Log-linear models for cancer risk among migrants

Cancer risks in Nairobi (2000-2014) by ethnic group

We investigated the ethnic differences in the risk of several cancers in the population of Nairobi, Kenya, using data from the Nairobi Cancer Registry. The registry records the variable "Tribe" for each case, a categorisation that includes, as well as 22 tribal groups, categories for Kenyans of European and of Asian origin, and non-Kenyan Africans. Tribes included in the final analysis were Kikuyu, Kamba, Kisii, Kalenjin, Luo, Luhya, Somalis, Asians, non-Kenyans, Caucasians, Other tribes and unknown. The largest group was taken as the reference category for the calculation of odds ratios; this was African Kenyans (for comparisons by race), and Kikuyus (the tribe with the largest numbers of cancer registrations (38% of the total)) for comparisons between the Kenyan tribes. P-values are obtained from the Wald test. Cancers that were more common among the white population than in black Kenyans were skin cancers and cancers of the bladder, while cancers that are more common in Kenyan Asians include colorectal, lung, breast, ovary, corpus uteri and non-Hodgkin lymphoma. Cancers that were less common among Asians and Caucasians were oesophagus, stomach and cervix cancer. Within the African population, there were marked differences in cancer risk by tribe. Among the tribes of Bantu ethnicity, the Kamba had higher risks of melanoma, Kaposi sarcoma, liver and cervix cancer, and lower risks of oesophagus, stomach, corpus uteri and nervous system cancers. Luo and Luhya had much higher odds of Kaposi sarcoma and Burkitt lymphoma.

Black-white differences in cancer risk in Harare, Zimbabwe, during 1991-2010

Data from 20 years of cancer registration in Harare (Zimbabwe) are used to investigate the risk of cancer in the white population of the city (of European origin), relative to that in blacks (of African origin). In the absence of information on the respective populations-at-risk, we calculated odds of each major cancer among all cancers, and took the odds ratios of whites to blacks. Some major differences reflect obvious phenotypic differences (the very high incidence of skin cancer-melanoma and nonmelanoma--in the white population), whereas others (high rates of liver cancer, Kaposi sarcoma and conjunctival cancers in blacks) are the result of differences in exposure to infectious agents. Of particular interest are cancers related to lifestyle factors, and how the differences in risk are changing over time, as a result of evolving lifestyles. Thus, the high risk of cancers of the esophagus and cervix uteri in blacks (relative to whites) and colorectal cancers in whites show little change over time. Conversely, the odds of breast cancer, on average four times higher in whites than blacks, has shown a significant decrease in the differential over time. Cancer of the prostate, with the odds initially (1991-1997) 15% higher in whites had become 33% higher in blacks by 2004-2010.

Spatial clusters of autism births and diagnoses point to contextual drivers of increased prevalence

Autism prevalence has risen dramatically over the past two decades in California. Although often suggested to have been crucial to the rise of autism, environmental and social contextual drivers of diagnosis have not been extensively examined. Identifying the spatial patterning of autism cases at birth and at diagnosis can help clarify which contextual drivers are affecting autism's rising prevalence. Children with autism not co-morbid with mental retardation served by the California Department of Developmental Services during the period 1992-2005 were matched to California's Birth Master Files. We search for spatial clusters of autism at time of birth and at time of diagnosis using a spatial scan approach that controls for key individual-level risk factors. We then test whether indicators of neighborhood-level diagnostic resources are associated with the diagnostic clusters and assess the extent of clustering by autism symptom severity through a multivariate scan. Finally, we test whether children who move into neighborhoods with higher levels of resources are more likely to receive an autism diagnosis relative to those who do not move with regard to resources. Significant birth and diagnostic clusters of autism are observed independent of key individual-level risk factors. While the clusters overlap, there is a strong positive association between the diagnostic clusters and neighborhood-level diagnostic resources. In addition, children with autism who are higher functioning are more likely to be diagnosed within a cluster than children with autism who are lower functioning. Most importantly, children who move into a neighborhood with more diagnostic resources than their previous residence are more likely to subsequently receive an autism diagnosis than children whose neighborhood resources do not change. We identify birth and diagnostic clusters of autism in California that are independent of individual-level autism risk factors. Our findings implicate a causal relationship between neighborhood-level diagnostic resources and spatial patterns of autism incidence but do not rule out the possibility that environmental toxicants have also contributed to autism risk.

