Vilhjálmur Rafnsson

Incidence of cancer among Nordic airline pilots over five decades: occupational cohort study

Abstract Objective: To assess the incidence of cancer among male airline pilots in the Nordic countries, with special reference to risk related to cosmic radiation. Design: Retrospective cohort study, with follow up of cancer incidence through the national cancer registries. Setting: Denmark, Finland, Iceland, Norway, and Sweden. Participants: 10 032 male airline pilots, with an average follow up of 17 years. Main outcome measures: Standardised incidence ratios, with expected numbers based on national cancer incidence rates; dose-response analysis using Poisson regression. Results: 466 cases of cancer were diagnosed compared with 456 expected. The only significantly increased standardised incidence ratios were for skin cancer: melanoma 2.3 (95% confidence interval 1.7 to 3.0), non-melanoma 2.1 (1.7 to 2.8), basal cell carcinoma 2.5 (1.9 to 3.2). The relative risk of skin cancers increased with the estimated radiation dose. The relative risk of prostate cancer increased with increasing number of flight hours in long distance aircraft. Conclusions: This study does not indicate a marked increase in cancer risk attributable to cosmic radiation, although some influence of cosmic radiation on skin cancer cannot be entirely excluded. The suggestion of an association between number of long distance flights (possibly related to circadian hormonal disturbances) and prostate cancer needs to be confirmed.

Incidence of cancer among commercial airline pilots

OBJECTIVES To describe the cancer pattern in a cohort of commercial pilots by follow up through the Icelandic Cancer Registry. METHODS This is a retrospective cohort study of 458 pilots with emphasis on subcohort working for an airline operating on international routes. A computerised file of the cohort was record linked to the Cancer Registry by making use of personal identification numbers. Expected numbers of cancer cases were calculated on the basis of number of person-years and incidences of cancer at specific sites for men provided by the Cancer Registry. Numbers of separate analyses were made according to different exposure variables. RESULTS The standardised incidence ratio (SIR) for all cancers was 0.97 (95% confidence interval (95% CI) 0.62 to 1.46) in the total cohort and 1.16 (95% CI 0.70 to 1.81) among those operating on international routes. The SIR for malignant melanoma of the skin was 10.20, 95% CI 3.29 to 23.81 in the total cohort and 15.63, 95% CI 5.04 to 36.46 in the restricted cohort. Analyses according to number of block-hours and radiation dose showed that malignant melanomas were found in the subgroups with highest exposure estimates, the SIRs were 13.04 and 28.57 respectively. The SIR was 25.00 for malignant melanoma among those who had been flying over five time zones. CONCLUSIONS The study shows a high occurrence of malignant melanoma among pilots. It is open to discussion what role exposure of cosmic radiation, numbers of block-hours flown, or lifestyle factors—such as possible excessive sunbathing—play in the aetiology of cancer among pilots. This calls for further and more powerful studies. The excess of malignant melanoma among those flying over five time zones suggests that the importance of disturbance of the circadian rhythm should be taken into consideration in future studies.

Cause-Specific Mortality in Adults with Unprovoked Seizures

Purpose: To determine the cause-specific mortality relative to that expected in a population-based incidence cohort of people with unprovoked seizures. Methods: The cohort comprises 224 inhabitants of Iceland first diagnosed as suffering from unprovoked seizures during a 5-year period from 1960 to 1964. The expected number of deaths was calculated by multiplying person-years of observation within 5-year age categories for each year from diagnosis through 1995 by cause-specific and sex-specific national death rates for those aged 20 years and above. The standardized mortality ratio (SMR) and 95% confidence intervals (95% CI) were calculated. Results: All-cause mortality was increased among men (SMR 2.25, 95% CI 1.56–3.14) but not women (SMR 0.79, 95% CI 0.38–1.46). Among men, there were 8 deaths from accidents, poisoning and violence observed versus 2.82 expected (SMR 2.84, 95% CI 1.22–5.59) and 4 deaths from suicide versus 0.69 expected (SMR 5.80, 95% CI 1.56–14.84). All-cause mortality for men was still elevated after restriction of analysis to those with seizures of unknown etiology (SMR 1.73, 95% CI 1.05–2.67) with the excess deaths attributable to suicide (SMR 5.26, 95% CI 1.06–15.38). Both males and females with remote symptomatic unprovoked seizures had an increase in all-cause mortality due to excess mortality from all cancers, cerebrovascular disease and accidents. Conclusion: When compared with the age-, time-period- and gender-specific mortality in the general population, there is excess mortality in men but not women. The increased mortality for men is partly attributable to excess mortality from accidents and suicides.

