Tone Bjørge

Body Mass Index in Adolescence in Relation to Cause-specific Mortality: A Follow-up of 230,000 Norwegian Adolescents

The prevalence of obesity in childhood and adolescence has increased worldwide. Long-term effects of adolescent obesity on cause-specific mortality are not well specified. The authors studied 227,000 adolescents (aged 14-19 years) measured (height and weight) in Norwegian health surveys in 1963-1975. During follow-up (8 million person-years), 9,650 deaths were observed. Cox proportional hazards regression was used to compare cause-specific mortality among individuals whose baseline body mass index (BMI) was below the 25th percentile, between the 75th and 84th percentiles, and above the 85th percentile in a US reference population with that of individuals whose BMI was between the 25th and 75th percentiles. Risk of death from endocrine, nutritional, and metabolic diseases and from circulatory system diseases was increased in the two highest BMI categories for both sexes. Relative risks of ischemic heart disease death were 2.9 (95% confidence interval (CI): 2.3, 3.6) for males and 3.7 (95% CI: 2.3, 5.7) for females in the highest BMI category compared with the reference. There was also an increased risk of death from colon cancer (males: 2.1, 95% CI: 1.1, 4.1; females: 2.0, 95% CI: 1.2, 3.5), respiratory system diseases (males: 2.7, 95% CI: 1.4, 5.2; females: 2.5, 95% CI: 1.4, 4.8), and sudden death (males: 2.2, 95% CI: 1.2, 4.3; females: 2.7, 95% CI: 1.1, 6.6). Adolescent obesity was related to increased mortality in middle age from several important causes.

Chlamydia trachomatis infection as a risk factor for invasive cervical cancer

Cervical carcinoma is a sexually transmitted disease most strongly linked with human‐papillomavirus (HPV) infection. We conducted a prospective sero‐epidemiologic study to evaluate the role of Chlamydia trachomatis infection in the development of cervical carcinoma, with invasive cancer as an end point. A nested case‐control study within a cohort of 530000 Nordic women was performed. Linking data files of 3 Nordic serum banks and the cancer registries of Finland, Norway and Sweden identified 182 women with invasive cervical carcinoma diagnosed during a mean follow‐up of 5 years after serum sampling. The serum samples of the cases and matched cancer‐free controls were analyzed for IgG antibodies to C. trachomatis, C. pneumoniae (a control microbe) and HPV types 16, 18 and 33, as well as for serum cotinine (an indicator of tobacco smoking). Serum antibodies to C. trachomatis were associated with an increased risk for cervical squamous‐cell carcinoma (HPV‐ and smoking‐adjusted OR, 2.2; 95% CI, 1.3–3.5). The association remained also after adjustment for smoking both in HPV16‐seronegative and ‐seropositive cases (OR, 3.0; 95% CI, 1.8–5.1; OR, 2.3, 95% CI, 0.8–7.0 respectively). No such association was found for C. pneumoniae. Our prospective study provides sero‐epidemiologic evidence that infection with C. trachomatis confers an increased risk for subsequent development of invasive squamous‐cell carcinoma of the uterine cervix. Int. J. Cancer 85:35–39, 2000.

Obesity in Adolescence and Adulthood and the Risk of Adult Mortality

Background: There are few long-term follow-up data on the relation between body mass index (BMI) in adolescence and in adulthood, and between adolescent BMI and adult mortality. The present study explores these relations. Methods: In Norwegian health surveys during 1963–1999, height and weight were measured for 128,121 persons in a standardized way both in adolescence (age 14–19 years) and 10 or more years later. Persons were followed for an average of 9.7 years after the adult measurement. Cox proportional hazard regression models were used to study the association between adolescent and adult BMI and mortality. Results: The odds ratio of obesity (BMI ≥30) in adulthood increased steadily with BMI in adolescence, from 0.2 for low BMI up to 16 for very high BMI. Very high adolescent BMI was associated with 30–40% higher adult mortality compared with medium BMI. Adjusting for adult BMI explained most of the association of adolescent obesity and mortality, especially among men. Adjustment for smoking did not change the results. Conclusions: Obesity in adolescence tends to persist into adulthood. Adolescent obesity is also connected to excess mortality, but this excess seems to be explained mostly by obesity in adulthood. High BMI in adolescence seems to be predictive of both adult obesity and mortality.

