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At least 19 recordsLinked to original sources

Colon cancer controls versus population controls in case-control studies of occupational risk factors.

BACKGROUND: Since updated population registers do not exist in many countries it is often difficult to sample valid population controls from the study base to a case-control study. Use of patient controls is an alternative option if the exposure experience under study for these patients are interchangeable with the experience for population controls. Patient controls may even be preferable from population controls under certain conditions. In this study we examine if colon cancer patients can serve as surrogates for proper population controls in case-control studies of occupational risk factors. METHODS: The study was conducted from 1995 to 1997. Incident colon cancer controls (N = 428) aged 35-69 years with a histological verified diagnosis and population controls (N = 583) were selected. Altogether 254 (59%) of the colon cancer controls and 320 (55%) of the population controls were interviewed about occupational, medical and life style conditions. RESULTS: No statistical significant difference for educational level, medical history or smoking status was seen between the two control groups. There was evidence of a higher alcohol intake, less frequent work as a farmer and less exposure to pesticides among colon cancer controls. CONCLUSIONS: Use of colon cancer controls may provide valid exposure estimates in studies of many occupational risk factors for cancer, but not for studies on exposure related to farming.

Adult↗

[Implantable devices for permanent venous access. A single-center prospective study comparing an AIDS population with a control population (80 cases)].

Although the tolerance of indwelling catheters in AIDS patients has been evaluated, the complications of implanted devices in this population are unknown. This encouraged us to compare in a prospective unicenter trial, dealing with 80 consecutive implanted devices, the complications of this kind of system in 20 AIDS patients, versus a control population. The follow-up was 10,658 days. No patient was excluded or lost to follow-up. In the control population, the infection rate was 5% (0.036 per 100 catheter days). We observed 3 thromboses (5%). In the AIDS group, the infection rate was 25% (0.21 per 100 catheter days). We observed 1 thrombosis (5%). This trial shows that implanted devices are more frequently infected in AIDS patients (p less than 0.05) than in a control population; it suggests that the infection rate in AIDS patients is not superior to the indwelling catheter rate, as reported in the literature. The precision of bacteriological tests and use of antibiotic therapy adapted to the clinical context should help to determine, in the presence of suspected infection, whether the implanted device can be maintained or should be removed in this high risk population.

Acquired Immunodeficiency Syndrome↗

Population control II: The population establishment today.

Although population assistance represents a relatively small share of official development assistance, it influences many other aspects of development planning. The organizations that comprise the population establishment have a common purpose--the reduction of population growth in the Third World--but they are not homogeneous and sometimes have conflicting goals and strategies. National governments, multilateral agencies, nongovernmental organizations, foundations, academic centers, and pressure groups all contribute to creating and sustaining what has become a virtual population control industry. Through scholarships, travel grants, awards, and favorable publicity, Third World elites have been encouraged to join the population establishment. The World Bank, the U.S. Agency for International Development, and the U.N. Fund for Population Activities have pursued explicit strategies for pressuring Third World governments to design and implement population policies, most recently in Africa.

Coercion↗

Chronic gastric ulcer and stress. A comparison of an ulcer population with a control population regarding stressful events over a lifetime.

Stress was measured by the frequency of 31 major life events with consequent change and distress scores in 50 patients with chronic gastric ulcer and 50 control subjects, matched for age, sex and place of residence. The gastric ulcer population did not differ from the control population regarding the number of events experienced and the associated change and distress scores. However, when analysed according to social grade, the ulcer patients in the lower status suburbs experienced more events and more change than their controls, but the stress scores were similar. In the higher status suburbs, no difference was present between the patients and controls. Change and distress scores rose progressively with age, but there was no significant difference in the number of events experienced between the three age groups. Both men patients and their controls experienced significantly more events and higher change scores than women patients and their controls.

Adult↗

The feasibility of a control population for a randomized control trial of seizure prophylaxis in the hypertensive disorders of pregnancy.

OBJECTIVE: To document the feasibility of a control population for a randomized controlled trial, we report our experience in managing hypertensive pregnancies without seizure prophylaxis. STUDY DESIGN: An 8-year cross-sectional study in one institution was performed of all hypertensive patients. RESULTS: Of 467 patients with preeclampsia or superimposed preeclampsia managed without seizure prophylaxis, 18 had seizure activity, 3.9% (95% confidence interval 2.3% to 6.0%). There was no seizure-related maternal mortality or major morbidity, and the perinatal mortality rate after 28 gestational weeks was the same in patients with or without seizures. By logistic regression seizures were 17.4 times more likely in preeclampsia and 8.1 times more likely in chronic hypertension with superimposed preeclampsia, compared with gestational or chronic hypertension alone. CONCLUSION: The rate of seizures in patients with preeclampsia or superimposed preeclampsia managed without seizure prophylaxis was low and unassociated with an increase in maternal or perinatal mortality. A control arm is feasible in a randomized, controlled trial to address the issue of whether antiseizure medication can prevent eclampsia.