Autism Spectrum Disorders in Children with Seizures in the First Year of Life—A Population-based Study

Summary:  Purpose: To describe autistic spectrum disorders (ASDs) in a cohort of children with history of unprovoked seizures other than infantile spasms in the first year of life.

Mortality from cancer and other causes among male airline cockpit crew in Europe

Airline pilots and flight engineers are exposed to ionizing radiation of cosmic origin and other occupational and life‐style factors that may influence their health status and mortality. In a cohort study in 9 European countries we studied the mortality of this occupational group. Cockpit crew cohorts were identified and followed‐up in Denmark, Finland, Germany, Great Britain, Greece, Iceland, Italy, Norway and Sweden, including a total of 28,000 persons. Observed and expected deaths for the period 1960–97 were compared based on national mortality rates. The influence of period and duration of employment was analyzed in stratified and Poisson regression analyses. The study comprised 547,564 person‐years at risk, and 2,244 deaths were recorded in male cockpit crew (standardized mortality ratio [SMR] = 0.64, 95% confidence interval [CI] = 0.61–0.67). Overall cancer mortality was decreased (SMR = 0.68; 95% CI = 0.63–0.74). We found an increased mortality from malignant melanoma (SMR = 1.78, 95% CI = 1.15–2.67) and a reduced mortality from lung cancer (SMR = 0.53, 95% CI = 0.44–0.62). No consistent association between employment period or duration and cancer mortality was observed. A low cardiovascular mortality and an increased mortality caused by aviation accidents were noted. Our study shows that cockpit crew have a low overall mortality. The results are consistent with previous reports of an increased risk of malignant melanoma in airline pilots. Occupational risk factors apart from aircraft accidents seem to be of limited influence with regard to the mortality of cockpit crew in Europe.

Risk of autism spectrum disorders after infantile spasms: A population‐based study nested in a cohort with seizures in the first year of life

Purpose:  No population‐based study has investigated the risk of autism spectrum disorders (ASDs) in children after unprovoked seizures with onset in the first year of life. Our objective was to determine whether infantile spasms were related to risk of ASD as compared to unprovoked seizures with onset in the first year of life after adjusting for symptomatic origin of seizures.

Pelvic Endometriosis Diagnosed in an Entire Nation Over 20 Years

The annual incidence of pelvic endometriosis among women aged 15-49 years and up to age 69 years was ascertained for the Icelandic population between 1981 and 2000 by using Icelands extensive record linkage systems. Comprehensive, state-financed health care and unique personal identification numbers enabled care to be tracked from first diagnosis. To identify cases, a centralized discharge-code registry was searched, as well as all hospital databases and, for individual patients, all hospital records. Each case of visually diagnosed and histologically verified endometriosis was cross-checked against the nationwide pathology registry. The revised American Society for Reproductive Medicine classification system was used for staging. Recorded was type of operation at diagnosis and presence of disease at 5 sites: deep pelvis, appendages, central pelvis, vesicouterine pouch, and ovaries. A total of 1,383 women were diagnosed surgically, with histologic verification of 811 (58.6%). All but 6 cases could be staged; 297 (36.9%) had minimal/mild and 508 (63.1%) had moderate/severe disease. The estimates of crude annual incidence were 0.1% for visually confirmed and 0.06% for histologically verified endometriosis, and respective age-standardized annual incidence was 0.1% and 0.05% for women aged 15-49 years. The most common site was the ovary, followed by deep pelvis, central pelvis, appendages, and vesicouterine pouch.