Height, body mass index, and prostate cancer: a follow-up of 950 000 Norwegian men

The present study explored body mass index (BMI), height, and risk of prostate cancer in a large Norwegian cohort of 950 000 men aged 20–74 years, whose height and weight were measured in a standardised way in the period 1963–1999. These were followed for an average of 21 years. The Cox proportional hazard models were used in the analyses. During follow-up, 33 300 histologically verified cases of prostate cancer were registered. The risk of prostate cancer increased by both BMI and height. The magnitude of the increase by BMI was modest, the relative risk (RR) of obese men (BMI⩾30) compared with normal weighted was 1.09 (95% CI: 1.04–1.15). However, the RR at age 50–59 years was 1.58 (95% CI: 1.29–1.94) in men being obese at about age 45 years compared with normal weighted men. The tallest men had an RR of 1.72 (95% CI: 1.46–2.04) compared with the shortest men. The overall effect of BMI on the incidence of prostate cancer was modest. The larger effect found in men aged 50–59 years might partly explain the previous inconsistent findings.

Blood Glucose and Risk of Incident and Fatal Cancer in the Metabolic Syndrome and Cancer Project (Me-Can): Analysis of Six Prospective Cohorts

Tanja Stocks and colleagues carry out an analysis of six European cohorts and confirm that abnormal glucose metabolism is linked with increased risk of cancer overall and at specific sites.

Height and body mass index in relation to total mortality

Background. The relation between body mass index (BMI) and mortality is not clear in the literature. An inverse relation between height and mortality has been suggested. We explore these relations in a very large cohort in Norway. Methods. We studied two million men and women, age 20–74 years, who were measured during 1963–2000. These persons were followed for an average of 22.1 years. We used Cox proportional hazard models in the analyses. Also, the optimal BMI (the BMI at the time of measurement that was subsequently related to the lowest mortality) was estimated. Results. Over the study period, 723,000 deaths were registered. The relative risk of death by BMI showed a J- or U-shaped curve, with the lowest rates of death at BMI between 22.5 and 25.0. In men, the optimal BMI increased from 21.6 when measured at age 20–29 to 24.0 when measured at age 70–74. In women, the optimal BMI was consistently higher, increasing from 22.2 to 25.7. Mortality decreased with increased height in men; in women, mortality decreased with height only up to heights of about 160–164 cm and then increased among the tallest women. Conclusions. The relation between BMI and mortality was J- or U-shaped, with the “optimal” BMI varying by age and sex. Height was inversely related to mortality in men and in women up to a height of 165 cm.

Metabolic Syndrome and Breast Cancer in the Me-Can (Metabolic Syndrome and Cancer) Project

Background: Few studies have assessed the metabolic syndrome (MetS) as an entity in relation to breast cancer risk, and results have been inconsistent. We aimed to examine the association between MetS factors (individually and combined) and risk of breast cancer incidence and mortality. Methods: Two hundred ninety thousand women from Austria, Norway, and Sweden were enrolled during 1974-2005, with measurements of height, weight, blood pressure, and levels of glucose, cholesterol, and triglycerides. Relative risks (RR) of breast cancer were estimated using Cox proportional hazards regression for each MetS factor in quintiles and for standardized levels (z-scores) and for a composite z-score for the MetS. Results: There were 4,862 incident cases of breast cancer and 633 deaths from breast cancer identified. In women below age 50, there was a decreased risk of incident cancer for the MetS (per 1-unit increment of z-score; RR, 0.83; 95% confidence interval, 0.76-0.90) as well as for the individual factors (except for glucose). The lowest risks were seen among the heaviest women. In women above age 60, there was an increased risk of breast cancer mortality for the MetS (RR, 1.23; 95% confidence interval, 1.04-1.45) and for blood pressure and glucose. The strongest association with mortality was seen for increased glucose concentrations. Conclusions: The MetS was associated with a decreased risk of incident breast cancer in women below age 50 with high body mass index, and with an increased risk of breast cancer mortality in women above 60. Impact: Lifestyle interventions as recommended for cardiovascular disease prevention may be of value to prevent breast cancer mortality in postmenopausal women. Cancer Epidemiol Biomarkers Prev; 19(7); 1737–45. ©2010 AACR.

