Variation in Nordic Work-Related Cancer Risks after Adjustment for Alcohol and Tobacco.

Background: Alcohol and tobacco strongly increases the risk of cancers of the tongue, mouth, pharynx, larynx, and oesophagus, and are also established risk factors for cancer of the liver, colon, and rectum. It is well documented that these habits are unequally distributed among occupational groups. Most occupational cohort studies lack information on these potentially important confounders, and may therefore be prone to bias. Aim: The aim of the study is to present Nordic standardized incidence ratios (SIRs) for alcohol and tobacco related cancer by occupation, after adjustment for alcohol and tobacco, and to compare to the unadjusted SIRs. Material and Methods: The study is based on the Nordic Occupational Cancer (NOCCA) database. We used confirmatory factor analysis models for simultaneous analysis of the cancer sites related to alcohol and tobacco, to obtain factors that allow for computation of adjusted expected numbers from the reference rates. We then calculated adjusted SIRs for the relevant cancer sites for each occupation. Results: For some occupations and cancers, the changes of risk estimates were striking, from significantly high to significantly low and vice versa. Among Nordic farmers, unadjusted SIRs for cancer of the mouth and oesophagus were 0.56 (95% confidence interval (CI) 0.51⁻0.61) and 0.67 (CI 0.63⁻0.70), respectively. After adjustment, estimates changed to 1.10 (CI 1.01⁻1.21) and 1.16 (CI 1.10⁻1.22). Unadjusted SIR for pharynx cancer among wood workers was 0.83 (CI 0.75⁻0.91), adjusted SIR was 1.14 (CI 1.03⁻1.25). For larynx cancer, results in the opposite direction were seen: unadjusted SIR for economically inactive was 1.38 (CI 1.31⁻1.46) while the adjusted SIR was 0.91 (CI 0.86⁻0.96). Conclusions: Adjustment for the latent indicators of alcohol and tobacco consumption changed risk estimates for several occupations, gave a less confounded description of risk, and may guide in the identification of true risk factors.

Adjustment for tobacco smoking and alcohol consumption by simultaneous analysis of several types of cancer.

PURPOSE: Tobacco smoking and alcohol consumption are risk factors for several types of cancer and may act as confounders in aetiological studies. Large register-based cohorts often lack data on tobacco and alcohol. We present a method for computing estimates of cancer risk adjusted for tobacco and alcohol without exposure information. METHODS: We propose the use of confirmatory factor analysis models for simultaneous analysis of several cancer sites related to tobacco and alcohol. In the analyses, the unobserved pattern of smoking habits and alcohol drinking is considered latent common factors. The models allow for different effects on each cancer site, and also for appropriate latent site-specific factors for subgroup variation. Results may be used to compute expected numbers of cancer from reference rates, adjusted for tobacco smoking and alcohol consumption. This method was applied to results from a large, published study of work-related cancer based on census data (1970) and 21 years of cancer incidence data from the national cancer registry. RESULTS: The results from our analysis were in accordance with recognised risks in selected occupational groups. The estimated relative effects from tobacco and alcohol on cancer risk were largely in line with results from Nordic reports. For lung cancer, adjustment for tobacco implied relative changes in SIR between a decrease from 1.16 to 0.72 (Fishermen), and an increase from 0.47 to 0.95 (Forestry workers). CONCLUSIONS: We consider the method useful for achieving less confounded estimates of cancer risk in large cohort studies with no available information on smoking and alcohol consumption.

Cervical cancer prevented by screening: Long-term incidence trends by morphology in Norway.

