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The following supplemental information accompanies a News article by Volkers, J Natl Cancer Inst 2002;94:1826–7:
Selected Studies in Cancer Epidemiology
Cancer Risk Among Butchers:
- Boffetta P, Gridley G, Gustavsson P, Brennan P, Blair A, Ekstrom AM, Fraumeni JF Jr. Employment as butcher and cancer risk in a record-linkage study from Sweden. Cancer Causes Control 2000 11:627-633. [Medline]
Butchers/meat workers had a slightly increased risk of cancer (RR 1.1; CI 1.0-1.3) due to incerases in the risk of oral and pharyngeal cancer (RR 1.6; CI 1.0-2.7), stomach cancer (1.6; 1.1-2.7), and lung cancer (1.4; 1.1-1.9). Risk of stomach cancer was the highest during the first 5 years of the study and highest among urban butchers. The authors conclude that these risks could be due to lifestyle factors (drinking, smoking, etc) or due to industry-specific exposures, such as viruses, nitrosamines, or polycyclic aromatic hydrocarbons.
- Bethwaite P, McLean D, Kennedy J, Pearce N. Adult-onset acute leukemia and employment in the meat industry: a New Zealand case-control study. Cancer Causes Control 2001 Sep;12(7):635-43. [Medline]
This study found a fivefold increased risk of adult acute leukemia among adults who had worked in an abattoir and had direct contact with animals for more than 2 years. Ever having worked as a butcher in an abattoir (OR 4.8) or butchering livestock on farms (OR 8.2) also was associated with increased risk. No increased risks were found for work as a retail/wholesale butcher or meatpacker.
- Metayer C, Johnson ES, Rice JC. Nested case-control study of tumors of the hemopoietic and lymphatic systems among workers in the meat industry. Am J Epidemiol 1998 Apr 15;147(8):727-38. [Medline]
A case–control study nested in a cohort of members of a meatcutter's union found excess risks of hemopoietic and lymphatic tumors of the hemopoietic and lymphatic systems throughout the meat industry, except in meatpacking plants. Butchers who killed animals had an elevated risk (OR = 5.3, 95% confidence interval (CI) 1.0-27.0); as did workers in chicken-slaughtering plants (OR = 3.3, 95% CI 0.8-13.1); and workers in cattle/sheep/pig abattoirs (OR = 2.8, 95% CI 0.8-9.5). Among supermarket workers, wrapping meat was associated with increased risk of tumors of the hemopoietic and lymphatic systems (OR = 3.8, 95% CI 1.0-14.3). On the other hand, meatcutting in supermarkets was associated with multiple myeloma (OR = 18.0, 95% CI 1.6-207.5), with no myeloma cases being recorded in women. These associations persisted after limited control for exposures such as exposure to pesticides, working/living on pig farms, and exposure to X-rays.
Cancer risk among flight attendants:
- Reynolds P, Cone J, Layefsky M, Goldberg DE, Hurley S. Cancer incidence in California flight attendants (United States). Cancer Causes Control 2002 May;13(4):317-24. [Medline]
This study looked at cancer incidence among members of the Association of Flight Attendants (AFA) residing in California. Compared with the general population, female breast cancer incidence was more than 30% higher than expected, and malignant melanoma incidence was roughly twice that expected. Both of these are cancers that are associated with higher socioeconomic status and have been suggestively associated with various sources of radiation.
- Rafnsson V, Tulinius H, Jonasson JG, Hrefnkelsson J. Risk of breast cancer in female flight attendants: a population-based study (Iceland). Cancer Causes Control 2001;12(2):95-101. [Medline]
The authors found increased risk of all cancers (1.3; 1.0-1.8) as well as breast cancer (1.6; 1.0-2.4) in female flight attendants, using a 15-year lag time. Attendants hired in 1971 or later had the heaviest exposures to cosmic radiation and also had higher overall risks of any cancer (2.8) and breast cancer (4.1). Reproductive factors (children vs no children and number of children) did not show risk increases.
