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.
Relationships between incidence of Wilms' tumour and information recorded at birth were investigated in a prospective study of the 1,489,297 children born in Norway between 1967 and 1992. A total of 119 individuals were diagnosed with Wilms' tumour in the age interval 0-14 years. A high length at birth was significantly associated with a high risk (incidence rate ratio 1.8 for length > or = 53 cm vs or = 9, 95% CI 1.2-3.9). For all variables for which an association was indicated, the association seemed to be restricted mainly to children aged less than 2 years. This suggests that Wilms' tumour diagnosed early in life may differ aetiologically from that of cases diagnosed later.
We examined the relation between breast cancer, parity, and age at first and last births in a large national cohort of young women in Norway. We estimated relative incidence rates by Poisson regression analyses of person-years at risk with parity and age at last (most recent) birth as time-dependent variables. A total of 1,071,795 women were included in follow-up, contributing a total of 16,643,883 person-years in the age range 20-54 years. Follow-up times ranged from 1 month to 34.5 years. A total of 4,302 women were diagnosed with breast cancer during follow-up. With adjustment for age at first and last births, high parity was associated with an overall reduced risk of breast cancer (incidence rate ratio = 0.46; 95% confidence interval = 0.36-0.59 for women with five or more children vs uniparous women). Among women age 20-29 years, however, the results suggested an increase in risk with increasing parity (incidence rate ratio = 1.25; 95% confidence interval = 0.64-2.45 for women with three children vs uniparous women). The protective effect of high parity was particularly strong among women with first birth before the age of 20 years and rather weak among those with first birth at age 30 years or more. Low ages at first and last births were both associated with reduced breast cancer risk in analyses with adjustment for the other factor, with the association with age at last birth being slightly stronger.
In a Norwegian, prospective study we investigated breast cancer risk in relation to age at, and time since, childbirth, and whether the timing of births modified the risk pattern after delivery. A total of 23,890 women of parity 5 or less were diagnosed with breast cancer during follow-up of 1.7 million women at ages 20-74 years. Results, based on Poisson regression analyses of person-years at risk, showed long-term protective effects of the first, as well as subsequent, pregnancies and that these were preceded by a short-term increase in risk. The magnitude and timing of this adverse effect differed somewhat by birth order, maternal age at delivery and birth spacing. No transient increase in risk was seen shortly after a first birth below age 25 years, but an early first birth did not prevent a transient increase in risk after subsequent births. In general, the magnitude of the adverse effect was strongest after pregnancies at age 30 years or older. A wide birth interval was also related to a more pronounced adverse effect. Increasing maternal age at the first and second childbirth was associated with an increase in risk in the long run, whereas no such long-term effect was seen with age at higher order births.
STUDY OBJECTIVE--The aim was to correlate the level of education to childbearing pattern and previous use of oral contraceptives in middle aged women. DESIGN AND SETTING--The study was a cross sectional survey of 3608 women aged 40-42 years in a county in northern Norway and involved 72% of all women in the age bracket living in the county. Information about childbearing and use of oral contraceptives was obtained from a self administered questionnaire. MAIN RESULTS--Level of education was inversely associated with parity and positively related to age at first and last birth, to the use of oral contraceptives at any time, and particularly to the use of oral contraceptives before the first birth. CONCLUSIONS--Women with high level of education have relatively low parity and postpone childbearing by using oral contraceptives.
We studied the distribution of MS cases in the county of Hordaland, Western Norway. The total MS population comprised 426 patients. The prevalence on January 1st, 1963, and on January 1st, 1983, and the average annual incidence in the period 1963-1982 were all lower in the coastal area compared to the inland area. An increase in incidence started in the urban area and was followed some 10 years later in the rural area. The Knox method revealed no statistically significant evidence of clustering either for time/place of onset or for time/place of birth. Indications of clustering according to year of onset were, however, observed in the rural area.
The health consequences of coffee drinking remain controversial. We report on an association between coffee consumption and the concentration of total homocysteine (tHcy) in plasma, a risk factor for cardiovascular disease and for adverse pregnancy outcome. The study population consisted of 7589 men and 8585 women 40-67 y of age and with no history of hypertension, diabetes, ischemic heart disease, or cerebrovascular disease. They were recruited from Hordaland county of western Norway in 1992-1993. Daily use of coffee was reported by 89.1% of the participants, of whom 94.9% used caffeinated filtered coffee. There was a marked positive dose-response relation between coffee consumption and plasma tHcy, which was stronger than the relation between coffee and total serum cholesterol. In 40-42-y-old men, mean tHcy was 10.1 mumol/L for nonusers and 12.0 mumol/L for drinkers of > or = 9 cups of coffee/d. Corresponding tHcy concentrations in 40-42-y-old women were 8.2 and 10.5 mumol/L, respectively. Although coffee drinking was associated with smoking and lower intake of vitamin supplements and fruit and vegetables, the coffee-tHcy association was only moderately reduced after these variables were adjusted for. The combination of cigarette smoking and high coffee intake was associated with particularly high tHcy concentrations. A strong inverse relation between tea and tHcy concentration in univariate analysis was substantially attenuated after smoking and coffee drinking were adjusted for. The results of the present report should promote future studies on tHcy as a possible mediator of adverse clinical effects related to heavy coffee consumption.
Comment In: Am J Clin Nutr. 1997 Dec;66(6):1475-79394702
Relationships between coffee consumption and occurrence of cancer as well as mortality were explored in a Norwegian study of 13,664 men and 2,891 women who in 1967-69 reported their coffee consumption. No statistically significant positive associations were found between coffee consumption and disease. A weak negative association was found with total cancer incidence even when the first 4 of the 11 1/2 years of follow-up were excluded, and strong negative associations with coffee drinking were noted for cancer of the kidney and nonmelanoma skin cancer. For cancer of the pancreas and bladder, no increase in incidence was found among those with a high coffee consumption. In subjects less than 65 years of age at start of follow-up, coffee drinking showed a significant inverse association with colon cancer.
The purpose of this survey was to evaluate the effects of smoking and occupational exposures on the decline in forced expiratory volume in one second (FEV1), and the presence of airflow limitation (FEV1 x100/forced vital capacity (FVC) being
Comment In: Eur Respir J. 1993 Sep;6(8):1088-98224120
Continued studies of frequency trends in carefully selected sites around the world can provide clues to the cause of multiple sclerosis (MS).
Based on information from three different, semi-independent sources of information, we have examined the temporal trends in the average annual age-adjusted rates of disability pension incidence, mortality, and incidence of MS from 1966 to 1991 in Møre and Romsdal County, Norway.
The average annual age-adjusted disability pension incidence rates (1966-68 = 3.62/100,000; 1990-91 = 7.33/100,000), the mortality rates (1966-68 = 0.91/100,000; 1990-91 = 1.88/100,000), and the incidence rates (1966-68 = 4.22/100,000; 1990-91 = 5.02/100,000) all showed a statistically significant increase. The difference in the development of MS-specific disability pension prevalence rates in the county compared to the nation is notable.
We consider that the increase in disability pension incidence, mortality, and incidence of MS is of biological significance. Thus three different sources of information corroborate corresponding trends indicating that better case ascertainment and improved diagnostic facilities only partially can explain the reported MS increase in western Norway.