Both major morphologic types of cervical cancer, squamous cell carcinoma (SCC) and adenocarcinoma (AC), are causally related to persistent infection with high-risk human papillomavirus (hrHPV), but screening has primarily been effective at preventing SCC. We analysed incidence trends of cervical cancer in Norway stratified by morphologies over 55 years, and projected SCC incidence in the absence of screening by assessing the changes in the incidence rate of AC. The Cancer Registry of Norway was used to identify all 19,530 malignancies in the cervix diagnosed in the period 1956-2010. The majority of these (82.9%) were classified as SCCs, 10.5% as ACs and the remaining 6.6% were of other or undefined morphology. By joint-point analyses of a period of more than five decades, the average annual percentage change in the age-standardised incidence was -1.0 (95%CI: -2.1-0.1) for cervical SCC, 1.5 (95%CI:1.1-1.9) for cervical AC and -0.9 (95%CI: -1.4 to -0.3) for cervical cancers of other or undefined morphology. The projected age-standardised incidence rate of cervical SCC in Norway, assuming no screening, was 28.6 per 100,000 woman-years in 2010, which compared with the observed SCC rate of 7.3 corresponds to an estimated 74% reduction in SCC or a 68% reduction due to screening in the total cervical cancer burden. Cytology screening has impacted cervical cancer burden more than suggested by the overall observed cervical cancer incidence reduction since its peak in the mid-1970s. The simultaneous substantial increase in cervical adenocarcinoma in Norway is presumably indicative of an increase in exposure to HPV over time.

Results of delayed triage by HPV testing and cytology in the Norwegian Cervical Cancer Screening Programme.

BACKGROUND: High-risk human papilloma virus (hrHPV) testing was added to the cytology triage of women with equivocal screening smears in the Norwegian programme for cervical cancer screening in 2005. In this population-based observational before and after study we assessed the effect of changing the screening algorithm. MATERIAL AND METHODS: In periods before and after the change 75 852 and 66 616 women, respectively, were eligible for triage, i.e. they had smear results of unsatisfactory, atypical squamous cells of undetermined significance (ASC-US), or low-grade squamous intraepithelial lesion (LSIL) at routine screening. The triage was delayed as supplementary testing started six months after the initial screening. The groups were compared with respect to results of triage and later three-year cumulative incidence of cervical intraepithelial neoplasia grade 2 or worse (CIN2+). RESULTS: Before and after the change in the screening algorithm 5.2% (3964/75 852) and 8.1% (5417/66 616) of women, respectively, were referred to colposcopy. Among women referred to colposcopy cumulative incidence of CIN2+ (positive predictive value of referral) increased from 42.0% [95% confidence interval (CI): 40.3 - 43.7%] in the period with cytology only to 48.0% (95% CI 46.6 - 49.4%) after the start of HPV testing. For women recalled to ordinary screening the three-year cumulative incidence decreased from 2.7% (95% CI 2.5 - 2.9%) to 1.0% (95% CI 0.9 - 1.2%) during the same period. Among women with LSIL at routine screening and HPV testing in triage, 52.5% (1976/3766) were HPV positive. CONCLUSION: The new algorithm with HPV testing implemented in 2005 resulted in an increased rate of referral to colposcopy, but in a better risk stratification with respect to precancerous disease.

Mortality from cancer and other causes in commercial airline crews: a joint analysis of cohorts from 10 countries.

BACKGROUND: Commercial airline crew is one of the occupational groups with the highest exposures to ionising radiation. Crew members are also exposed to other physical risk factors and subject to potential disruption of circadian rhythms. METHODS: This study analyses mortality in a pooled cohort of 93 771 crew members from 10 countries. The cohort was followed for a mean of 21.7 years (2.0 million person-years), during which 5508 deaths occurred. RESULTS: The overall mortality was strongly reduced in male cockpit (SMR 0.56) and female cabin crews (SMR 0.73). The mortality from radiation-related cancers was also reduced in male cockpit crew (SMR 0.73), but not in female or male cabin crews (SMR 1.01 and 1.00, respectively). The mortality from female breast cancer (SMR 1.06), leukaemia and brain cancer was similar to that of the general population. The mortality from malignant melanoma was elevated, and significantly so in male cockpit crew (SMR 1.57). The mortality from cardiovascular diseases was strongly reduced (SMR 0.46). On the other hand, the mortality from aircraft accidents was exceedingly high (SMR 33.9), as was that from AIDS in male cabin crew (SMR 14.0). CONCLUSIONS: This large study with highly complete follow-up shows a reduced overall mortality in male cockpit and female cabin crews, an increased mortality of aircraft accidents and an increased mortality in malignant skin melanoma in cockpit crew. Further analysis after longer follow-up is recommended.

