64 general practitioners and 42 psychiatrists in central Norway answered a questionnaire which evaluated the doctors attitudes to benzodiazepines through their responses to 19 statements regarding these drugs. In addition, eight patient questionnaires were used to assess prescribing habits regarding benzodiazepines. There was considerable variation between the responses from the two groups of doctors. Psychiatrists exhibited significantly (p less than 0.001) more negative attitudes and stricter prescription habits as regards benzodiazepines than general practitioners did. Another finding was a significant and positive correlation between attitudes and prescribing habits.
Comment In: Tidsskr Nor Laegeforen. 1991 Oct 10;111(24):2998-91683027
Comment In: Tidsskr Nor Laegeforen. 1991 Sep 10;111(21):26771948858
When misclassification of exposure and disease is nondifferential but not independent of one another, bias away from the null can result. For dichotomous variables, misclassification is nonindependent when the probability of misclassification of one variable is dependent on the correctness of classification of the other variable. One plausible form of nonindependent misclassification may result from variation in the threshold for reporting exposure and outcome by study subjects. The odds ratio after dependent misclassification can be expressed as a function of the true odds ratio, the prevalences of exposure and outcome, and the probabilities of misclassification. When prevalences of exposure and outcome are low, bias may be considerable even at low probabilities of misclassification. The nonindependent misclassification described in this article will result in a positive bias in the odds ratio and is therefore of prime concern when questioning the validity of an observed effect. The core of the problem lies in the study design and can be solved by eliminating the common link that makes nonindependent errors possible.
We investigated birth defects (N = 4,565) reported to the Medical Birth Registry of Norway among 192,417 births between 1967 and 1991 to parents identified as farmers in five agricultural and horticultural censuses between 1969 and 1989. The prevalences at birth of all and specific birth defects deviated little from those among 61,351 births to non-farmers in agricultural municipalities. We classified exposure indicators on the basis of information provided at the agricultural censuses. The main hypotheses were that parental exposure to pesticides was associated with defects of the central nervous system, orofacial clefts, some male genital defects, and limb reduction defects. We found moderate increases in risk for spina bifida and hydrocephaly, the associations being strongest for exposure to pesticides in orchards or greenhouses [spina bifida: 5 exposed cases, odds ratio (OR) = 2.76, 95% confidence interval (CI) = 1.07-7.13; hydrocephaly: 5 exposed cases, OR = 3.49, 95% CI = 1.34-9.09]. Exposure to pesticides, in particular in grain farming, was also associated with limb reduction defects (OR = 2.50; 95% CI = 1.06-5.90). We also saw an association with pesticides for cryptorchism and hypospadias. We found less striking associations for other specific defects and pesticide indicators, animal farming, and fertilizer regimens.
In this study of cancer in offspring we demonstrate that factors linked to horticulture and use of pesticides are associated with cancer at an early age, whereas factors in animal husbandry, in particular poultry farming, are associated with cancers in later childhood and young adulthood. Incident cancer was investigated in offspring born in 1952-1991 to parents identified as farm holders in agricultural censuses in Norway in 1969-1989. In the follow-up of 323,292 offspring for 5.7 million person-years, 1,275 incident cancers were identified in the Cancer Registry for 1965-1991. The standardized incidence for all cancers was equal to the total rural population of Norway, but cohort subjects had an excess incidence of nervous-system tumours and testicular cancers in certain regions and strata of time that could imply that specific risk factors were of importance. Classification of exposure indicators was based on information given at the agricultural censuses. Risk factors were found for brain tumours, in particular non-astrocytic neuroepithelial tumours: for all ages, pig farming tripled the risk [rate ratio (RR), 3.11; 95% confidence interval (CI), 1.89-5.13]; indicators of pesticide use had an independent effect of the same magnitude in a dose-response fashion, strongest in children aged 0 to 14 years (RR, 3.37; 95% CI, 1.63-6.94). Horticulture and pesticide indicators were associated with all cancers at ages 0 to 4 years, Wilms' tumour, non-Hodgkin's lymphoma, eye cancer and neuroblastoma. Chicken farming was associated with some common cancers of adolescence, and was strongest for osteosarcoma and mixed cellular type of Hodgkin's disease. The main problem in this large cohort study is the crude exposure indicators available; the resulting misclassification is likely to bias any true association towards unity.
Clustering of deaths in a small, defined group of employees may occur by chance. Alternatively, the cause may be non-fortuitous, for example selection of risk individuals into the group, risk factors at work or in lifestyle. According to the Norwegian Working Environment Act it is the employer's duty to make the decision as to whether an observed cluster of deaths should have consequences for the working environment. The employer may feel a natural need for advice from specialists in order to take this decision. In many instances, the occupational health service will be a natural choice for the employer as a source of advice. At one work-place five out of a total of ten press consultants died between 1970 and 1988. The article describes a way to estimate the probability of the clustering being fortuitous. Fortuity is compared with other possibilities.
We used multistep register linkage to measure the occurrence of cancer in offspring of male members of the Oslo unions of printers. A file of their children was established through linkage with the Central Population Register. Children born 1950-1987 (N = 12,440) were traced for cancer during 1965-1987 in the Cancer Registry of Norway (193,406 person-years). We found 33 cases of cancer. The standardized incidence ratio was near expected for person-years after age 14 (25 cases observed) but lower than expected for person-years in the age group 0-14 years (eight cases observed, standardized incidence ratio 0.58, 95% confidence interval 0.25-1.14). This negative association was stronger when more precise criteria for time of exposure were applied, especially for children 0-14 years with fathers in categories exposed to lead 1 year before the child's birth. Methodologic problems with this approach are nondifferential exposure misclassification and the need for large data sets. The method could serve as an alternative to the case-control design in reproductive epidemiology.
In a national study of births to farmers in Norway, grain farming was associated with short gestational age (21-24 weeks). An impact of selective fertility and maternal heterogeneity on the association was suspected but could not be assessed further in a traditional birth-based design. Thus, analyses based on the mother as the observational unit were performed. A total of 45,969 farmers with a first birth in 1967-1981 were followed for subsequent births and perinatal mortality. A perinatal loss increased farmers' likelihood to continue to another pregnancy, but this selective fertility was less dominant than in the general population due to a higher baseline fertility. The effect of the mother's reproductive history on the grain farming-midpregnancy delivery association was analyzed in 59,338 farmers with more than one single birth in 1967-1991. A history of preterm birth (