Human papillomavirus infection as a risk factor for anal and perianal skin cancer in a prospective study

Human papillomavirus has emerged as the leading infectious cause of cervical and other anogenital cancers. We have studied the relation between human papillomavirus infection and the subsequent risk of anal and perianal skin cancer. A case–cohort study within two large Nordic serum banks to which about 760 000 individuals had donated serum samples was performed. Subjects who developed anal and perianal skin cancer during follow up (median time of 10 years) were identified by registry linkage with the nationwide cancer registries in Finland and Norway. Twenty-eight cases and 1500 controls were analysed for the presence of IgG antibodies to HPV 16, 18, 33 or 73, and odds ratios of developing anal and perianal skin cancer were calculated. There was an increased risk of developing anal and perianal skin cancer among subjects seropositive for HPV 16 (OR=3.0; 95%CI=1.1–8.2) and HPV 18 (OR=4.4; 95%CI=1.1–17). The highest risks were seen for HPV 16 seropositive patients above the age of 45 years at serum sampling and for patients with a lag time of less than 10 years. This study provides prospective epidemiological evidence of an association between infection with HPV 16 and 18 and anal and perianal skin cancer.Human papillomavirus has emerged as the leading infectious cause of cervical and other anogenital cancers. We have studied the relation between human papillomavirus infection and the subsequent risk of anal and perianal skin cancer. A case–cohort study within two large Nordic serum banks to which about 760 000 individuals had donated serum samples was performed. Subjects who developed anal and perianal skin cancer during follow up (median time of 10 years) were identified by registry linkage with the nationwide cancer registries in Finland and Norway. Twenty-eight cases and 1500 controls were analysed for the presence of IgG antibodies to HPV 16, 18, 33 or 73, and odds ratios of developing anal and perianal skin cancer were calculated. There was an increased risk of developing anal and perianal skin cancer among subjects seropositive for HPV 16 (OR=3.0; 95%CI=1.1–8.2) and HPV 18 (OR=4.4; 95%CI=1.1–17). The highest risks were seen for HPV 16 seropositive patients above the age of 45 years at serum sampling and for patients with a lag time of less than 10 years. This study provides prospective epidemiological evidence of an association between infection with HPV 16 and 18 and anal and perianal skin cancer.

Body size in relation to cancer of the uterine corpus in 1 million Norwegian women

A positive association between overweight/obesity and endometrial cancer has been observed. It has been hypothesized that obesity is mostly associated with a subtype described as estrogen‐dependent (Type I tumors), constituting about 80% of the endometrial tumors. Few epidemiologic studies have, however, analyzed different histological subtypes separately. The present study aimed at exploring the relations between body size and histological subtypes of cancer of the uterine corpus. Height and weight were measured in over 1 million Norwegian women aged 20–74 during 1963–2001. During follow‐up, 9,227 cancers of the uterine corpus were diagnosed. The tumors were classified as Type I tumors (mostly endometrial adenocarcinomas with subgroups), Type II tumors (papillary, serous, and clear cell adenocarcinomas and some poorly differentiated carcinomas), sarcomas, and mixed tumors. Relative risks (RRs) of cancer of the uterine corpus were estimated using Cox proportional hazards regression. Compared with women with normal BMI, overweight and obese women had an overall RR of cancer of the uterine corpus of 1.36 (95% CI: 1.29–1.42) and 2.51 (95% CI: 2.83–2.66). The increase in risk was most pronounced for Type I tumors, but was also seen for Type II tumors, sarcomas and mixed tumors. The overall RR of corpus uteri cancer associated with a 10‐cm increase in height was 1.09 (95% CI: 1.05–1.13), and was mostly observed for Type I tumors.

Body size and thyroid cancer in two million Norwegian men and women

We investigated relations between measured body mass index (BMI) and stature and thyroid cancer (3046 cases) in a large Norwegian cohort of more than two million individuals. The risk of thyroid cancer, especially of the papillary and follicular types, increased moderately with increasing BMI and height in both sexes.