Anticonvulsants↗

[Placental infection in Rwanda: comparison an HIV infected population and a control population].

We report an histological study from term placentas of 286 HIV positive women born in Rwanda. We observed chorioamnionitis without any pathogen in 15% of the cases, cocci Gram positive infection in 12 observations and malaria infection in 75% of placentas. We noted 71 cases of active malaria infection with Plasmodium falciparum trophozoites in the erythrocytes of the intervillous spaces, and 135 cases of chronic infection with malaria pigment without any parasite. An ultrastructural study performed in 8 cases of active malaria infection showed characteristic features of trophozoites and schizontes, and malaria pigment. No viral particle were seen. We did not observe any significative difference concerning the incidence of chorioamnionitis and of malaria infection in 275 HIV negative placentas. In the literature as well as in the present study, the main lesions observed in the placentas of AIDS patients were chorioamnionitis. Opportunistic infections and neoplasias of the placenta are exceptional. Detection of HIV proteins by immunochemistry or in situ hybridization is possible, but the HIV could not be identified in the trophoblast by electron microscopy. Mechanisms of the materno-fetal transmission for HIV are currently unknown.

Acquired Immunodeficiency Syndrome↗

Characteristics of the infant thermal environment in the control population of a case-control study of SIDS.

This report examines the thermal environment during last sleep of a control population to investigate how the thermal environment of the infant's bedroom varies by season, external temperature and by certain maternal and infant characteristics. Two age-matched control infants were chosen for each case, one of which was also matched on birthweight. The home visits were not pre-arranged and were matched on climatic conditions, time of year and time period of day for the index case. The initial response rate for controls (n = 108) was 86%. Although there was a large amount of variation in the infant thermal environment, thermal insulation correlated with room temperature (r = -0.44, P = 0.0001) and external temperature (r = -0.30, P = 0.002). The thermal environment of the infant, as defined by excess thermal insulation for room temperature, did not vary by indoor or outdoor temperature, but higher average values were observed in teenage mothers (mean difference = 2.7 tog [95% Cl = 0.3, 5.2]), infants who slept in an adult bed (mean difference = 2.6 tog [-0.1, 5.4]) and infants with an illness (mean difference = 0.8 tog [-0.3, 1.9]). There was a tendency for the thermal environment of infants to be higher and more variable during winter, supporting previous hypotheses that paradoxical overheating may occur in some infants during winter. Further work is required to provide a set of recommendations on the optimal thermal conditions for post-neonatal infants.

Bedding and Linens↗

Pretransitional population control and equilibrium.

A persistent theme in much anthropological writing is the concept of the deliberate control of population numbers by hunter-gatherers as a means of achieving moderate family size, adequate nutrition, and constrained adult mortality. An analysis of the mix of theory and field evidence that led to this conclusion finds the case not proven. On the contrary, Malthusian constraints can operate, and probably did operate, to produce a hunter-gatherer society where most adults were reasonably robust and healthy even though child mortality was high and life expectancy short. The absence of population limitation in pre-Neolithic times implies high mortality as well as high fertility, and weakens the argument positing a Neolithic mortality crisis.

Demography↗

Cytogenetic monitoring of industrial populations potentially exposed to genotoxic chemicals and of control populations.

Currently the most applied technique for monitoring biological effects of exposure to genotoxic chemicals in industrial workers is the measurement of chromosome aberrations in peripheral blood lymphocytes. In the Shell petrochemical complex in The Netherlands cytogenetic monitoring studies have been carried out from 1976 till 1981 inclusive, in workers potentially exposed to a variety of genotoxic chemicals, i.e. vinyl chloride, ethylene oxide, benzene, epichlorohydrin, epoxy resins. Average exposure levels to these chemicals were well below the occupational exposure limits. Results of these studies indicate that no biologically significant increase in the frequencies of chromosome aberrations in the exposed populations occurred compared with control populations. Our experience with this methodology has shown that the results of chromosome analyses are difficult to interpret, due to the variable and high background levels of chromosome aberrations in control populations and in individuals. It is concluded that the method is not sufficiently sensitive for routine monitoring of cytogenetic effects in workers exposed to the low levels of genotoxic compounds.

Chromosome Aberrations↗

HLA-A3 and serum iron. A study in an Irish control population.

In a control population of 127 healthy adults in the West of Ireland, the possession of the HLA-antigens associated with idiopathic haemochromatosis (IH), i.e. HLA-A3, B7 and B14 was not accompanied by higher levels of serum iron, total iron binding capacity (TIBC) or transferrin saturation (TS%). HLA-A3 does not appear to confer enhanced ability to absorb dietary iron.

