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BACKGROUND Although a family history of schizophrenia is the best-established risk factor for schizophrenia, environmental factors such as the place and season of birth may also be important. METHODS Using data from the Civil Registration System in Denmark, we established a population-based cohort of 1.75 million persons whose mothers were Danish women(More)
BACKGROUND Compelling evidence suggests that childhood leukemia often originates in utero. Birth weight is one of the few pregnancy-related risk factors that has been associated with leukemia risk, but the association has remained poorly characterized. We conducted a population-based case-control study in Denmark, Sweden, Norway, and Iceland to investigate(More)
OBJECTIVE To study trends in multiple pregnancies not explained by changes in maternal age and parity patterns. DESIGN Trends in population based figures for multiple pregnancies in Denmark studied from complete national records on parity history and vital status. POPULATION 497,979 Danish women and 803,019 pregnancies, 1980-94. MAIN OUTCOME MEASURES(More)
BACKGROUND Parasitic helminth infections can protect against allergic airway inflammation in experimental models and have been associated with a reduced risk of atopy and a reduced course of asthma in some observational studies. Although no clinical evidence exists to support the use of helminth therapy for allergic disease, the helminth Trichuris suis has(More)
BACKGROUND The occurrence of acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML) during childhood may be influenced by factors operating in fetal life. Furthermore, childhood ALL has been suggested to be linked to patterns of infection during infancy. PURPOSE To explore these hypotheses and other associations, we studied the impact of(More)
Multiple sclerosis (MS) is known to accumulate within families. The magnitude of the familial risk, however, remains uncertain. Using a nationwide MS register and other national registers, the authors estimated relative and absolute risks of MS in a population-based cohort that included 19,615 first-degree relatives of 8,205 Danish MS patients followed from(More)
BACKGROUND It has been proposed that infections, perhaps prenatal exposure to the influenza virus, might increase the risk of schizophrenia. To address this hypothesis, we studied the possible influence on schizophrenia risk of sibship characteristics and ecological influenza prevalence data. Birth order and influenza prevalence were used as proxy measures(More)
BACKGROUND It has been proposed that early age at exposure to common childhood infections is associated with a decreased risk of allergy. Previous studies on the possible association between allergy and infection with measles, mumps, rubella, and varicella have not been conclusive as most did not include information on exact age at exposure. The objective(More)
BACKGROUND An increase in the prevalence of hypospadias has been reported, but the environmental causes remain virtually unknown. OBJECTIVES Our goal was to assess the association between risk of hypospadias and indicators of placental function and endogenous hormone levels, exposure to exogenous hormones, maternal diet during pregnancy, and other(More)
There are several reports of familial testicular cancer in the literature but few systematic attempts have been made to estimate the risk of testicular cancer in first-degree relatives of patients with this neoplasm, and the risk remains to be fully assessed in population-based studies. By means of data from the Danish Cancer Registry, we identified all(More)