MC1R genotype may modify the effect of sun exposure on melanoma risk in the GEM study

We investigated whether MC1R genotype modifies the effect of sun exposure on melanoma risk in 1,018 cases with multiple melanomas (MPM) and 1,875 controls with one melanoma (SPM). There was some suggestion that MC1R genotype modified the effect of beach and water activities on MPM risk: ORs were 1.94 (95% CI 1.40-2.70) for any activities for no R variants and 1.39 (95% CI 1.05-1.84) with R variants (R151C, R160W, D294H, and D84E) (p for interaction 0.08). MC1R modification of sun exposure effects appeared most evident for MPM of the head and neck: for early life ambient UV, the OR was 4.23 (95% CI 1.76-10.20) with no R and 1.04 (95% CI 0.40-2.68) with R (p for interaction = 0.01; p for three-way interaction = 0.01). Phenotype modified the effect of sun exposure and MPM in a similar manner. We conclude that MC1R and pigmentary phenotype may modify the effects of sun exposure on melanoma risk on more continuously sun-exposed skin. Possible explanations include that risk may saturate with higher sun sensitivity for melanomas on continuously sun-exposed sites but continue to increase as sun exposure increases with lower sun sensitivity, or that sun-sensitive people adapt their behavior by increasing sun protection when exposed.

Cancer mortality in migrants from the British Isles and continental Europe to New South Wales, Australia, 1975-1995

Routinely collected data for New South Wales were used to analyse cancer mortality in migrants from the British Isles, southern Europe and eastern Europe according to duration of residence in Australia. A case-control approach compared deaths from cancer at one site with deaths from all other cancers, adjusting for age, sex and calendar period. Compared with the Australia-born, migrants had a significantly lower risk of dying from cancers of the mouth/pharynx and prostate (migrants from each region), colon/rectum (from the British Isles and southern Europe) and lung (female southern European migrants), evident from the time of migration and maintained for 30 years after migration. Whereas a deficit of deaths from colorectal cancer remained in migrants from southern Europe, a clear gradient of increasing risk with duration of stay in Australia was apparent. A similar trend was seen with respect to kidney cancer in southern European migrants. Persistent excess risks of death from stomach cancer were seen in all migrant groups, from lung cancer in British migrants and from liver cancer in southern and eastern European migrants. Although the risk of death from breast cancer increased significantly with duration in Australia in southern European migrants, the increase was not monotonic, as the relative risk in the first 10 years after migration was almost the same as that after more than 30 years. The pattern of risk for cancers of the prostate and mouth/pharynx suggests some protective role for inheritance or maintained cultural factors.

Cancer mortality in East and Southeast Asian migrants to New South Wales, Australia, 1975-1995

Routinely collected data for New South Wales were used to analyse cancer mortality in migrants born in East or Southeast Asia according to duration of residence in Australia. A case-control approach compared deaths from cancer at particular sites with deaths from all other cancers, adjusting for age, sex and calendar period. Compared with the Australian-born, these Asian migrants had a 30-fold higher risk of dying from nasopharyngeal cancer in the first 2 decades of residence, falling to ninefold after 30 years, and for deaths from liver cancer, a 12-fold risk in the first 2 decades, falling to threefold after 30 years. The initial lower risk from colorectal, breast or prostate cancers later converged towards the Australian-born level, the change being apparent in the third decade after migration. The relative risk of dying from lung cancer among these Asian migrants was above unity for each category of duration of stay for women, but at or below unity for men, with no trend in risk over time. An environmental or lifestyle influence for nasopharyngeal and liver cancers is suggested as well as for cancers of colon/rectum, breast and prostate.

Risk of cancer in migrants and their descendants in Israel: I. Leukaemias and lymphomas

Cancer registrations among young individuals (under age 30 years) for the 30-year period 1960-1989 were used to investigate the risk of leukaemia and lymphoma in migrants to Israel, and in their offspring, relative to Israel-born individuals with Israel-born parents. Relative risks by the father's continent of origin, and odds ratios by continent of origin of mother or both parents, adjusted for age, sex and period, were estimated. The leukaemias showed little variation in risk by birthplace, and no change between generations. For non-Hodgkin lymphoma, however, there were quite large differences in incidence, with relatively high rates in migrants from Asia and Africa. These persisted to some degree into the second generation, suggesting that inherited susceptibility may underlie some of the variation.