Overdiagnosis among women attending a population-based mammography screening program.

Increased incidence of ductal carcinoma in situ (DCIS) and invasive breast cancer (IBC) after introduction of organized screening has prompted debate about overdiagnosis. The aim was to examine the excess in incidence of DCIS and IBC during the screening period and the deficit after women left the program, and thereby to estimate the proportion of overdiagnosis. Women invited to the Norwegian Breast Cancer Screening Program were analyzed for DCIS or IBC during the period 1995-2009. Incidence rate ratios (IRRs) were calculated for attended vs. never attended women. The IRRs were adjusted by Mantel-Haenszel (MH) method and applied to a set of reference rates and a reference population to estimate the proportion of overdiagnosis during the women's lifespan after the age of 50 years. A total of 702,131 women were invited to the program. An excess of DCIS and IBC was observed among women who attended screening during the screening period; prevalently invited women aged 50-51 years had a MH IRR of 1.86 (95% CI 1.65-2.09) and subsequently invited women aged 52-69 years had a MH IRR of 1.56 (95% CI 1.45-1.68). In women aged 70-79 years, a deficit of 30% (MH IRR 0.70, 95% CI 0.62-0.80) was observed 1-10 years after they left the screening program. The estimated proportion of overdiagnosis varied from 10 to 20% depending on outcome and whether the women were invited or actually screened. The results highlight the need for individual data with longitudinal screening history and long-term follow-up as a basis for estimating overdiagnosis.

Cancer incidence among Nordic airline cabin crew.

Airline cabin crew are occupationally exposed to cosmic radiation and jet lag with potential disruption of circadian rhythms. This study assesses the influence of work-related factors in cancer incidence of cabin crew members. A cohort of 8,507 female and 1,559 male airline cabin attendants from Finland, Iceland, Norway and Sweden was followed for cancer incidence for a mean follow-up time of 23.6 years through the national cancer registries. Standardized incidence ratios (SIRs) were defined as ratios of observed and expected numbers of cases. A case-control study nested in the cohort (excluding Norway) was conducted to assess the relation between the estimated cumulative cosmic radiation dose and cumulative number of flights crossing six time zones (indicator of circadian disruption) and cancer risk. Analysis of breast cancer was adjusted for parity and age at first live birth. Among female cabin crew, a significantly increased incidence was observed for breast cancer [SIR 1.50, 95% confidence interval (95% CI) 1.32-1.69], leukemia (1.89, 95% CI 1.03-3.17) and skin melanoma (1.85, 95% CI 1.41-2.38). Among men, significant excesses in skin melanoma (3.00, 95% CI 1.78-4.74), nonmelanoma skin cancer (2.47, 95% CI 1.18-4.53), Kaposi sarcoma (86.0, 95% CI 41.2-158) and alcohol-related cancers (combined SIR 3.12, 95% CI 1.95-4.72) were found. This large study with complete follow-up and comprehensive cancer incidence data shows an increased incidence of several cancers, but according to the case-control analysis, excesses appear not to be related to the cosmic radiation or circadian disruptions from crossing multiple time zones.

Second events following ductal carcinoma in situ of the breast: a register-based cohort study.