- Ballard T, Lagorio S, De Angelis G, Verdecchia A. Cancer incidence and mortality among flight personnel: a meta-analysis. Aviat Space Environ Med 2000 Mar;71(3):216-24. [Medline]
This Italian study looked at all published and unpublished cohort studies of flight personnel from 1986 to 1998. The authors used 6 studies, 4 of pilots and 2 of flight attendants. Risks were elevated among male pilots for mortality from melanoma (RR = 11.97, 95% CI: 1.02-3.82) and for risk of cancer of the prostate (RR = 1.65, CI: 1.19-2.29). Among female flight attendants, increases were seen for breast cancer (RR = 1.35, CI: 1.00-1.83).
- Pukkala E, Auvinen A, Wahlberg G. Incidence of cancer among Finnish airline cabin attendants, 1967-92. BMJ 1995 Sep 9;311(7006):649-52. [Medline]
The authors studied 1577 female and 187 male cabin attendants who had worked for Finnish airlines. They found significant excesses of breast cancer (SIR = 1.87, 95% CI: 1.15 to 2.23) and bone cancer (SIR = 15.10, 95% CI: 1.82 to 54.40) among female workers. The risk of breast cancer was most prominent 15 years after recruitment. There were no elevated risks among the men. The authors conclude that the concentration of the excess risks to primary sites sensitive to radiation suggests that ionizing radiation during flights may add to the cancer risk of all flight personnel. Otherwise, the lifestyle of cabin attendants did not seem to affect their risks of cancer, and estimates of the effect of reproductive risk factors only partly explained the increased risk of breast cancer.
- Ballard TJ, Lagorio S, De Santis M, De Angelis G, Santaquilani M, Caldora M, Verdecchia A. A retrospective cohort mortality study of Italian commercial airline cockpit crew and cabin attendants, 1965-96. Int J Occup Environ Health 2002 Apr-Jun;8(2):87-96 [Medline]
The authors conducted a retrospective cohort mortality study of Italian commercial flight personnel for the period 1965-1996. The cohort was composed of 3,022 male cockpit crew members and 3,418 male and 3,428 female cabin attendants. In all categories, there were fewer deaths from all cancers than expected (SMRs of 0.58 for male cockpit crew, 0.67 for male cabin attendants, and 0.90 for female cabin attendants). Among male flight personnel, the SMR for leukemia was somewhat elevated (SMR 1.73; 95% CI: 0.75-3.41) based on eight deaths, with a positive trend by length of employment (p = 0.046). Additionally, an excess of death by suicide was seen among female cabin attendants (SMR 3.38; 95% CI: 1.24-7.35).
Orthopedic prostheses and cancer risk:
- Coleman MP. Cancer risk from orthopedic prostheses. Ann Clin Lab Sci 1996;26(2):139-146. [Medline]
Prolonged contact of metals with body fluids will corrode the metals. Three cohort studies of people with hip prostheses have been done; collectively, they examined cancer risk in nearly 41,000 people for a mean of 8.5 years after hip replacement. Overall, the relative risk of cancer was slightly increased (1.02; 1.00-1.05). there were significant decreased risks of breast and colorectal cancers seen in two of the studies, but combined results do not show these decreases. Cancer risk in the first 10 years after hip replacement was not different than expected, but 10 or more years after replacement, the risk was 1.08 (1.00-1.13) in 1,005 people.
- Signorello LB, Ye W, Fryzek JP, Lipworth L, Fraumeni JF Jr, Blot WJ, McLaughlin JK, Nyren O. Nationwide study of cancer risk among hip replacement patients in Sweden. J Natl Cancer Inst 2001 Sep 19;93(18):1405-10. [Medline]
The authors examined cancer incidence among 116,727 patients who underwent hip replacement surgery from 1965 through 1994. Relative to the general population, the cohort had no overall cancer excess (SIR = 1.01; 95% confidence interval [CI] = 0.99 to 1.03). However, they observed elevated SIRs for prostate cancer (SIR = 1.16; 95% CI = 1.11 to 1.22) and melanoma (SIR = 1.15; 95% CI = 1.01 to 1.30) and a reduction in stomach cancer risk (SIR = 0.83; 95% CI = 0.75 to 0.92). Long-term follow-up (> or = 15 years) revealed an excess of multiple myeloma (SIR = 1.86; 95% CI = 1.01 to 3.11). There was no material increase in risk for bone or connective tissue cancer for either men or women in any follow-up period.