Risk of cancer in migrants and their descendants in Israel: II. Carcinomas and germ-cell tumours

Cancer registrations among young individuals (under age 30 years) for a 30-year period (1960-1989) were used to investigate the risk of cancer in migrants to Israel, and in their offspring, relative to Israel-born individuals with Israel-born parents. Relative risks of testis and ovarian cancer (germ cell tumours and carcinomas), melanoma, and carcinomas of nasopharynx, colorectum, breast, cervix and thyroid were calculated according to father's birthplace, and odds ratios for birthplace of mother, or of both parents. The estimates were adjusted for the effects of age, sex and time period. For 3 cancers, i.e., testis cancer, nasopharyngeal carcinoma and melanoma, there were quite large differences in incidence, which persisted to some degree into the second generation, suggesting that inherited susceptibility may underlie some of the variation. For ovarian, colorectal, cervical and thyroid cancers, differences in risk between the migrant groups had largely disappeared in their offspring, suggesting that environmental exposures, which were modified by migration, are the major causative factors.

High risk of lymphomas in children of Asian origin: ethnicity or confounding by socioeconomic status?

To examine the role of ethnic origin as a risk factor for paediatric lymphoma, a cancer registry-based analysis was undertaken in Yorkshire, UK. Children of Asian ethnic origin were found to have an odds ratio for lymphomas of 1.60 (CI 0.98-2.62), after adjusting for age and sex. After adjusting also for 'super profile group' as an indicator of socioeconomic status, the estimate became 1.99 (CI 1.08-3.68). Hodgkin's disease and non-Hodgkin's lymphomas were analysed separately with similar results. Super profile group is an area-based measure and may not reflect the individual variation in living standards, especially among the Asian immigrants. Our results indicate that socioeconomic status does not confound the relationship between lymphomas and ethnic origin. However, there is a need for studies of ethnicity that include indicators of individual living standards or socioeconomic status.

Studies of cancer in migrants: rationale and methodology

Migrant populations comprise substantial numbers of individuals who have undergone a change in their environment, sociocultural and physical. The corresponding changes in risk for different cancers have, therefore, been widely used to infer the relative importance of environmental factors versus inherited predisposition in cancer aetiology. The uncontrolled experiment of migration also provides an indication of the possible effects of certain preventive interventions at the population level--especially with respect to diet. In the past, there has been a surprising lack of attention to analytical methods for migrant data, and we review the epidemiological methods available to best bring out the relevant differences in risk. The major sources of bias which confuse interpretation are also described. Migrant studies are classified into four groups, in a hierarchy corresponding to the amount of information which they can provide, and examples of each type are provided.

Increased asthma hospitalizations among registered Indian children and adults in Saskatchewan, 1970-1989

We investigated asthma morbidity in children and adults among Registered Indians in Saskatchewan using hospitalization data for 1970-1989. In Registered Indians, significant increases were observed in the asthma hospitalization rates from 1979 to 1989 in boys and girls under 4 years, boys aged 5-14 years, and female adults aged 15-34 years respectively. In children under 4 years, the asthma hospitalization rates increased from 12.7 per 1000 in 1979 to 21.7 per 1000 in 1989. Asthma hospitalizations were higher among Indian boys than girls in the age group 0-4 years but this was reversed in the age groups 15-34 and 35-64 years. When compared with other Saskatchewan populations, the Indian population in age groups 0-4 and 35-64 years had significantly increased risk for hospitalization for asthma. Even though asthma was reported to be rare among Indians before 1975, we observed increases in asthma morbidity in recent years among Indian children and young adults.

Cervical cancer: incidence and survival in migrants within Spain

STUDY OBJECTIVE

This study examined the incidence of cervical cancer and survival rates according to migrant experience of women from different regions of Spain to Girona, Catalonia (Spain).

DESIGN

Using data from the population based cancer registry of Girona for the period 1980-89, crude and age adjusted incidence rates were calculated for local-born and first generation migrants from other Spanish regions. The age standardised rate ratio (SRR) was calculated and Cox's regression model was used to adjust survival according to migrant status for age and stage at diagnosis.

MAIN RESULTS

The incidence of cervical cancer was significantly higher in first generation Spanish migrants compared with locally born women (SRR: 2.02; 95% CI 1.40:2.92). The stage at diagnosis was more advanced among migrants. Survival probability was significantly associated with stage at diagnosis, but age and region of birth were not.

CONCLUSIONS

Migrants from the southern Spanish regions show a twofold excess in the incidence of cervical cancer compared with the Girona-born female population. Cases of cervical cancer in migrants are diagnosed at a more advanced stage and as a consequence have a poorer prognosis.

