1. Leukemia following occupational exposure to 60-Hz electric and magnetic fields among Ontario electric utility workers

Anthony B Miller, Teresa To, David A Agnew, Claus Wall, Lois M Green
Am J Epidemiol 1996;144(2):150-60

In a nested case-control study of 1,484 cancer cases and 2,179 matched controls from a cohort of 31,543 Ontario Hydro male employees, the authors evaluated associations of cancer risk with electric field exposure and reevaluated the previously reported findings for magnetic fields. Pensioners were followed from January 1, 1970, and active workers (including those who left the corporation) from January 1, 1973, with both groups followed through December 31, 1988. Exposures to electric and magnetic fields and to potential occupational confounders were estimated through job exposure matrices. Odds ratios were elevated for hematopoietic malignancies with cumulative electric field exposure. After adjustment, the odds ratio for leukemia in the upper tertile was 4.45 (95% confidence interval (CI) 1.01-19.7). Odds ratios were also elevated for acute nonlymphoid leukemia, acute myeloid leukemia, and chronic lymphoid leukemia. For cumulative magnetic field exposure, there were similar elevations that fell with adjustment. Evaluation of the combined effect of electric and magnetic fields for leukemia showed significant elevations of risk for high exposure to both, with a dose-response relation for increasing exposure to electric fields and an inconsistent effect for magnetic fields. There was some evidence of a nonsignificant association for brain cancer and benign brain tumors with magnetic fields. For lung cancer, the odds ratio for high exposure to electric and magnetic fields was 1.84 (95% CI 0.69-4.94).

Michel Vézina, Suzanne Gingras
Can J Public Health 1996;87(2):135-40

Analysis of the Quebec Health Survey identified those Quebec industrial sectors and professions in which workers are at risk of higher psychological distress and lower psychological well-being. Risk levels were measured by odds ratio, controlling for: health status, sex, social support and stressful life events. Results show that those at risk are blue collar workers and less qualified workers of traditional sectors. Lower job latitude could explain those results. Results show that risk of mental health problems is significantly higher in the following industrial sectors: leather, chemicals, paint and varnish industries; urban bus transport and taxi; shoe, clothing and textile retail stores; department stores; restaurant services; insurance and public administration (excluding defence). Risk of mental health problems is higher in the following professions: road transport (excluding truck drivers); textile, leather, fur manufacturing and repairing; housekeeping and maintenance; painters, tapestry-workers, insulation and waterproofing; food and beverages sector; data processors; editors and university professors.

John Cairney, Robert Arnold
Can J Public Health 1996;87(3):199-203

Despite the vast amount of literature on the relationship between social class and health, little work has been done on post-retirement populations. Using the 1991 General Social Survey, a sample of respondents (N = 1,943) aged 65 to 99 were selected for analysis. Three social class variables, income adequacy, education and occupation, were used along with several lifestyle variables and demographic controls to predict six different measures of health status. The findings supported a "condition-specific" approach to the study of class differences in morbidity. Income adequacy was the most consistent class predictor of these health measures in this sample. As well, 'risky' lifestyle variables were used to test the hypothesis that such factors may mediate the relationship between class and health. This hypothesis was not well supported in these data.

MaryFran Sowers, Marc Hochberg, Jeffrey P Crabbe, Anthony Muhich, Mary Crutchfield, Sharon Updike
Am J Epidemiol 1996;143(1):38-47

Mechanical stress on the cartilage and metabolic and/or hormonal influences have been suggested as possible etiologic factors for osteoarthritis. This paper reports findings from data collected in 1992 that were used to examine associations between osteoarthritis and risk factors in 573 Caucasian women aged 24-45 years from the Michigan Bone Health Study. Radiographs of the dominant hand and both knees were evaluated using the Kellgren and Lawrence grading scale. The prevalence of osteoarthritis (grade 2 or higher) in this population was 2.8% for hands and 3.6% for knees. Using polytomous multiple logistic regression, the authors found older age, increasing bone mineral density, and decreasing testosterone levels to be significantly associated with increasing hand scores. Older age and hand injury were significantly associated with grades of 2 or higher. Increasing osteoarthritis knee scores were associated with older age, increasing bone density, increasing body mass index, and current use of hormone replacement therapy. A knee grade of 2 or higher was associated with increasing estradiol levels, knee injury, and higher blood pressure. This study indicates that age, bone density, and injury are risk factors common to the development of hand and knee osteoarthritis in this non-elderly female population.