- Paavolainen P, Pukkala E, Pulkkinen P, Visuri T.Cancer incidence in Finnish hip replacement patients from 1980 to 1995: a nationwide cohort study involving 31,651 patients. J Arthroplasty 1999 Apr;14(3):272-80. [Medline]
There were statistically significantly fewer cancers among hip replacement patients (standardized incidence ratio [SIR], 0.90; 95% confidence interval [CI], 0.87-0.93). SIRs for cancers of the lung (0.69) and stomach (0.77) were significantly below unity. There was no significantly increased risk at any site. The authors conclude that hip replacement seems to play no major role in cancer causation.
Marital Status and Cancer Risk:
- Kvikstad A, Vatten LJ. Cancer risk and prognosis in Norway: comparing women in their first marriage with women who have never been married. J Epidemiol Community Health 1996;50(1):51-55. [Medline]
Unmarried women had an overall increased cancer risk (OR = 1.13; 95% CI: 1.05-1.21) attributed to cancers of the uterus, ovary, brain, and hematologic malignancies. For cervical and thyroid cancer, unmarried women had lower risks than did married women. Unmarried women had an increased risk of dying from cancer (OR = 1.26; 95% CI: 1.15-1.39) after adjusting for age and stage at diagnosis. The authors note that, because most unmarried women did not have children, this could account for the increases in risks of ovarian and uterine cancers. Brain and hematologic cancer risks may have resulted from selection bias (disease among unmarried women may cause a large proportion to remain unmarried). They suggest that their study suppors the hypothesis that psychosocial factors play a role in the prognosis of cancer patients.
- Kvikstad A, Vatten LJ, Tretli S. Widowhood and divorce in relation to overall survival among middle-aged Norwegian women with cancer. Br J Cancer 1995 Jun;71(6):1343-7. [Medline]
The authors looked at all Norwegian women born between 1935 and 1954, and diagnosed with cancer between 1966 and 1990. In all, 14,231 cases were followed up a mean of 6 years. The risk of dying was nearly identical among widows and married women for all sites except colorectal cancer, for which widows had a twofold increased death rate. Divorced women had an overall increased hazard ratio of death from cancer of 1.17 (95% CI 1.07-1.27), which was confined to cancer of the breast, lung and cervix. With few clear exceptions, women with children had a better survival than nulliparous women (overall hazard ratio = 0.80, 95% CI 0.74-0.87).
- Kvikstad A, Vatten LJ, Tretli S, Kvinnsland S. Widowhood and divorce related to cancer risk in middle-aged women. A nested case-control study among Norwegian women born between 1935 and 1954. Int J Cancer 1994 Aug 15;58(4):512-6. [Medline]
The authors examined whether the risk of cancer among divorced or widowed Norwegian women born between 1935 and 1954 was any different from that of married women. For widowed women, there was no overall increased risk of cancer. For divorced women, a reduced risk was seen for cancers of a number of sites, including thyroid, endometrium, colorectum, and breast, as well as malignant melanoma and hematologic malignancies, with statistically significant estimates of relative risk ranging from 0.64 to 0.84. In contrast, divorced women had strongly elevated risks of lung and cervical cancer. Moreover, there was a gradual reduction in the relative risk of cancer at some sites with increasing age at divorce, and with duration of marriage prior to divorce.
- Kvikstad A, Vatten LJ, Tretli S, Kvinnsland S.Death of a husband or marital divorce related to risk of breast cancer in middle-aged women. A nested case-control study among Norwegian women born 1935-1954. Eur J Cancer 1994;30A(4):473-7. [Medline]
In a study that included 4491 incident breast cancer cases and 44,910 controls, matched on age, the risk of breast cancer among widowed women compared with married women was no higher. For divorced women the risk was significantly lower than that of married women (OR = 0.83; 95% CI: 0.75-0.92), after adjusting for age at first birth, parity and place of residence.
