Jeppe Friborg

Frequency of atopy in the Arctic in 1987 and 1998.

Few studies have measured the frequency of atopy with objective measures, and most of these studies have been done in industrialised countries. We analysed serum samples from 859 15-80-year-old Greenlanders who had participated in population-based screening campaigns in 1987 and in 1998. We defined atopy as a positive result in an assay that tests for specific IgE against the eight most common inhalant allergens in one pool (grass, birch, mugwort, dog, cat, horse, Cladosporum herbarum, house dust mite). The frequency of atopy doubled between 1987 (39 [10%] of 392) and 1998 (87 [19%] of 467; risk ratio 1.88 [95% CI 1.31-2.68]). This increase was largest in 15-19-year olds, but also occurred in older people, suggesting that the risk factors responsible for the increase in atopy do not operate only in childhood.

Cancer patterns in Inuit populations

Inuit people inhabit the circumpolar region, with most living in Alaska, northwest Canada, and Greenland. Although malignant diseases were believed to be almost non-existent in Inuit populations during the beginning of the 20th century, the increasing life expectancy within these populations showed a distinct pattern, characterised by a high risk of Epstein-Barr virus-associated carcinomas of the nasopharynx and salivary glands, and a low risk of tumours common in white populations, including cancer of the prostate, testis, and haemopoietic system. Both genetic and environmental factors seem to be responsible for this pattern. During the second half of the 20th century, Inuit societies underwent major changes in lifestyle and living conditions, and the risk of lifestyle-associated tumours, especially cancers of the lung, colon, and breast, increased considerably after changes in smoking, diet, and reproductive factors. This Review will briefly summarise the current knowledge on cancer epidemiology in Inuit populations, with emphasis on the characteristic Inuit types of cancer.

Cancer in Greenlandic Inuit 1973–1997: A cohort study

The increasing westernization of the Arctic countries may influence the very particular cancer profile of these populations. Our objective was to investigate the development in cancer incidence from 1973 to 1997 in a large and well‐defined Inuit population in Greenland. Greenland is part of the Danish Kingdom, and population statistics covering both countries are available from the same registry resource. Data from the Danish Civil Registration System and from the Danish Cancer Registry were used to calculate age‐standardized cancer incidence rates for the periods 1973–1987 and 1988–1997 for persons born in Greenland. Using rates for Denmark, sex‐specific standardized incidence ratios (SIRs) for 1988–1997 were calculated. Furthermore, age‐ and sex‐specific incidence rates in the 2 periods were calculated for selected cancers. Total cancer incidence increased from 248.5 to 277.9 per 100,000 person‐years in men and from 269.4 to 302.2 per 100,000 person‐years in women. The incidence of lung, stomach, breast and colon cancer increased, whereas the incidence of cervical cancer decreased. Compared to the Caucasian population in Denmark, high SIRs were found for cancers of the nasopharynx, salivary gland, esophagus, stomach and cervix and low SIRs for testis, bladder, prostate, breast and hematologic cancers. Overall cancer incidence among Greenlandic Inuit is increasing as a result of increases in several cancers that are common in Western populations. A significant increase in the incidence of stomach cancer in both sexes, which contrasts global trends for this cancer, warrants further investigation.

The Inuit cancer pattern—The influence of migration

The Inuit cancer pattern is characterized by high frequencies of Epstein–Barr Virus (EBV)‐associated carcinomas of the nasopharynx and salivary glands. The reasons are unknown, but genetic and environmental factors are believed to be involved. Using data from the well‐defined Inuit population in Greenland we investigated whether migration to Denmark influenced their risk of cancer. Greenland is part of the Danish Kingdom, and population‐based registries cover both countries. Using rates for Denmark as reference, sex‐specific standardized incidence ratios (SIR) were calculated for Inuit who never lived in Denmark and for those who at least once were registered with a Danish address. During 1973–2003, we observed 3,567 cancers in a cohort of 77,888 persons. Of these, 862 among 26,214 Inuit ever living in Denmark, and 2,705 among 51,674 nonmigrating Inuit. High SIRs for cancers of the nasopharynx [31.7 (CI 22.0‐45.5)] and salivary glands [3.1 (CI 1.4–6.9)] observed among Inuit migrating to Denmark were comparable to those observed among Inuit never living in Denmark. Significant higher risk of cancer of the bladder, breast, prostate gland, skin, brain and stomach was observed among Inuit following migration to Denmark. The SIR was not generally influenced by duration of stay. The high risk of carcinoma of the nasopharynx and salivary glands observed in Inuit populations is maintained after migration to a low incidence area. This indicates that genetic factors or environmental factors acting early in life are etiologically important for these cancers.

