A population-based case-control study was conducted in Sweden and Norway to analyse possible associations between breast cancer occurring before the age of 45 and several different characteristics of the women's reproductive life. A total of 422 (89.2%) of all eligible patients, and 527 (80.6%) of all eligible controls were interviewed. In univariate analyses, different characteristics of child-bearing (parity, age at first birth, years between last birth and diagnosis, duration of breast-feeding, and number of induced and spontaneous abortions), measures of the fertile or ovulating period (age at menarche, years between menarche and first pregnancy, and estimates of the menstruation span) and symptoms of anovulatory cycles or infertility were all seemingly unrelated to, or at most weakly associated with breast cancer. Adjustment for possible confounding factors in multivariate analyses resulted in largely unaltered risk estimates with odds ratios close to unity and without any significant trends when the exposure variables were studied in categorised or in continuous form. We conclude that reproductive factors did not explain the occurrence of breast cancer before the age of 45 in this population.
The influence of age on survival was studied in an unselected series of 31,594 females with breast cancer reported to The Cancer Registry of Norway during 1955-1980. The prognosis was best in patients aged 35 to 49 years, and poorest in the older (greater than or equal to 75 years) and the younger patients (less than or equal to 34 years). These trends were present in all stages and periods of diagnosis. The poor outcome among the older patients may, in part, be related to less aggressive treatment, while differences in treatment procedures hardly explain the poor prognosis among the younger patients.
Several large epidemiological studies in the Nordic countries have failed to confirm an association between age at first birth and breast cancer independent of parity. To assess whether lack of power or heterogeneity between the countries could explain this, a meta-analysis was performed of 8 population-based studies (3 cohort and 5 case-control) of breast cancer and reproductive variables in the Nordic countries, including a total of 5,568 cases. It confirmed that low parity and late age at first birth are significant and independent determinants of breast-cancer risk. Nulliparity was associated with a 30% increase in risk compared with parous women, and for every 2 births, the risk was reduced by about 16%. There was a significant trend of increasing risk with increasing age at first birth, women giving first birth after the age of 35 years having a 40% increased risk compared to those with a first birth before the age of 20 years. Tests for heterogeneity between studies were not significant for any of the examined variables. In the absence of bias, this suggests that several individual Nordic studies may have had too little power to detect the weak effect of age at first birth observed in the meta-analysis.
The effect of airborne pollution, especially nickel, from Kola has been studied in 10,612 persons who participated in a cardiovascular screening survey in Finnmark in 1974-75. The age-range was 35-49 years and a follow-up for death was conducted up to 1985. Men living in the community of Sør-Varanger (close to the border) had a relative risk (RR) for death from diseases of 1.2 (95% confidence intervall; 0.9-1.6) compared with the rest of Finnmark, for women RR = 1.1. The increase in mortality for men was due to infactus cordis RR = 1.5 (1.0-2.4), and was not consistent for women (RR = 0.9). The study does not support the view that air pollution in this area has increased the risk of death.
Body height and weight in relation to breast cancer in women younger than 45 years were investigated in a case-control study in Sweden and Norway. The study included 317 Swedish and 105 Norwegian cases diagnosed in 1984-85 with 317 Swedish and 210 Norwegian age-matched population controls. Neither height nor body size, measured as body mass index, was associated with breast cancer. Change in body mass from the age of 20 years to 18 months before the time of diagnosis (cases) or interview (controls) had no effect on breast cancer risk. The study provides no evidence that anthropometric measures are risk factors for breast cancer in young women, indicating that the postulated inverse relationship between body mass index and pre-menopausal breast cancer could be limited to peri-menopausal women.
Swedish studies have shown that experience of using snus is associated with an increased probability of being a former smoker. We examined whether this result is also found in Norway.
Seven cross-sectional data sets collected during the period 2003-08.
A total of 10, 441 ever (current or former) smokers.
Quit ratios for smoking were compared for people with different histories of snus use. Motive for snus use was examined among combination users (snus and cigarettes). Smoking status was examined among snus users.
Compared to smokers with no experience of using snus, the quit ratio for smoking was significantly higher for daily snus users in six of seven data sets, significantly higher for former snus users in two of five data sets and significantly lower for occasional snus users in six of seven data sets. Of combination users who used snus daily, 55.3% [confidence interval (CI) 44.7-65.9] reported that their motive for using snus was to quit smoking totally. This motive was reported significantly less often by combination users who used snus occasionally (35.7%, CI 27.3-44.2). Former smokers made up the largest proportion of daily snus users in six of seven data sets. In the remaining data set, that included only the age group 16-20 years, people who had never smoked made up the largest segment of snus users.