The incidence of ductal carcinoma in situ (DCIS) of the breast has increased in recent decades, particularly, in counties offering mammography screening. The aims of the present study are to examine factors that may predict subsequent breast malignancy amongst patients with DCIS, and to compare the incidence of the subsequent malignancy and mortality with that of the general population. This population-based study includes all primary cases of pure DCIS diagnosed in Norway in the period 1993 to 2007 (N = 3167). The patients were followed to subsequent malignancy (DCIS or invasive cancer) or death. Risk estimates within 10 years of follow-up were calculated using Kaplan-Meier methods adjusting for competing risks, Cox regression models and Standard Incidence and Mortality Ratios. Patients with DCIS had a 11.2% risk of being diagnosed with a subsequent breast malignancy within 10 years (9.4% for invasive cancer), implying that they were five times as likely to be diagnosed with breast malignancy as the general female population in Norway. The risk was dependent on the treatment of the DCIS; patients treated with mastectomy and breast-conserving treatment had a 3.8 and 9.8% risk of ipsilateral invasive cancer within 10 years, respectively. Breast cancer mortality was 2.5% within 10 years of follow-up, a fourfold risk compared with the general population. Patients with DCIS have an increased risk of both subsequent breast malignancy and breast cancer death compared with women in the general population. Our results support previous knowledge of DCIS as a heterogeneous disease.

Factors associated with non-attendance, opportunistic attendance and reminded attendance to cervical screening in an organized screening program: a cross-sectional study of 12,058 Norwegian women.

BACKGROUND: Cervical cancer incidence and mortality may be reduced by organized screening. Participant compliance with the attendance recommendations of the screening program is necessary to achieve this. Knowledge about the predictors of compliance is needed in order to enhance screening attendance. METHODS: The Norwegian Co-ordinated Cervical Cancer Screening Program (NCCSP) registers all cervix cytology diagnoses in Norway and individually reminds women who have no registered smear for the past three years to make an appointment for screening. In the present study, a questionnaire on lifestyle and health was administered to a random sample of Norwegian women. The response rate was 68%. To address the predictors of screening attendance for the 12,058 women aged 25-45 who were eligible for this study, individual questionnaire data was linked to the cytology registry of the NCCSP. We distinguished between non-attendees, opportunistic attendees and reminded attendees to screening for a period of four years. Predictors of non-attendance versus attendance and reminded versus opportunistic attendance were established by multivariate logistic regression. RESULTS: Women who attended screening were more likely than non-attendees to report that they were aware of the recommended screening interval, a history of sexually transmitted infections and a history of hormonal contraceptive and condom use. Attendance was also positively associated with being married/cohabiting, being a non-smoker and giving birth. Women who attended after being reminded were more likely than opportunistic attendees to be aware of cervical cancer and the recommended screening interval, but less likely to report a history of sexually transmitted infections and hormonal contraceptive use. Moreover, the likelihood of reminded attendance increased with age. Educational level did not significantly affect the women's attendance status in the fully adjusted models. CONCLUSIONS: The likelihood of attendance in an organized screening program was higher among women who were aware of cervical screening, which suggests a potential for a higher attendance rate through improving the public knowledge of screening. Further, the lower awareness among opportunistic than reminded attendees suggests that physicians may inform their patients better when smears are taken at the physician's initiative.

Mortality among Norwegian doctors 1960-2000.

BACKGROUND: To study the mortality pattern of Norwegian doctors, people in human service occupations, other graduates and the general population during the period 1960-2000 by decade, gender and age. The total number of deaths in the study population was 1 583 559. METHODS: Census data from 1960, 1970, 1980 and 1990 relating to education were linked to data on 14 main causes of death from Statistics Norway, followed up for two five-year periods after census, and analyzed as stratified incidence-rate data. Mortality rate ratios were computed as combined Mantel-Haenzel estimates for each sex, adjusting for both age and period when appropriate. RESULTS: The doctors had a lower mortality rate than the general population for all causes of death except suicide. The mortality rate ratios for other graduates and human service occupations were 0.7-0.8 compared with the general population. However, doctors have a higher mortality than other graduates. The lowest estimates of mortality for doctors were for endocrine, nutritional and metabolic diseases, diseases in the urogenital tract or genitalia, digestive diseases and sudden death, for which the numbers were nearly half of those for the general population. The differences in mortality between doctors and the general population increased during the periods. CONCLUSIONS: Between 1960 and 2000 mortality for doctors converged towards the mortality for other university graduates and for people in human service occupations. However, there was a parallel increase in the gap between these groups and the rest of the population. The slightly higher mortality for doctors compared with mortality for other university graduates may be explained by the higher suicide rate for doctors.

