands, 1875-1992: a formal analysis of the epidemiologic transition.

BACKGROUND: The objective of this study is to produce a detailed yet robust description of the epidemiologic transition in The Netherlands. METHODS: National mortality data on sex, age, cause of death and calendar year (1875-1992) were extracted from official publications. For the entire period, 27 causes of death could be distinguished, while 65 causes (nested within the 27) could be studied from 1901 onwards. Cluster analysis was used to determine groups of causes of death with similar trend curves over a period of time with respect to age- and sex-standardized mortality rates. RESULTS: With respect to the 27 causes, three important clusters were found: (1) infectious diseases which declined rapidly in the late 19th century (e.g. typhoid fever), (2) infectious diseases which showed a less precipitous decline (e.g. respiratory tuberculosis), and (3) non-infectious diseases which showed an increasing trend during most of the period 1875-1992 (e.g. cancer). The 65 causes provided more detail. Seven important clusters were found: four consisted mainly of infectious diseases, including a new cluster that declined rapidly after the Second World War (WW2) (e.g. acute bronchitis/influenza) and a new cluster showing an increasing trend in the 1920s and 1930s before declining in the years thereafter (e.g. appendicitis). Three clusters mainly contained non-infectious diseases, including a new one that declined from 1900 onwards (e.g. cancer of the stomach) and a new one that increased until WW2 but declined thereafter (e.g. chronic rheumatic heart disease). CONCLUSIONS: The results suggest that the conventional interpretation of the epidemiologic transition, which assumes a uniform decline of infectious diseases and a uniform increase of non-infectious diseases, needs to be modified.

Adolescent↗
PubMed1996

Age-dependent decrease in embryo implantation rate after in vitro fertilization.

OBJECTIVE: To investigate the relation between the implantation rate per embryo after replacement in IVF-ET in relation to female age. DESIGN: Retrospective study using linear and biphasic models in a multivariate analysis. SETTING: Academic tertiary care institution. INTERVENTION(S): In vitro fertilization-ET and determination of gestational sacs at 6 to 7 weeks of pregnancy buy ultrasound. MAIN OUTCOME MEASURE(S): Implantation rate as defined by the number of gestational sacs per embryo replaced. RESULT(S): Woman's age and embryo morphology were strongly related to the implantation rate, indication for IVF-ET and cycle rank number also were related significantly but less strongly. A linear model was built describing the decrease in implantation rate with age, resulting in a decrease of approximately 7%. A biphasic model was tested also and performed significantly better, resulting in a yearly decrease of > 20% after 37 years of age. CONCLUSION(S): The most important independent factors related to the ability of embryos to implant are female age and embryo morphology. The best way to describe the relation with female age is biphasic model with a discontinuity at approximately 37 years of age.

Aging↗
PubMed1996

Differences in the misreporting of chronic conditions, by level of education: the effect on inequalities in prevalence rates.

OBJECTIVES: Many studies of socio-economic inequalities in the prevalence of chronic conditions rely on self-reports. For chronic nonspecific lung disease, heart disease, and diabetes mellitus, we studied the effects of misreporting on variations in prevalence rates by respondents' level of education. METHODS: In 1991, a health interview survey was conducted in the southeastern Netherlands with 2867 respondents. Respondents' answers were compared with validated diagnostic questionnaires in the same survey and the diagnoses given by the respondents' general practitioners. RESULTS: Misreporting of chronic lung disease, heart disease, and diabetes may be extensive. Depending on the condition and the reference data used, the confirmation fractions ranged between .61 and .96 and the detection fractions between .13 and .93. Misreporting varied by level of education, and although various patterns were observed, the dominant pattern was that of more underreporting among less educated persons. The effects on prevalence rates were to underestimate differences by level of education to a sometimes considerable degree. CONCLUSIONS: Misreporting of chronic conditions differs by respondents' level of education. Health interview survey data underestimate socioeconomic inequalities in the prevalence of chronic conditions.

Adolescent↗
PubMed1995

Withdrawal or withholding of treatment at the end of life. Results of a nationwide study.