Changing patterns of Hodgkin lymphoma incidence in Singapore

A bimodal age‐specific incidence pattern with a relatively high proportion of cases occurring in adolescents and young adults is a hallmark of Hodgkin lymphoma (HL) epidemiology in Western industrialized countries. The young adult incidence peak is believed to reflect the association between HL risk in young adults and an affluent childhood socioeconomic environment. However, the dynamic development of the young adult incidence peak following socioeconomic development implied by this interpretation has scarcely been demonstrated in a single population over time. We, therefore, analyzed incidence patterns of HL in Singapore between 1968 and 2004, during which time period a socioeconomic transition towards Western World lifestyles took place. As hypothesized a HL incidence peak emerged among adolescents and young adults in Singapore. Thus, in the age groups 15–19 and 20–24 years incidence rates increased annually by 7.0% (95% confidence interval 3.4%–10.7%) and 3.4% (0.1%–6.8%), respectively, in men and by 13.7% (9.1%–18.6%) and 12.2% (7.8–16.8%), respectively, in women between 1968 and 2004. However, the incidence peak remained considerably lower than what can be observed in young adults in the Western World. It remains to be determined to what extent the current lower incidence of HL in young Asian adults should be attributed to birth cohort phenomena, as would be suggested by continued increase in incidence, and to ethnic variation in HL susceptibility between Asian and non‐Asian populations, respectively.

Epstein-Barr virus-associated gastric carcinoma among patients with pernicious anemia

Approximately 9% of gastric carcinomas worldwide are associated with Epstein‐Barr virus (EBV), making it the most frequent EBV‐associated malignancy. Pernicious anemia, a condition with chronic gastritis and achlorhydria, is strongly associated with gastric carcinoma. Both chronic inflammation and the lack of stomach acid may influence the likelihood of EBV infection of the neoplastic gastric epithelium, but the prevalence of EBV‐associated gastric carcinoma among patients with pernicious anemia is unknown. Therefore, we conducted a Danish nationwide case–control study comparing gastric carcinoma patients with pernicious anemia (PA‐GC) with those without pernicious anemia (nonPA‐GC), frequency matched 1:2. Tumor tissues were reclassified by expert histopathologists blinded to pernicious anemia and EBV status. In total, 186 samples (55 PA‐GC and 131 nonPA‐GC) were identified. EBV‐associated gastric carcinoma (EBV‐GC) was more common among PA‐GC compared with nonPA‐GC, adjusted odds ratio (OR) = 2.53 (CI: 0.88; 7.14), p = 0.08, with further adjustment for lymphocytic infiltrate OR = 2.94 (0.99–8.67), p = 0.05. Gastric carcinomas with signet‐ring cell morphology were significantly less common in patients with PA‐GC compared with nonPA‐GC (OR = 0.05, CI 0.01; 0.24). Although these conditions are rare, we found suggestive evidence that EBV‐associated gastric carcinomas are more common among gastric carcinoma patients with pernicious anemia compared with those without.

Mannose-Binding Lectin Genotypes and Susceptibility to Epstein-Barr Virus Infection in Infancy

ABSTRACT In a cohort study of children <4 years of age in Greenland, mannose-binding lectin (MBL2) genotypes and Epstein-Barr virus (EBV) antibody levels were determined. EBV seropositivity was significantly lower and time to seroconversion increased in MBL-insufficient compared with MBL-sufficient children, indicating that MBL may be involved in primary EBV infection in infancy.

The Greenlandic research database: a population-based research resource.

Information on past exposures is often warranted in health studies in Greenland, as living conditions have changed markedly in this century. To provide a longitudinal population-based research tool with such information the Department of Epidemiology Research at Statens Serum Institut has established “The Greenlandic Research Database”, a comprehensive population-based database comprising data from Greenland from national registers, population-based longitudinal and cross-sectional studies and human biological samples from 1979 to the present day.