Autism Spectrum Disorders in Children With a History of Infantile Spasms: A Population-Based Study

The objective of this article is to describe autistic spectrum disorders in children diagnosed with infantile spasms in the first year of life. The source of data was the records of all 3 pediatric departments in Iceland. Twenty children born between 1981 and 1998 who had infantile spasms were invited to participate. When appropriate, the parents of these children were asked to complete the Social Communication Questionnaire. Children scoring 10 points or higher on the questionnaire were selected for further examination using the Autism Diagnostic Interview− Revised and either the Autism Diagnostic Observation Schedule or the Childhood Autism Rating Scale. All participants were given appropriate cognitive tests or measures of adaptive behavior. The parents of 17 children (10 boys, 7 girls) agreed to participate in the study. Age at assessment ranged from 5 to 19 years with a mean age of 11 years and 6 months. Fourteen children had at least one neurodevelopmental disorder. Six (6/17), or 35.3%, were diagnosed with autism spectrum disorder (3 boys, 3 girls), five of these had a history of symptomatic infantile spasms, and four were profoundly mentally retarded (IQ/DQ<20). If the diagnosis of autism spectrum disorder was restricted to children with a developmental age of 24 months or more (3 cases), the prevalence was 17.6%. The estimates found in this study exceed the estimated prevalence of autism spectrum disorder in the general population.

Association between exposure to crystalline silica and risk of sarcoidosis

OBJECTIVES: The possibility of an association between exposure to silica and autoimmune diseases has recently come under discussion. In the following case-referent study, a cohort exposed to diatomaceous earth and cristobalite provided an opportunity to evaluate such an exposure with reference to sarcoidosis. METHODS: The inhabitants of a district served by a single healthcare centre and a hospital formed the study base. A diatomaceous earth plant is located in this community and the medical institutions are responsible for primary and secondary health care of the population. Cases of sarcoidosis were identified from the hospital records according to certain clinical, radiological, and histological criteria. Referents were selected randomly from the population of the district. Information on exposure to crystalline silica, cristobalite, was obtained by record linkage of the cases and referents with a file which included all present and past workers at the diatomaceous earth plant and those who had worked at loading vessels with the product from the plant. RESULTS: Eight cases of sarcoidosis were found, six of which were in the exposed group. Of the 70 referents, 13 were exposed. The odds ratio (95% confidence interval) was 13.2 (2.0 to 140.9). CONCLUSION: The odds ratios were high and there were some indications of a dose-response relation which will hopefully encourage further studies. To our knowledge this is the first study to indicate a relation between sarcoidosis and exposure to the crystalline silica, cristobalite.

Breast cancer risk in airline cabin attendants: a nested case-control study in Iceland

Aims: To investigate whether length of employment as a cabin attendant was related to breast cancer risk, when adjusted for reproductive factors. Methods: Age matched case-control study nested in a cohort of cabin attendants. The cases were found from a nationwide cancer registry (followed up to end of year 2000) and the reproductive factors (age at first childbirth and number of children) from a registry of childbirth, in both instances by record linkage with the cabin attendants’ identification numbers. The employment time of the cabin attendants at the airline companies and the reproductive factors had been systematically recorded prior to the diagnosis of breast cancer in the cohort. A total of 35 breast cancer cases and 140 age matched controls selected from a cohort of 1532 female cabin attendants were included in the study. Results: The matched odds ratio from conditional logistic regression of breast cancer risk among cases and controls of cabin attendants was 5.24 (95% CI 1.58 to 17.38) for those who had five or more years of employment before 1971 compared with those with less than five years of employment before 1971, adjusted for age at first childbirth and length of employment from 1971 or later. Conclusions: The association between length of employment and risk of breast cancer, adjusted for reproductive factors, indicates that occupational factors may be an important cause of breast cancer among cabin attendants; the association is compatible with a long induction period.