BACKGROUND: Decisions to withhold or withdraw treatment (nontreatment decisions) become increasingly important because they have to be made more frequently and more explicitly. This nationwide study provides information on the occurrence and background of these nontreatment decisions. METHODS: Three studies were undertaken: interviews with 405 physicians, 5197 answered questionnaires concerning deceased persons, and information about 2257 deaths collected by a prospective study. RESULTS: Of all deaths, 30% appeared to be sudden and unexpected. In 39% of all nonsudden deaths, a nontreatment decision was made. This percentage varied by specialty (28% to 55%). Nontreatment decisions were made more often in older female patients. The decisions were made at the explicit request of the patient (19%), after discussion with the patient or after a previous wish (22%), or without any involvement of the patient (59%). Of this last group, 87% of patients were not competent at the time of the decision. In 24% of cases of nontreatment, life was shortened by at least a week. Of all physicians interviewed, 56% had changed their attitude since the beginning of their practice, most of them toward more nontreatment decisions at the end of life. CONCLUSIONS: Nontreatment decisions are made frequently in medical practice. Most often the physician has to weigh medical and nonmedical burdens and benefits. For this to be done properly, the patient should be involved whenever possible. Other requirements are optimal palliative treatment, better prognostic knowledge, consultation of other specialists, and the absence of defensive motives.

Adolescent↗
PubMed1995

Diverging trends in colorectal cancer morbidity and mortality. Earlier diagnosis comes at a price.

In developed countries, time trends in the incidence of colorectal cancer differ markedly from trends in mortality. This study sought to explain simultaneously changes in both colorectal cancer incidence and mortality. Data on first admissions, interventions and outcome from the national hospital registry over the period 1978-1989 and data on mortality from Statistics Netherlands over the same period were analysed by age-period models and subsequently entered in a Markov chain model, simulating disease history from first admission to death. Over the period 1978-1989, age adjusted numbers of first admissions and interventions increased by 37% and 32%, respectively, while mortality declined by 8%. For every 100 patients admitted between 1987 and 1989, 13 more will survive compared with 1978-1980. Of these, 3 will be saved by improving results of primary treatment but the other 10 will survive their diagnosis for the subsequent 10 years. Although progress in treatment has been made, therapeutic improvement can account only for the smaller part of the divergence between morbidity and mortality. Increased diagnostic activity, raising incidence and lowering mortality simultaneously, is the most likely cause of the unexplained divergence.

Adult↗
PubMed1994

The prediction of the chance to conceive in subfertile couples.

OBJECTIVE: To develop a model that can predict the chance to conceive spontaneously in subfertile couples. DESIGN: In a cohort study, a consecutive series of patients consulting infertility was followed up. We related information from previous history, physical examination, postcoital tests (PCT), semen analyses, and sperm penetration meter tests with the occurrence of a spontaneous pregnancy. SETTING: Fertility center in a university hospital. PATIENTS: Nine hundred ninety-six couples consulting for infertility due to cervical hostility, male subfertility, or unexplained infertility. INTERVENTIONS: None. MAIN OUTCOME MEASURE(S): Time between intake and occurrence of the first spontaneous pregnancy. RESULTS: Information from the previous history (duration of infertility, primary or secondary female infertility, age of the woman, fertility problems in male's family), the percentage motile sperm in the first semen analysis, and the result of the first PCT are sufficient to predict the chance to conceive. A pocket chart is presented for easy use of the model. CONCLUSIONS: With a limited amount of diagnostic information, the chance to conceive spontaneously can be predicted.

Adult↗
PubMed1994

Moderate drinking: no impact on female fecundity.

OBJECTIVE: To determine the effect of moderate alcohol intake on probability of conception. DESIGN: Prospective cohort study. SETTING: Normal healthy women enrolled in an artificial donor insemination program. PATIENTS: Women starting artificial donor insemination for the very first time were selected. INTERVENTIONS: Alcohol exposure was measured through a self-administered questionnaire at intake of study. MAIN OUTCOME MEASURE: A first positive pregnancy test as indicative for conception. RESULTS: Women with moderate alcohol intake had a slightly higher, though not significant, probability of conception compared with nondrinkers (Hazard Ratio 1.20; 95% confidence interval 0.90 to 1.60). CONCLUSION: Moderate alcohol intake has no negative impact on female fecundity.