Adult↗

Microsatellite analysis of the Queensland fruit fly Bactrocera tryoni (Diptera: Tephritidae) indicates spatial structuring: implications for population control.

The population structure of a tephritid pest species, the Queensland fruit fly Bactrocera tryoni (Froggatt), has been analysed over a five year period (1994-1998), using six microsatellites. Adult fly samples were collected to cover most regions of eastern and central Australia where the flies are regularly found. Tests for heterogeneity indicated that flies within geographically defined regions were homogeneous. The samples were allocated into five regions, including one very large region, Queensland, which encompasses that portion of the fly's range where breeding can occur year-round. With one exception, the collections from different regions were homogeneous between years, showing a fairly static distribution of the species. However, differences between regions were highly significant. The one case of a change in frequency between years indicated a gradual replacement of flies in a marginal region by flies from the main part of the range. The finding of stability in the distribution of a highly mobile insect is of interest, potentially also for other species which have expanded beyond their native range. It is argued that a contributing reason for this stability may be adaptation to different climatic regimes, and that strategies for control based on this hypothesis afford a reasonable chance of success.

Animals↗

Hospital or population controls for case-control studies of severe childhood diseases?

There are few empirical data to determine which control group seems best in a case-control study for a severe disease: population controls or hospital controls. The author conducted a case-control study of leukemia in children using two control groups, population and hospital controls (cancers other than leukemia and severe blood diseases), between 1980 and 1993 in Québec, Canada. Maternal, paternal, and child factors not known to be associated with leukemia as well as factors possibly associated were selected for analysis. Most factors were taken directly from parental interviews, but two factors related to parental occupational exposures were blindly coded by chemists. Hospital and population controls were compared using odds ratios estimated from logistic regression. Cases were compared with both types of controls with the same statistical method. Prevalence data from ongoing population surveys were compared with reported prevalence in controls. From the former comparisons and the distribution of socioeconomic variables, results suggested that study groups came from the same base population. Nevertheless, reported and coded exposures among hospital controls were closer to those of cases than to those of population controls. Although substantially different for only one factor, inferences using hospital controls in comparison with population controls resulted in odds ratios closer to the null value.

Adult↗

Population control I: Birth of an ideology.

Population control, as a major international development strategy, is a relatively recent phenomenon. However, its origins reach back to social currents in the 19th and early 20th centuries, culminating in an organized birth control movement in Europe and the United States. The conflicts and contradictions in that movement's history presage many of today's debates over population policy and women's rights. Eugenics had a deep influence on the U.S. birth control movement in the first half of the 20th century. After World War II private agencies and foundations played an important role in legitimizing population control as a way to secure Western control over Third World resources and stem political instability. In the late 1960s the U.S. government became a major funder of population control programs overseas and built multilateral support through establishment of the U.N. Fund for Population Activities. At the 1974 World Population Conference, Third World governments challenged the primacy of population control. While their critique led population agencies to change their strategies, population control remained a central component of international development and national security policies in the United States.

Eugenics↗

Autoantibodies against MDA-LDL in subjects with severe and minor atherosclerosis and healthy population controls.

Autoantibodies against oxidized low-density lipoprotein (LDL) have been reported to be associated with atherosclerosis. However, data are not consistent. We compared the titres of autoantibodies to malondialdehyde-modified LDL in three groups, a case group with angiographically documented severe coronary stenosis (> 80% stenosis in at least 1 vessel, n = 47), a hospital control group with minor stenosis on the coronary angiography (< 50% stenosis in all three major vessels, n = 47) and a healthy population control group with no history of coronary heart disease (n = 49). Age ranged from 26 to 68 years. Subjects were frequency-matched for gender distribution and storage time of the blood samples. No relevant differences in autoantibody titre between case and control groups were found. The mean autoantibody titres (+/- S.D.) were 1.44 +/- 1.82, 1.46 +/- 1.40 and 1.62 +/- 1.95 for cases, hospital controls and population controls, respectively. No correlations were found between autoantibody titre and age, number of cigarettes smoked and LDL or total cholesterol. Autoantibody titres were correlated with body mass index (r = 0.2) and high-density lipoprotein (HDL) (r = -0.2). Odds ratios (OR) were calculated by tertiles of autoantibody titres for the hospital control group and the population control group, respectively. Age-adjusted OR (95% confidence interval) for medium and high compared to low autoantibody titre were 0.76 (0.27-2.14) and 1.09 (0.39-2.95) for the comparison between cases and hospital controls and 1.09 (0.39-3.07) and 0.90 (0.32-2.56) for the comparison between cases and population controls. Adjustment for gender, body mass index, smoking habits and HDL yielded essentially the same results. This study does not support an association between autoantibody titres to oxidized LDL and the extent of coronary stenosis.

Adult↗