Marcia M Johnson, T Gregory Hislop, Lisa Kan, Andrew J Coldman, Alec Lai
Can J Public Health 1996;87(3):176-80

Objective: To identify factors associated with compliance in the Screening Mammography Program of British Columbia (SMPBC).

Method: Factors associated with rescreening within 18 months (annual compliers) and between 18 to 36 months later (late compliers) were identified in a cohort of SMPBC screenees using a self-administered questionnaire.

Results: Fewer than half of women initially screened within the SMPBC were annual compliers, nearly 40% not returning by 3 years. In women age 50+ years, annual compliers tended to have no prior mammography, no prior breast pain, a physician referral to SMPBC, and a normal initial SMPBC mammogram. Late compliers also tended to have no prior mammography, a physician referral, and a normal initial SMPBC mammogram.

Conclusions: Several modifiable factors associated with compliance were identified: a physician referral to the program and possibly subsequent referral back to the program after workup for an abnormal mammogram.

Thomas Gregory Hislop, Heather Frances Clarke, Michèle Deschamps, Rhea Joseph, Pierre Robert Band, John Smith, Nhu Le, Richard Atleo
Can Fam Physician 1996;42:1701-8

Objective: To determine Pap smear screening rates among urban First Nations women in British Columbia; to identify facilitators and barriers; and to develop, implement, and evaluate specific interventions to improve Pap smear screening in Vancouver.

Design: Computer records of band membership lists and the Cervical Cytology Screening Program registry were compared to determine screening rates; personal interviews and community meetings identified facilitators and barriers to urban screening programs. A community advisory committee and the project team collaborated on developing specific interventions.

Setting and Participants: Purposive sample of British Columbia First Nations women, focusing on women living in Vancouver. Interventions: Poster, art card, and follow-up pamphlet campaign; articles in First Nations community papers; community meetings; and Pap smear screening clinics for First Nations women.

Main Outcome Measures: Pap smear screening rates among BC First Nations women according to residence and reasons for not receiving Pap smears.

Results: Pap smear screening rates were substantially lower among First Nations women than among other British Columbia women; older women had even lower rates. No clear differences were found among First Nations women residing on reserves, residing in Vancouver, or residing off reserves elsewhere in British Columbia. Facilitators and barriers to screening were similar among women residing on reserves and in Vancouver. Many First Nations women are greatly affected by health care providers' attitudes, abilities to provide clear information, and abilities to establish trusting relationships.

Conclusions: Family physicians are an important source of information and motivation for Pap smear screening among First Nations women.

Catherine E De Grasse, Annette M O'Connor, Daniele J Perrault, Susan E Aitken, Suzie Joanisse
Can J Public Health 1996;87(5):333-8

Although Canadian Breast Screening Guidelines have been in place since 1988, participation rates have been suboptimal. The study objective was to describe changes in breast screening knowledge, attitudes, and practices among women aged 50 to 69 years since initiation of a regional mass screening program in Ottawa-Carleton in 1991.

A random-digit-dialling telephone survey was conducted with 384 women aged 50 to 69 years residing in Ottawa-Carleton and compared to a 1991 survey.

Between 1991 and 1994 there were significant increases in the percentage ever having had a mammogram (from 60% to 83%) and monthly breast self-examination (from 46% to 54%). Professional breast examination rates were unchanged as were overall attitudes and concerns about screening. There were significant improvements in knowledge and encouragement to have a mammogram.

