Grethe Albrektsen

Breast cancer risk by age at birth, time since birth and time intervals between births: exploring interaction effects

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.

School-Related Stress Experience as a Risk Factor for Bullying Behavior

Associations between bullying behavior and school-related stress experience, self-efficacy, social support, and decision control were explored in a study of 885 Norwegian adolescents aged 13–15 years. Information was based on self-reports. The psychosocial factors were represented by an average of scores on 3–12 single items, each with 5 possible response categories. Bullying behavior was defined as bullying other pupils sometimes or more often during the term. The prevalence of bullying behavior was 9.2%, but significantly higher among boys than girls. Odds ratios of bullying behavior according to psychosocial factors were calculated in a multiple logistic regression analysis. Increasing school alienation was associated with an increased risk of bullying, whereas increasing support from teachers and peers decreased the risk. Increasing self-efficacy was associated with a significant increase in risk only among 14-year-old pupils, but a similar tendency was seen for 15-year-old pupils. No significant association was seen with decision control.

The short-term and long-term effect of a pregnancy on breast cancer risk : a prospective study of 802 457 parous Norwegian women

Time-related effects of a pregnancy on breast cancer risk were examined in a population-based prospective study of 802,457 parous Norwegian women aged 20-56 years. The mean follow-up time was 16.4 years. A total of 4787 women were diagnosed with breast cancer. We observed a short-term increase in risk of breast cancer after a full-term pregnancy, with a maximum 3-4 years after delivery, followed by a long-lasting decrease in risk. The maximum risk was about twice the risk for women whose last delivery was 20 or more years previously (incidence rate ratio = 1.99, 95% confidence interval = 1.70-2.33). Compared with nulliparous women, those with one or two children were at higher risk in the first decade after the last pregnancy, whereas those with three or more children were at lower risk in most categories of time since the last birth. The positive association between breast cancer risk and age at last birth was markedly reduced after adjustment for time since last birth. We conclude that there is a non-linear relationship between breast cancer incidence and time since last birth. Part of the relation with age at last birth may be attributed to the association with time since last birth.

Psychosomatic Symptoms among Victims of School Bullying

Associations between being a victim of bullying and psychosomatic health have been examined among 856 Norwegian school adolescents aged 13 to 15 years. Multiple logistic and linear regression analyses were applied. Pupils being bullied sometimes or more often during the previous term had significantly higher odds of every psychosomatic symptom except sleeplessness, compared to pupils who reported that they were never exposed to bullying. The highest odds ratio was observed in analysis of feeling low. No significant interactions with gender or age were seen, but the association with irritability, headache and backache tended to be strongest for boys, whereas the association with nervousness and sleeplessness was strongest for girls. Increasing exposure to bullying was associated with a highly significant increase in number of symptoms. The strong and consistent associations with different symptoms and the dose–response relationship suggest a causal relationship.

Quality of life, perceived difficulties in adherence to a diabetes regimen, and blood glucose control

The first aim of the present study was to investigate if self‐assessed quality of life was associated with perceived difficulties in adherence to a regimen, and the second, if perceived difficulties in adherence were associated with poor blood glucose control. A self‐administered questionnaire was completed by 247 patients with Type 1 diabetes who consecutively attended a Norwegian diabetes clinic. Results from multiple linear regression analysis indicated that a higher level of quality of life was associated with greater perceived ease of adherence to the regimen. Adherence to control of smoking, increased physical exercise, and control of weight and diet were perceived as most difficult. Analysis of covariance showed that women who perceived difficulties in adherence to self‐care behaviour had on average less satisfactory blood glucose control than those reporting less difficulty in adherence.

Clinical stage of breast cancer by parity, age at birth, and time since birth: a progressive effect of pregnancy hormones?

Breast cancer diagnosed during pregnancy or 1 to 2 years after birth often occurs at a late stage. Little is known about tumor characteristics in the high-risk period shortly after a childbirth. We here explore whether stage of disease differs according to timing of births. Results are based on 22,351 Norwegian breast cancer patients of parity 0 to 5, ages 20 to 74 years. The proportion of stage II to IV tumors was considerably higher among parous than nulliparous women at age <30 years (52.7% versus 36.8%, P = 0.009), but similar or lower in other age groups (Pinteraction = 0.029). In general, the largest proportion of stage II to IV tumors was found among women diagnosed during pregnancy or <2 years after birth. However, among women with late-age births (first or second birth ≥30 years, third birth ≥35 years), as well as women with an early second birth (<25 years), the proportion with advanced disease was rather similar or even higher among those diagnosed 2 to 6 years after birth (49.3-56.0%). The association between clinical stage and time since birth reached statistical significance among women with a late first or second birth and among all triparous women (P ≤ 0.032). The subgroups with a high proportion of advanced disease 2 to 6 years after birth corresponded quite well to those previously found to have the most pronounced transient increase in risk after birth. Thus, pregnancy hormones may have a progressive effect on breast cancer tumors in addition to a possible promoting effect. A potential effect of prolactin is discussed. (Cancer Epidemiol Biomarkers Prev 2006;(15)1:65–9)

Reproductive factors and incidence of epithelial ovarian cancer: a Norwegian prospective study.