Adult↗
PubMed1994

Living standards and mortality in the European Community.

OBJECTIVE: The association between living standards and mortality in the European Community (EC) was investigated using regional level data from all EC member countries. DATA AND METHODS: Data covering the 1980s were extracted from various publications. Data on "all cause" mortality (standardised mortality ratios, both sexes, all ages), living standards (gross domestic product, car access, unemployment rates), and some potential confounders (population density, agricultural employment, industrial employment, country) were available for 133 regions. Multiple regression analysis was used for each living standard variable, taking lnSMR as the dependent variable. RESULTS: It is only after taking into account potential confounders that higher living standards are associated with lower mortality. Unemployment rates have the strongest association--each additional percentage in unemployment in the regional population is associated with an increase in mortality by 0.81%. There is important variation between countries in the living standards--mortality relationship. The latter ranges from relatively strong in the UK to absent in Italy. DISCUSSION: The results of this study show that there is an association between living standards and mortality at the regional level in the EC, but that this association comes to light only after controlling for confounding variables. It seems that the mortality increasing effects of urbanisation and industrialization have obscured the mortality lowering effects of high living standards. In addition, factors specific to countries (such as dietary habits) act as confounders. The latter finding is interpreted in the light of differences between countries in the way in which they have gone through the "epidemiologic translation" from infectious diseases to the "western" diseases that currently dominate the mortality pattern.

Adolescent↗
PubMed1993

Life-terminating acts without explicit request of patient.

In the Dutch nationwide study on medical decisions concerning the end of life (MDEL) life-terminating acts without the explicit request of the patient (LAWER) were noted in 0.8% of all deaths. We present here quantitative information and a discussion of the main issues raised by LAWER. In 59% of LAWER the physician had some information about the patient's wish; in 41% discussion on the decision would no longer have been possible. In LAWER patients tend to be younger and more likely to be male and to have cancer than in non-acute deaths generally. The physician (specialist or general practitioner) knew the patient on average 2.4 years and 7.2 years, respectively. Life was shortened by between some hours and a week at most in 86%. In 83% the decision has been discussed with relatives and in 70% with a colleague. In nearly all cases, according to the physician, the patient was suffering unbearably, there was no chance of improvement, and palliative possibilities were exhausted. MDEL probably will increase in number in future but interviews with Dutch physicians suggest a possible fall in LAWER, even though there will always be some situations in which a well-considered LAWER decision may have to be made.

Adolescent↗
PubMed1993

Outdoor air temperature and mortality in The Netherlands: a time-series analysis.

Death rates become progressively higher when outdoor air temperature rises above or falls below 20-25 degrees C. This study addresses the question of whether this relation is largely attributable to the direct effects of exposure to heat and cold on the human body in general, and on the circulatory system in particular. The association between daily mortality and daily temperatures in the Netherlands in the period 1979-1987 was examined by controlling for influenza incidence, air pollution, and "season"; distinguishing lag periods; examining effect modification by wind speed and relative humidity; and distinguishing causes of death. Important direct effects of exposure to cold and heat on mortality were suggested by the following findings: 1) control for influenza incidence reduced cold-related mortality by only 34% and reduced heat-related mortality by 23% (the role of air pollution and "season" was negligible); 2) 62% of the "unexplained" cold-related mortality, and all heat-related mortality, occurred within 1 week; and 3) effect modification by wind speed was in the expected direction. The finding that 57% of "unexplained" cold-related mortality and 26% of the "unexplained" heat-related mortality was attributable to cardiovascular diseases suggests that direct effects are only in part the result of increased stress on the circulatory system. For heat-related mortality, direct effects on the respiratory system are probably more important. For cold-related mortality, the analysis yielded evidence of an important indirect effect involving increased incidence of influenza and other respiratory infections.

Air Pollution↗