As the focus on primary health care within our health care system grows, and as service delivery changes, we must continue to search for, and continually evaluate, innovative strategies to align practices with Canadian breast screening recommendations.

Robert A Spasoff, Carol J Strike, Rama C Nair, Geoffrey C Dunkley, Jack R Boulet
Can J Public Health 1996;87(2):130-4

We used synthetic estimation and linear regression to estimate the prevalence of selected risk factors and health status indicators in small populations. The derivation was based on the sociodemographic characteristics of the populations and the relationships between these variables and the health variables, as measured by the Ontario Health Survey (OHS). The estimates were validated by a comparison with the direct results of the OHS (gold standards).

Synthetic estimates were much less dispersed than the regression estimates or the direct OHS estimates. Regression estimates performed better than synthetic estimates on most validation indicators, and combined approaches performed marginally better yet, although there were few clear patterns. Although correlation coefficients with gold standards in excess of 0.8 were obtained for some variables, the estimates rarely met predetermined criteria for accuracy. At present these techniques have limited value for public health workers, but further work is justified, especially on approaches combining synthetic and regression estimation.

Kenneth R Allison
Can J Public Health 1996;87(5):354-8

This paper develops a profile of the inactive population in Ontario. The findings were based on an analysis of data from the 1990 Ontario Health Survey. A Physical Activity Index, including frequency, duration, and an estimate of intensity, was used to classify individuals on the basis of their leisure time physical activity levels. Inactives comprised the group estimated to average less than 1.5 kcals/kg/day of energy expenditure. Multiple logistic regression was used to estimate the odds of inactivity for a number of predictor variables. Age, gender, friends' participation, perceived health status, and perceived future health problems were the strongest predictors of physical inactivity. The findings contribute to a further understanding of the factors influencing physical activity participation and promotion.

Edward M Adlaf, Frank J Ivis, Reginald G Smart, Gordon W Walsh
Can J Public Health 1996;87(3):189-92

This paper describes trends in alcohol and other drug use among Ontario students between 1977 and 1995, especially those occurring between 1993 and 1995. Data are based on the Ontario Student Drug Use Survey, which to date represents 10 cross-sectional surveys conducted every two years since 1977. In each survey, approximately 4,000 students in grades 7, 9, 11 and 13 are interviewed in their classrooms. The findings show that after a decade of declining drug use, rates of use increased between 1993 and 1995. Of the 20 drugs surveyed in 1995, the use of 8 increased significantly from 1993. Increases in drug use were more common among 9th- and 11th-graders.

Brian F Habbick, Josephine L Nanson, Richard E Snyder, Robin E Casey, Ann L Schulman
Can J Public Health 1996;87(3):204-7

Despite major initiatives in public and professional education about foetal alcohol syndrome (FAS) in Saskatchewan in the last 20 years, its incidence rate has not fallen. The rate was 0.515 per 1,000 live births in 1973-1977 and 0.589 in 1988-1992.

Two hundred and seven (207) cases were ascertained, the majority being patients of the Alvin Buckwold Child Development Program in Saskatoon. These individuals were severely handicapped: 72% had at least one malformation, the mean intelligence quotient was 67.8 (range 35-106) and 45.9% had a behaviour problem. Only 25.6% still lived with their biological parents when last seen, and only 27 of 108 cases were in a regular class at school without additional support being necessary.

New approaches are needed to reduce the incidence of FAS. Emphasis should be placed on individual case-finding, counselling for high-risk women, and community development programs. We are currently attempting this through a provincial coordinating committee.