Cancer mortality in Italian migrants and their offspring in Canada

Studies on the offspring of migrants provide important information on the contribution of environmental and genetic factors in the etiology of various cancers. The aim of the present study is to analyze the cancer risk in Italian-migrants (Canadian residents born in Italy) and their offspring compared with the host population. Odds ratios (OR) and 95 percent confidence intervals (CI) by site and birthplace categories (migrants, pure and mixed Italian-parentage Canadians) were calculated by means of a case-control study using the 'other cancer deaths' as controls and taking the host population as the reference category. The study shows that Italian migrants retain a significantly low risk for a series of cancers: colon (OR = 0.9 in males and 0.7 in females); lung (OR = 0.8 in males and 0.5 in females); and breast (OR = 0.9). For all of these sites, risks in the offspring of Italian migrants were not different from those of the host population, with some differences between the genders with respect to cancer of the colon. Stomach cancer presents a significantly high rate in migrants (OR = 1.9 in males and 2.4 in females), consistent with the population of Italy; in their offspring, risks are similar to those in the host population. The risk of cancer in the offspring of migrants is, for many sites, intermediate between the host population and the Canadian residents born in Italy. This finding possibly is related to the larger integration of the offspring than their parents in the cultural and social environment of the host population.

Cancer mortality among Chinese and South-East Asian migrants in France

The cancer risk in migrants from China and South-east Asia (Vietnam, Laos and Cambodia) resident in France has been compared to that observed in the local-born population, using mortality data from the period 1979-1985 and population data from the 1982 French census. Risks were adjusted for important confounding factors such as social standing and area of residence. Compared to local-born, South-east Asian migrants of one sex or both sexes combined have higher risks of cancer of the nasopharynx, stomach, liver, gallbladder, lung (in females only), and cervix. On the other hand, South-east Asian migrants have lower risks of cancer of the oral cavity, other pharynx, colon, rectum, larynx, lung (among males only), bladder, nervous system, breast and prostate. Within this group, the risks are quite similar for Vietnamese, Laotians and Cambodians. Results for Chinese-born migrants are quite similar, for most sites, to those found among South-east Asian migrants, although, because of smaller numbers, few of the estimates are statistically significant. These results are consistent with other studies on Chinese migrants around the world, and with the 3 other previous studies on Vietnamese migrants, in England and Wales, Los Angeles and Australia.

Education and mortality from cancer in São Paulo, Brazil

This study investigated social class differentials in cancer mortality in São Paulo county, Brazil, for the period 1978 to 1982. A measure of socioeconomic status based on education was used, and cancer risk by level of education was estimated by a case-control approach in which other cancers were considered as controls. For most cancers, the socioeconomic differences in risk were similar to those found in western Europe and North America. For lung cancer, however, the highest risk was observed in men and women with the most education. Other cancers related to tobacco--cancer of the larynx, pharynx, and esophagus--showed a negative association with education. The differences between social classes in consumption habits of alcohol and maté and the use of black tobacco are probably responsible for these contrasting patterns. For breast and cervix uteri cancer the social class patterns were similar to those found in developed countries--a positive relationship for breast and a negative one for cervix uteri cancer. The magnitude of the differences observed between social classes for these cancers was frequently greater in South America than in the United States or western Europe.

The incidence of colon, breast and prostate cancer in Italian migrants to Victoria, Australia

The incidence of cancers of the colon, breast and prostate in Australian and Italian born residents of Victoria, Australia were compared with the incidence of these cancers in Italy. Italian migrants' rates were between those of the Australian born and those from Italian cancer registries. Italian migrants' rates for colon cancer (males 23.1 and females 15.8 per 100,000) differed from rates in Ragusa (males 12.1 and females 10.4 per 100,000) but not from rates in Parma or Varese. The migrants' breast cancer rate was similar to the rate in Ragusans (48.7 vs 46.7) and their prostate cancer rate of 27.3 was higher than all Italian registries. Modelling identified that Italian migrants' rates by age were intermediate to Australian and Italian rates, but indistinguishable from cancer rates in Ragusa, except for colon cancer which demonstrated an interaction with age.