Trends in incidence of ductal carcinoma in situ: the effect of a population-based screening programme.

BACKGROUND: The incidence of ductal carcinoma in situ (DCIS) has increased substantially in the western world in recent decades. The aim of this study was to investigate the incidence according to grade distribution, age, and implementation of a population-based screening programme. METHODS: Cases of primary pure DCIS (n = 3167) were obtained from the Cancer Registry of Norway. Poisson regression was used to estimate trends in incidence. RESULTS: Age-adjusted incidence of DCIS increased from 4 to 11 per 100, 000 women-years from 1993 to 2007, in parallel with the implementation of screening. Higher incidence was observed among prevalent (IRR 3.3) and subsequent (IRR 2.8) invited women compared with those not invited. The proportion of DCIS among breast malignancies increased throughout the period, most markedly in the age range of screening. CONCLUSION: The increased proportion of DCIS during the study period is probably due to improved diagnostics resulting from the implementation of population-based screening.

Improved breast cancer survival following introduction of an organized mammography screening program among both screened and unscreened women: a population-based cohort study.

INTRODUCTION: Mammography screening reduces breast cancer mortality through earlier diagnosis but may convey further benefit if screening is associated with optimized treatment through multidisciplinary medical care. In Norway, a national mammography screening program was introduced among women aged 50 to 69 years during 1995/6 to 2004. Also during this time, multidisciplinary breast cancer care units were implemented. METHODS: We constructed three cohorts of breast cancer patients: 1) the pre-program group comprising women diagnosed and treated before mammography screening began in their county of residence, 2) the post-program group comprising women diagnosed and treated through multidisciplinary breast cancer care units in their county but before they had been invited to mammography screening; and 3) the screening group comprising women diagnosed and treated after invitation to screening. We calculated Kaplan-Meier plots and multivariable Cox proportional hazard models. RESULTS: We studied 41,833 women with breast cancer. The nine-year breast cancer-specific survival rate was 0.66 (95%CI: 0.65 to 0.67) in the pre-program group; 0.72 (95%CI: 0.70 to 0.74) in the post-program group; and 0.84 (95%CI: 0.80 to 0.88) in the screening group. In multivariable analyses, the risk of death from breast cancer was 14% lower in the post-program group than in the pre-program group (hazard ratio 0.86; (95%CI: 0.78 to 0.95, P = 0.003)). CONCLUSIONS: After nine years follow-up, at least 33% of the improved survival is attributable to improved breast cancer management through multidisciplinary medical care.

Mortality and causes of death after hospital-treated self-poisoning in Oslo: a 20-year follow-up.

INTRODUCTION: Self-poisoning is a risk factor for premature death and for suicide, but for how long? The aims were to examine the mortality rate, causes of death, and risk factors for mortality and suicide during 20 years. METHOD: Prospective cohort study including all patients discharged after self-poisoning from all medical departments in Oslo in 1980 (n = 946, 51 % females, median age 31 years). Standardized mortality ratios (SMRs) and Cox regression analysis were used. RESULTS: During follow-up, 355 (37.5%) of the patients died, SMR 4.6 (95% CI, 4.2-5.1). After 15 years, the SMR was still 3.3 (95% C.I., 2.5-4.2). Sixty-seven (7.1%) committed suicide, SMR 26.7 (95% CI, 21.0-33.9). The risk of death from all causes was significantly higher. Unspecific risk factors for death were found. A suicidal motive was the only risk factor for suicide. CONCLUSION: The mortality rate implies a poor prognosis in this patient group.