Susan A Oliveria, David T Felson, Raymond A Klein, John I Reed, Alexander M Walker
Epidemiology 1996;7:415-9

Recent studies have indicated that estrogen users have a lower than expected rate of concurrent osteoarthritis. We assessed the association between estrogen replacement therapy and incident symptomatic osteoarthritis, using a nested case-control design. We identified all incident cases of hand, hip, and knee osteoarthritis in women members of the Fallon Community Health Plan, age 20-89 years, from January 1, 1990, to December 31, 1993. For each case, we selected a control woman matched by closest date of birth. We used pharmacy records to classify women as new users, past users, ongoing users (past and new users), and never-users of estrogen replacement therapy. There were 60 informative case-control pairs. After controlling for obesity and health care utilization, we found that new use of estrogen replacement therapy was a predictor of new osteoarthritis diagnosis. Past use was inversely associated with risk of osteoarthritis [adjusted odds ratio = 0.7; 95% confidence interval (CI) = 0.3-1.9]. For ongoing use of estrogen replacement therapy and osteoarthritis, the adjusted odds ratio was 1.4 (95% CI = 0.6-3.3). The associations between osteoarthritis and both new use of estrogen replacement therapy and utilization of services suggest that frequent medical care increases the likelihood of diagnosis of osteoarthritis.

Bruce P Lanphear, Michael Weitzman, Nancy L Winter, Shirley Eberly, Benjamin Yakir, Martin Tanner, Mary Emond, Thomas D Matte
Am J Public Health 1996;86(10):1416-21

Objectives. This study assessed the relationship between lead-contaminated house dust and urban children's blood lead levels.

Methods. A random-sample survey was used to identify and enroll 205 children, 12 to 31 months of age, who had resided in the same house since at least 6 months of age. Children's blood and household dust, water, soil and paint were analyzed for lead, and interviews were conducted to ascertain risk factors for elevated blood lead (³10ug/dL).

Results. Children's mean blood lead level was 7.7 mg/dL. In addition to dust lead loading (micrograms of lead per square foot), independent predictors of children's blood lead were Black race, soil lead levels, ingestion of soil or dirt, lead content and condition of painted surfaces, and water lead levels. For dust lead standards of 5 mg/sq ft, 20 mg/sq ft, and 40 mg/sq ft on noncarpeted floors, the estimated percentages of children having blood lead levels at or above 10 mg/dL were 4%, 15%, and 20%, respectively, after adjusting for other significant covariates.

Conclusions. Lead-contaminated house dust is a significant contributor to lead intake among urban children who have low-level elevations in blood lead. A substantial proportion of children may have blood lead levels of at least 10 mg/dL at dust lead levels considerably lower than current standards.

Juha P Liira, Harry S Shannon, Larry W Chambers, Theodore A Haines
Am J Public Health 1996;86(3):382-7

Objectives. This study sought to provide data on the relationship of work exposures to long-term back problems in a population survey.

Methods. The Ontario Health Survey in 1990 used a representative population sample of the province. It included data on long-term back problems, occupational activity, and physical work exposures. The current study examined relationships between these variables.

Results. The prevalence of long-term back problems was 7.8% in working-age adults. It generally increased with age. Long-term back problems were more prevalent in blue-collar occupations and among those not working, as well as among people with less formal education, smokers, and those overweight. Physical work exposures-awkward working position, working with vibrating vehicles or equipment, and bending and lifting-were all associated with a greater risk of back problems. The number of simultaneous physical exposures was monotonically related to increased risk.

Conclusions. Within the limitations of the data and assuming the relationship to be causal, about one quarter of the excess back pain morbidity in the working population could be explained by physical work exposures.