Cancer mortality in African and Caribbean migrants to England and Wales

Cancer mortality during 1970-85 of immigrants from East and West Africa and the Caribbean to England and Wales is described. Overall cancer mortality was raised in West African males (RR 1.38, 95% CI 1.25-1.54), and non-significantly raised in West African females (RR 1.14, 0.96-1.37) compared to mortality in the England and Wales-born population. Much of the increased risk was due to very high rates of liver cancer in males (RR 31.6, 23.8-41.9), but rates were also raised for a wide range of other cancers in each sex. Only lung and brain cancer had significantly decreased mortality. In East Africans, overall cancer mortality was low in males (RR 0.63, 0.56-0.70), and in females (RR 0.80, 0.72-0.89). Mortality was significantly low for cancers of the stomach, pancreas and testis, and Hodgkin's disease in males, for cervical cancer in females, and for lung cancer and melanoma in both sexes. Cancer sites with significantly raised mortality included oropharyngeal cancer, leukaemia, and multiple myeloma in both sexes. In Caribbean immigrants overall cancer rates were significantly low in males (RR 0.71, 0.68-0.74) and in females (RR 0.76, 0.73-0.80). Mortality was significantly low for many cancers including colorectal, lung, testis and brain cancers. Mortality was significantly raised only for cancer of the prostate in males, of the placenta in females, and of the liver, non-Hodgkin's lymphoma and multiple myeloma in both sexes. Overall, mortality was high from prostatic cancer and liver cancer, and was low from brain cancer, in predominantly ethnic African immigrant groups. Both East and West African immigrants had raised rates of leukaemia. All of the migrant groups had high rates of multiple myeloma and low rates of testicular, ovarian and lung cancer. Genetic and environmental factors that may contribute to these patterns are discussed.

Cancer in migrants to Argentina

Mortality rates from different cancers in migrants to Argentina from 11 individual countries and 6 groups of countries were compared with those in the Argentina-born population and in their countries of origin. Almost all countries of origin had higher mortality rates from gastric cancer than Argentina, but the risk declines in migrants, and for European migrants becomes similar to that of the Argentina-born. In contrast, mortality from oesophageal cancer is significantly lower in European countries than in Argentina. For cancer of the colon and breast, most countries have lower mortality rates than the Argentina-born, the exceptions being Uruguay and Germany, and migrants demonstrate a convergence of risk towards that of Argentina-born. These results suggest that migrants to Argentina undergo changes in some environmental exposure, probably dietary, which give rise to substantial alterations in cancer risk within their lifespan.

Childhood cancer and ethnic group in Britain: a United Kingdom children's Cancer Study Group (UKCCSG) study

We present here the results of the largest study of childhood cancer and ethnic group in Britain, based on 7,658 children treated at paediatric oncology centres throughout the country. Incidence rates could not be calculated and so relative frequencies were analysed by the log-linear modelling method of Kaldor et al. (1990) with allowance made for regional variations in the ages and diagnostic groups of the children included in the study. Children of Asian (Indian sub-continent) and West Indian ethnic origin had similar patterns of incidence for acute lymphoblastic leukaemia to White Caucasians. There was a significant excess of Hodgkin's disease among Asian children compared with Caucasians with an estimated relative risk (RR) of 2.09; this excess was greatest in the 0-4 age group (RR = 6.67). There were significant deficits of Wilms' tumour and rhabdomyosarcoma among Asian children, each with a frequency around half that among Caucasians, whereas West Indians had a significant excess of Wilms' tumour (RR = 2.55). Asian and West Indian children each had a non-significant twofold RR for unilateral retinoblastoma. The results suggest that the incidence of childhood acute lymphoblastic leukaemia is associated with environmental determinants in the country of residence which are most likely to relate to lifestyle factors. The occurrence of retinoblastoma, Wilms' tumour and Hodgkin's disease in early childhood is apparently related more to ethnicity than to geographical location and may reflect genetic factors or environmental exposures specific to the lifestyle of particular ethnic groups.

Cancer in Italian migrants

Migration of Italians to other parts of the world has a long history and has involved very large numbers of individuals. The study of the health consequences of this migration is made possible by the availability of statistics on mortality and morbidity, both in Italy and in the host countries, and of social and economic information on the various Italian communities abroad. The results of the major studies are reviewed, comparing the rates in immigrants with those in the host countries and in Italy. The differences in cancer rates between Italian and local-born populations--for stomach cancer in both sexes, and for cancer of the colon, lung, and breast in females, and for prostate cancer--are consistent with the direction of differences between rates in Italy and those in the host countries. For colon and rectum cancer in males, there are unexpected findings in most of the United States' studies. Analysis by duration of residence shows changes in the risk for several sites in males, but not in females, according to length of stay in the host country. This finding possibly reflects greater stability of habits and lifestyle in females compared to males.

Cancer in Jewish migrants to Israel

Data on the incidence of 15 cancers in the Jewish population of Israel from the period 1961-1981 have been studied with emphasis on the risk of disease in relation to birthplace, calendar time, and duration of residence in Israel. The results show wide variations in incidence by birthplace, from less than 2-fold for pancreatic cancer to a 40-fold difference for oesophageal cancer in females; the reasons for these are often little understood. The potential importance of environmental agents in aetiology for different migrant groups is discussed in relation to the size and rapidity of changes in risk related to the duration of residence in Israel.