Consistent with Swedish studies, Norwegian data shows that experience of using snus is associated with an increased probability of being a former smoker. In Scandinavia, snus may play a role in quitting smoking but other explanations, such as greater motivation to stop in snus users, cannot be ruled out.
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BACKGROUND: Previous studies have shown that the prevalence of asthma and allergy in children is lower in Eastern than Western Europe. METHODS: We have compared the prevalence of asthma, respiratory symptoms, allergic rhinoconjunctivitis, and atopic dermatitis in schoolchildren aged 7-13 years in a questionnaire-based study conducted in the city of Nikel on the Kola Peninsula, Russia, in 1994 (n = 1143) and another conducted in northern Norway in 1995 (n = 8676). RESULTS: The prevalence of diagnosed asthma was 5.1% in Russian children and 8.6% in Norwegian children; RR =0.58 (95% CI: 0.44-0.76). The prevalence of all respiratory symptoms was higher in Russian children. The prevalence of allergic rhinoconjunctivitis was 16.9%, in Russian children and 22.1%, in Norwegian children: RR =0.74 (95% CI: 0.65-0.85). The prevalence of atopic dermatitis was 7.4% in Russian children and 19.7% in Norwegian children; RR=0.38 (95% CI: 0.31-0.46). CONCLUSIONS: We conclude that the prevalence of diagnosed asthma, allergic rhinoconjunctivitis, and atopic dermatitis was higher in Norwegian than Russian schoolchildren. The higher prevalence of respiratory symptoms in Russian children probably reflects a higher prevalence of undiagnosed, nonallergic asthma.
Among children in the western world, atopic diseases are a major cause of morbidity. However, several prevalence studies have indicated that the frequency of these diseases displays both geographic and ethnic variations. In 1995, we conducted a questionnaire-based, cross-sectional survey in northern Norway. Atopic diseases among 8676 schoolchildren, aged 7-13 years, including 491 children with Sami ethnicity, were studied. The role of ethnicity (Sami/white Caucasian) was determined by comparing the reported atopic disease rate in each of the respective groups. In the areas under investigation (the cumulative incidence, the point prevalence of asthma and allergic rhinoconjunctivitis and the cumulative incidence of atopic dermatitis), the Sami children scored higher than the white Caucasian Norwegian children. The relative risks (RR) in Sami children were: current asthma RR = 2.01 [95% confidence interval (CI) 1.48-2.73]; current allergic rhinoconjunctivitis RR = 1.51 (95% CI 1.14-1.99); lifetime atopic dermatitis RR = 1.39 (95% CI 1.18-1.63). We thus conclude that there is an association between Sami ethnicity and asthma and allergy among schoolchildren in northern Norway.
Several studies have concluded that atopy is more common in Western than in Eastern Europe. We aimed to study whether a similar difference exists between Norwegian and Russian adults living in geographically adjacent areas.
A cross-sectional population-based study was performed in Sør- Varanger municipality (Norway) and in the cities of Nikel and Zapolyarny (Russia). The Russian cities are heavily polluted by sulfur dioxide from local nickel industry. In addition to questionnaire information, results on IgE sensitization (S-Phadiatop, Pharmacia & Upjohn, Uppsala, Sweden) were obtained from 3134 Norwegian and 709 Russian participants.
A positive Phadiatop was found in 20.7% of the Norwegians (men 21.9%, women 19.7%) and in 27.5% of the Russians (men 35.7%, women 23.0%); the sex- and age-adjusted relative risk of testing positive in Russia being 1.49 (95% CI 1.23-1.81). The Norwegian participants reported more atopic dermatitis and hay fever, although this difference was statistically significant only for atopic dermatitis in women.
IgE sensitization was more common in Russia than in Norway, unlike findings from other east-west European studies. The Russians did not, however, report more atopic diseases. This discrepancy might reflect different awareness of allergies in the two countries and demonstrates the need for objective markers of atopy when comparing prevalence in different populations.
BACKGROUND: Delivering women and their newborns in the Kola Peninsula of Russia and the neighboring arctic area of Norway were studied to explore relationships between maternal cadmium and lead status and birth weight as a pregnancy outcome. METHODS: Life-style information, maternal blood and cord blood specimens were collected from 50 consecutive mother-infant pairs from hospital delivery departments in three Russian and three Norwegian communities. Pregnancy outcomes were verified by consulting medical records. Lead and cadmium were determined in the blood samples by electrothermal atomic absorption spectrometry. RESULTS: The median blood-cadmium concentration for the Russian mothers was 2.2 nmol/L (n = 148) versus 1.8 nmol/L in the Norwegian group (n = 114, p = 0.55). A weak association was observed between maternal cadmium and amount smoked (r = 0.30, p