[Cervical cancer after 10 years of nationally coordinated screening]. / Livmorhalskreft etter ti års offentlig koordinert screening.

BACKGROUND: A cervical cancer screening programme has been operating on a national level since 1995. Women aged 25-69 years who have not had a Pap smear in the previous 3-year period, are recommended by letter to contact a doctor and have a smear taken. The aims of the programme are a more rational use of tests and to decrease the incidence and mortality of the disease. MATERIAL AND METHODS: Trends in incidence and mortality of cervical cancer are studied by data from the national cancer registry, which also collects data on individual smears. RESULTS: From the period 1990-94 to the period 2000-04 the age-adjusted incidence rate per 1,000, 000 person-years decreased from 127 to 95, the corresponding rate for squamous carcinomas decreased from 102 to 70. The age-adjusted mortality rate decreased from 38 to 25. Number of tests decreased from 542,666 in 1994 to 486 118 in 2004. The proportion of women aged 25-69 years who had a test taken during the last four years, increased from 72.4% in 1995 to 78.3% in 2004. INTERPRETATION: Implementation of a nationally coordinated cervical cancer screening programme has contributed to a favourable development of the disease (lower incidence and mortality) and a more rational use of tests. Continued efforts are needed to achieve the goals of the programme.

A 20-year prospective study of mortality and causes of death among hospitalized opioid addicts in Oslo.

BACKGROUND: To study mortality rate and causes of death among all hospitalized opioid addicts treated for self-poisoning or admitted for voluntary detoxification in Oslo between 1980 and 1981, and to compare their mortality to that of the general population. METHODS: A prospective cohort study was conducted on 185 opioid addicts from all medical departments in Oslo who were treated for either self-poisoning (n = 93, 1980), voluntary detoxification (n = 75, 1980/1981) or both (n = 17). Their median age was 24 years; with a range from 16 to 41, and 53% were males. All deaths that had occurred by the end of 2000 were identified from the Central Population Register. Causes of death were obtained from Statistics Norway. Standardized mortality ratios (SMRs) were computed for mortality, in general, and in particular, for different causes of death. RESULTS: During a period of 20 years, 70 opioid addicts died (37.8%), with a standardized mortality ratio (SMR) equal to 23.6 (95% CI, 18.7-29.9). The SMR remained high during the whole period, ranging from 32.4 in the first five-year period, to 13.4 in the last five-year period. There were no significant differences in SMR between self-poisonings and those admitted for voluntarily detoxification. The registered causes of death were accidents (11.4%), suicide (7.1%), cancer (4.3%), cardiovascular disease (2.9%), other violent deaths (2.9%), other diseases (71.4%). Among the 50 deaths classified as other diseases, the category "drug dependence" was listed in the vast majority of cases (37 deaths, 52.9% of the total). SMRs increased significantly for all causes of death, with the other diseases group having the highest SMR; 65.8 (95% CI, 49.9-86.9). The SMR was 5.4 (95% CI, 1.3-21.5) for cardiovascular diseases, and 4.3 (95% CI, 1.4-13.5) for cancer. The SMR was 13.2 (95% CI, 6.6-26.4) for accidents, 10.7 (95% CI, 4.5-25.8) for suicides, and 28.6 (95% CI, 7.1-114.4) for other violent deaths. CONCLUSION: The risk of death among opioid addicts was significantly higher for all causes of death compared with the general population, implying a poor prognosis over a 20-year period for this young patient group.

Impact of respiratory symptoms on lung cancer: 30-year follow-up of an urban population.