To examine relations between the risk of epithelial ovarian cancer and time-related effects of pregnancies, we analyzed data from a prospective study of 1,145,076 women in Norway aged 20 to 56 years. The mean follow-up time per woman was 16.4 years and a total of 1,694 women were diagnosed with epithelial ovarian cancer. Incidence rate ratios (IRR) were estimated by Poisson regression analysis of person-years at risk. The risk of epithelial ovarian cancer decreased with an increasing number of full-term pregnancies (IRR=0.56,95 percent confidence interval = 0.48–0.67 for three pregnancies cf one). However, no further reduction in risk was seen after the third pregnancy. The association with parity became weaker with increasing age at last birth. Further, the reduction in risk among parous women compared with nulliparous women was more pronounced shortly after birth. Both higher age at last birth and shorter time since last birth were associated with a reduction in risk, although these relations were seen mainly for the first and second births. Increasing age at first birth was associated with a decrease in risk among uniparous women but not among multiparous women. Our results indicate that the relations between the incidence of epithelial ovarian cancer and reproductive factors are more complex than previously believed.

Breast cancer incidence before age 55 in relation to parity and age at first and last births: a prospective study of one million Norwegian women.

We examined the relation between breast cancer, parity 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. (Epidemiology 1994;5:604–611)

Histological type and grade of breast cancer tumors by parity, age at birth, and time since birth: a register-based study in Norway

BackgroundSome studies have indicated that reproductive factors affect the risk of histological types of breast cancer differently. The long-term protective effect of a childbirth is preceded by a short-term adverse effect. Few studies have examined whether tumors diagnosed shortly after birth have specific histological characteristics.MethodsIn the present register-based study, comprising information for 22,867 Norwegian breast cancer cases (20-74 years), we examined whether histological type (9 categories) and grade of tumor (2 combined categories) differed by parity or age at first birth. Associations with time since birth were evaluated among 9709 women diagnosed before age 50 years. Chi-square tests were applied for comparing proportions, whereas odds ratios (each histological type vs. ductal, or grade 3-4 vs. grade 1-2) were estimated in polytomous and binary logistic regression analyses.ResultsDuctal tumors, the most common histological type, accounted for 81.4% of all cases, followed by lobular tumors (6.3%) and unspecified carcinomas (5.5%). Other subtypes accounted for 0.4%-1.5% of the cases each. For all histological types, the proportions differed significantly by age at diagnoses. The proportion of mucinous and tubular tumors decreased with increasing parity, whereas Paget disease and medullary tumors were most common in women of high parity. An increasing trend with increasing age at first birth was most pronounced for lobular tumors and unspecified carcinomas; an association in the opposite direction was seen in relation to medullary and tubular tumors. In age-adjusted analyses, only the proportions of unspecified carcinomas and lobular tumors decreased significantly with increasing time since first and last birth. However, ductal tumors, and malignant sarcomas, mainly phyllodes tumors, seemed to occur at higher frequency in women diagnosed <2 years after first childbirth. The proportions of medullary tumors and Paget disease were particularly high among women diagnosed 2-5 years after last birth. The high proportion of poorly differentiated tumors in women with a recent childbirth was partly explained by young age.ConclusionOur results support previous observations that reproductive factors affect the risk of histological types of breast cancer differently. Sarcomas, medullary tumors, and possible also Paget disease, may be particularly susceptible to pregnancy-related exposure.

Self-assessed Quality of Life and Metabolic Control in Persons with Insulin-Dependent Diabetes Mellitus (IDDM)

The aim of the study was to analyse the association between satisfaction with life and glycosylated haemoglobulin (MbAl). A quality of life questionnaire was administered to 247 persons with IDDM at a Diabetic Clinic in Bergen, Norway. The material was divided into two groups depending on their level of HbAl; HbAl > 0.09 was labelled poorly regulated and a level of HbAl ≥ 0.09 was labelled well regulated. The groups were compared with regard to different life domains and well-being scales. The statistical analysis showed that the well-regulated group had significantly higher average scores considering the somatic and activity/behavioural life domain ratings, the latter being only significantly different among people with higher education. The well-gegulated group had lower average scores in the psychological and social life domain ratings, but these differences were not statistically significant. Among the well-being scales we found a statistically significant difference between poor and well-regulated persons only regarding sociability and loneliness. Well-regulated persons felt on average less sociable and more lonely than poorly-regulated persons.