Crossover designs versus parallel studies in infertility research.
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Cross-Over Studies↗
Biomedical subjects
C W Looman
Publications and source records attributed to C W Looman.
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↗
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↗
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↗
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↗
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↗
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↗
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↗
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↗
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↗
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↗
Life-terminating acts without explicit request of patient.
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Decision Making↗
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↗
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↗
Prevalence of smoking in physicians and medical students, and the generation effect in The Netherlands.
This study investigates smoking habits and attitudes towards smoking in general practitioners, consultants at a university hospital, medical students and students of health policy and management (H.P.M.). An anonymous, self-administered postal survey was used. Thirty-eight percent of the general practitioners, 27% of the consultants, 18% of the medical students and 31% of the H.P.M. students are current smokers. The prevalence of smoking was found to be higher in the male general practitioners and the male H.P.M. students than in the general male population. The prevalence of smoking was lower in female physicians and students than in their male counterparts and also lower than in the general female population. Medical students are not inclined to start smoking: a strong generation effect can be observed. This will reinforce the current downward trend in the prevalence of smoking in Dutch physicians. The doctors were found to have a suboptimal level of knowledge about methods of smoking cessation and about the association between smoking and health disorders. Most Dutch physicians, especially those who smoke, fail to perceive their role as an example to the general population concerning smoking behaviour. Medical students were found to have even less recognition of their future exemplary role.
Adolescent↗
Determinants of regional differences in lung cancer mortality in The Netherlands.
Although regional differences in lung cancer mortality are likely to be attributable to regional differences in tobacco smoking, studies in various countries found only weak relationships. This paper aimed at explaining regional differences in lung cancer mortality in the Netherlands. In a first step, clues for the role of smoking were obtained from a detailed description of regional mortality differences. These differences were found to be strongly determined by cohort effects: they vary between birth cohorts, and have been stable for over 30 years. Regional mortality differences reflect a diffusion of the lung cancer epidemic from high-income regions to low-income regions. These findings are suggestive of a relationship with regional differences in trends in cigarette smoking. In a second step, by means of multiple regression analysis, mortality differences in 1980-84 were related to available data on cigarette smoking and two other possible risk factors: work in transport and manufacturing industry, and air contamination. The independent variables referred to the 1970s. Positive associations with various smoking measures were found for women, but for men the associations were weak or non-existent. Mortality differences among men 45-64 years were associated with work in transport and manufacturing industry. Strong associations with air contamination were found for men and women 65 years and older. Additional analysis showed that regional differences in lung cancer among old men were strongly associated with smoking in 1930, i.e. half a century before. Changes in the regional pattern of tobacco consumption between 1930 and 1970 explain why smoking in 1970 is not associated with mortality differences in the 1980s.(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
Air pollution, lagged effects of temperature, and mortality: The Netherlands 1979-87.
OBJECTIVE: To explore whether the apparent low threshold for the mortality effects of air pollution could be the result of confounding. DESIGN: The associations between mortality and sulphur dioxide (SO2) were analysed taking into account potential confounding factors. SETTING: The Netherlands, 1979-87. MEASUREMENTS AND MAIN RESULTS: The number of deaths listed by the day on which the death occurred and by the cause of death were obtained from the Netherlands Central Bureau of Statistics. Mortality from all causes and mortality from four large groups of causes (neoplasms, cardiovascular diseases, respiratory diseases, and external causes) were related to the daily levels of SO2 air pollution and potential confounders (available from various sources) using log-linear regression analysis. Variables considered as potential confounders were: average temperature; difference between maximum and minimum temperatures; amount of precipitation; air humidity; wind speed; influenza incidence; and calendar year, month, and weekday. Both lagged and unlagged effects of the meteorological and influenza variables were considered. Average temperature was represented by two variables--'cold', temperatures below 16.5 degrees C, and 'warm', those above 16.5 degrees C--to allow for the V shaped relation between temperature and mortality. The positive regression coefficient for the univariate effect of SO2 density on mortality from all causes dwindles to close to zero when all potential confounding variables are taken into account. The most important of these represents the lagged (one to five days) effect of low temperatures. Low temperatures have strong lagged effects on mortality, and often precede relatively high SO2 densities in the Netherlands. Results were similar for separate causes of death. While univariate associations suggest an effect of air pollution on mortality in all four cause of death groups, multivariate analyses show these effects, including that on mortality from respiratory diseases, are a result of confounding. CONCLUSIONS: The SO2 density (or that of compounds closely associated with SO2) does not seem to have any short term effect on mortality in the Netherlands. SO2 levels higher than those currently reached in the Netherlands (above 200 micrograms/m3) may have a measurable effect on mortality and this should be investigated. Furthermore, analyses of the public health impact of outdoor air pollution should properly control for the lagged effects of temperature.
Air Pollution↗
Deciding not to resuscitate in Dutch hospitals.
The use of do not resuscitate (DNR) orders in Dutch hospitals was studied as part of a nationwide study on medical decisions concerning the end of life. DNR decisions are made in 6 per cent of all admissions, and 61 per cent of all in-hospital deaths were preceded by a DNR decision. We found that in only 14 per cent of the cases had the patients been involved in the DNR decision (32 per cent of competent patients). The concept of futility is analysed as these findings are discussed. We conclude that determining the effectiveness of resuscitation is a medical judgement whereas determining the proportionality (burden/benefit ratio) of it requires a discussion between doctor and patient (or his or her surrogates). Since the respondents in the cases without patient involvement gave many reasons for their decision that went beyond determining effectiveness, we conclude that more patient involvement would have been desirable.
Death Certificates↗