We investigated the relationship between respiratory symptoms reported at one time and incidence of lung cancer the subsequent 30 years in an urban Norwegian population. A cohort of 19,998 persons, aged 15-70 years living in Oslo, was randomly selected for a respiratory survey in 1972. The response-rate was 89% and 17,670 respondents were followed up. The relationship between respiratory symptoms and lung cancer incidence was investigated separately for each symptom group, symptom score and sex, with adjustment for age, smoking habits and occupational exposure. Lung cancer developed in 352 persons (228 men and 124 women) during follow up. We found a significant positive association between the incidence of lung cancer and cough symptoms in both sexes, asthma-like symptoms among women and dyspnoea when walking uphill among men. The relative risk for lung cancer increased with the number of symptoms reported at baseline and was strongest the first decade and decreased with duration of follow up. This association was more pronounced for non-small cell lung cancer than for small cell lung cancer.

Respiratory symptoms and long-term cardiovascular mortality.

BACKGROUND: Our aim was to investigate the association between respiratory symptoms and mortality from ischaemic heart disease (IHD) and stroke in a population during 30 years follow-up. METHODS: In 1972, 19998 persons aged 15-70 years, living in Oslo, were selected for a respiratory survey (response 89%). Respiratory symptoms were divided into four groups and given a score. The association between respiratory symptoms and mortality from IHD and stroke were investigated separately for men and women, with adjustment for age, occupational exposure to air pollution and smoking habits. RESULTS: IHD accounted for 1572 and stroke for 653 of all deaths. The adjusted hazard ratio (HR) for mortality from IHD in men varied from 1.3 (95% confidence interval, 1.1-1.5) to 3.0 (2.3-3.8) and in women from 1.2 (1.0-1.5) to 1.9 (1.4-2.5) for cough symptoms and severe dyspnoea, respectively. Symptom score predicted death from IHD, in a dose-response manner. The HR for mortality from stroke varied from 1.0 to 2.3 in men and from 1.1 to 1.5 in women for the symptom groups, but was significant only among men reporting severe dyspnoea and among women reporting moderate dyspnoea. For all respiratory symptoms, the excess risk for cardiovascular mortality decreased during follow-up, but IHD-mortality was still significantly increased the last decade. CONCLUSION: We found a significant, positive association between respiratory symptoms and 30-year mortality from IHD. The positive association was weaker between respiratory symptoms and long-term mortality from stroke.

Mortality in the Sami population of North Norway, 1970-98.

AIMS: The pattern of mortality among many groups of indigenous people has been shown to be disadvantageous in comparison with the general population. Knowledge regarding causes of death among the Sami population in the northern part of Norway is limited. The Sami constitute an ethnic minority whose lifestyle diverges from that of the rest of the population. METHODS: A cohort of 19,801 persons of Sami origin was followed up to evaluate specific causes of mortality during the period 1970-98. Standardized mortality rates (SMR) were calculated using the rural population of the three Norwegian counties included in the study as a reference population. RESULTS: Among Sami, 5,955 total deaths were observed, as opposed to 5,537 expected (SMR = 1.08). For both Sami women and men a significantly higher SMR for cerebrovascular diseases was found, which was more pronounced for women. For Sami men, an excess SMR for violent death was observed (SMR 1.32, 95% confidence interval (CI) 1.20-1.46); this was highest among Sami men living in a reindeer-breeding family. For both genders, mortality from all malignant neoplasms combined was lower than in the reference population. SMRs were 0.86 (95% CI 0.79-0.94) and 0.89 (95% CI 0.80-0.99) for men and women, respectively. Low SMRs were also observed for chronic liver diseases, 0.18 (95% CI 0.02-0.63) and 0.12 (95% CI 0.00-0.68) for Sami men and women, respectively. To be a member of a reindeer breeding household appeared to offer protection from mortality caused by circulatory system diseases in men, especially mortality from ischaemic heart disease. CONCLUSIONS: The total mortality in the North Norway Sami population, an ethnic minority in Norway, was slightly higher when compared with a regional reference population. The differences observed when evaluating mortality by diagnosis might be due to lifestyle, diet, psychosocial, and/or genetic factors.