Night shift work and cancer risk:
- Schernhammer ES, Laden F, Speizer FE, Willett WC, Hunter DJ, Kawachi I, Colditz GA. Rotating night shifts and risk of breast cancer in women participating in the Nurses' Health Study. J Natl Cancer Inst 2001:93(20):1563-1568. [Medline]
The study summarizes 10 years of follow-up in 78,562 women in the NHS. (1988-1998) They found an increased risk of breast cancer in women who worked 30 or more years on the night shift: (RR = 1.36; 95% CI: 1.04-1.78) and nearly significant risks for those working 1-14 years on the night shift (RR = 1.08; 95% CI: 0.99-1.18) and those working 15-29 years (RR= 1.08; 95% CI: 0.90-1.3).
- Davis S, Mirick DK, Stevens RG. Night shift work, light at night, and risk of breast cancer. J Natl Cancer Inst 2001 Oct 17;93(20):1557-62. [Medline]
This study investigated whether exposure to light at night is associated with an increased risk of breast cancer in women. The authors studied 813 case patients with breast cancer and 793 control patients. The authors gathered information on sleep habits and bedroom lighting in the 10 years before diagnosis, as well as lifetime occupational history. Breast cancer risk was increased among subjects who frequently did not sleep during the period of the night when melatonin levels are typically at their highest (OR = 1.14 for each night per week; 95% CI = 1.01-1.28). Risk did not increase with interrupted sleep accompanied by turning on a light. There was an indication of increased risk among subjects with the brightest bedrooms. Graveyard shiftwork was associated with increased breast cancer risk (OR = 1.6; 95% CI = 1.0 to 2.5), with a trend of increased risk with increasing years and with more hours per week of graveyard shiftwork.
- Hansen J. Increased breast cancer risk among women who work predominantly at night. Epidemiology 2001 Jan;12(1):74-7. [Medline]
The authors investigated breast cancer risk among 30- to 54-year-old Danish women who worked predominantly at night. The odds ratio for breast cancer among women who worked at night at least half of a year was 1.5 (95% confidence interval, 1.2 to 1.7), and there was a tendency to increasing odds ratio by increasing duration of nighttime employment.
Pets and Cancer:
- Bertone ER, Snyder LA, Moore AS. Environmental tobacco smoke and risk of malignant lymphoma in pet cats. Am J Epidemiol 2002 Aug 1;156(3):268-73. [Medline]
The authors conducted a case-control study of 80 cats with malignant lymphoma and 114 controls with renal disease. Owners of all subjects were sent a questionnaire inquiring about the level of smoking in the household 2 years prior to diagnosis. After adjustment for age and other factors, the relative risk of malignant lymphoma for cats with any household ETS exposure was 2.4 (95 percent confidence interval: 1.2, 4.5). Risk increased with both duration and quantity of exposure, with evidence of a linear trend. Cats with 5 or more years of ETS exposure had a relative risk of 3.2 (95 percent confidence interval: 1.5, 6.9; p for trend = 0.003) compared with those in nonsmoking households.
- Reif JS, Dunn K, Ogilvie GK, Harris CK. Passive smoking and canine lung cancer risk. Am J Epidemiol 1992 Feb 1;135(3):234-9. [Medline]
A weak relation was found for exposure to a smoker in the home (odds ratio = 1.6, 95% confidence interval 0.7-3.7), after controlling for confounding in stratified analyses. Strong evidence for a further increase in risk associated with more than one smoker in the home was not found, nor was a significant trend observed for increasing number of packs of cigarettes smoked per day or an exposure index based on number of smokers in each household, packs smoked per day, and the proportion of time the dog spent within the home. However, skull shape appeared to exert effect modification; the risk was restricted to breeds with short and medium length noses (odds ratio = 2.4, 95% confidence interval 0.7-7.8).
- Swensen AR, Ross JA, Shu XO, Reaman GH, Steinbuch M, Robison LL.Pet ownership and childhood acute leukemia (USA and Canada). Cancer Causes Control 2001 May;12(4):301-3. [Medline]
The authors analyzed data from 2359 cases of acute leukemia from two large case–control studies. There was no association between pet ownership (either "any pet", dog, or cat) and childhood acute leukemia (OR(any pet:) = 1.01, 95% CI 0.89-1.2). Additionally, no relationship was found between exposure to an ill pet and childhood leukemia.
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