Cande V Ananth, David A Savitz, Edwin R Luther
Am J Epidemiol 1996;144(9):881-9

The authors carried out an epidemiologic study to evaluate the role of maternal cigarette smoking as a potential risk factor for placenta abruption, placenta previa, and uterine bleeding of unknown etiology in pregnancy. Data for this prospective cohort study were obtained from women seeking prenatal care at any of the two tertiary, seven regional, or 17 community hospitals in the province of Nova Scotia, Canada, between January 1, 1986 and December 31, 1993. A total of 87,184 pregnancies (among 61,667 women) were registered in the database. Women who smoked during pregnancy (33%) were compared with nonsmokers, and all women were followed until the termination of pregnancy. Placenta abruption was indicated in 9.9 per 1,000 pregnancies, while placenta previa and uterine bleeding of unknown etiology were indicated in 3.6 and 58.9 per 1,000 pregnancies, respectively. Women who smoked had a twofold increase in the risk of abruption (relative risk = 2.05, 95% confidence interval (CI) 1.75-2.40) in comparison with nonsmokers, while the relative risk for placenta previa was 1.36 (95% CI 1.04-1.79). However, cigarette smoking was not found to be associated with uterine bleeding of unknown etiology (relative risk = 1.01, 95% CI 0.94-1.08). There was no evidence for an increased risk of uteroplacental bleeding disorders with increasing numbers of cigarettes smoked. All analyses were adjusted for potentially confounding factors through logistic regression models based on the method of generalized estimating equations. The study confirms a positive association between cigarette smoking and placenta abruption and a weak association with placenta previa but not with other uterine bleeding. The distinct pattern of results for placental abruption, placenta previa, and uterine bleeding of unknown origin suggests that these three uteroplacental bleeding disorders do not have a common etiology in relation to cigarette smoking.

Anne-Marie Landtblom, Ulf Flodin, Birgitta Söderfeldt, Christina Wolfson, Olav Axelson
Epidemiology 1996;7:429-33

To evaluate the possible relation between exposure to organic solvents and the development of multiple sclerosis, we carried out a best-evidence synthesis of the available information. We found 13 studies with varying methodology that included information on solvent exposure. In 10 of the studies, there were indications of an increased risk of multiple sclerosis in relation to solvent exposure. We made three selections of studies for both pooled analyses and meta-analyses. The relative risk point estimates that we obtained varied from 1.7 to 2.6. Our evaluation is consistent with the hypothesis that organic solvents may be a cause of multiple sclerosis.

Yue Chen, Donna C Rennie, James A Dosman
Epidemiology 1996;7:536-9

The relation between exposure to environmental tobacco smoke and childhood asthma is not clear. A 1993 study of 892 subjects age 6-17 years (87.5% of 1,019 eligible subjects) living in Humboldt, Saskatchewan, showed that a lifetime history of asthma and asthma attack during the past 12 months were more common among allergic children than among non-allergic children. The number of household smokers and total daily cigarette consumption by household members were linearly related to both lifetime history of asthma and recent asthma in nonallergic children, but not in allergic children. Our study indicates that allergic status does alter the relation between exposure to environmental tobacco smoke and childhood asthma.

Antoine Chapdelaine, Pierre Maurice
Can Med Assoc J 1996;155(9):1285-9

Firearms cause more than three deaths daily in Canada. The rate of mortality from gunshot wounds varies among provinces and territories, ranging from 5.7 to 21.2 per 100, 000 people. Most deaths from gunshot wounds occur in the home, with more occurring in rural areas than in cities, and are inflicted with legally acquired hunting guns. The cost of the consequences of the improper use of firearms in Canada has been estimated at $6.6 billion per year. There is a correlation between access to guns and risk of death. The mere presence of a firearm in a home increases the risk of suicide, homicide and "accidental" death. It is estimated that, in one third of all households in Quebec that have a firearm, it is not safely, or even legally, stored. To prevent deaths and injuries from firearms, education is not enough. Environmental, technological and legislative measures are also needed. In this spirit, the Quebec Public Health Network has taken a position supporting better controls on access to firearms, including the licensing and registration of all firearms and their ownership, to prevent deaths and injuries. The network believes that licensing and registration will reduce the problems related to firearms by making owners accountable for the use of their firearms, improving public safety, helping to control the import and circulation of firearms, reinforcing research and education, and reducing access to firearms in homes. Licensing and registration do not interfere with legitimate firearm use, their cost is acceptable in light of the advantages they provide, and they are desired by most Canadians.

KS Joseph, Michael S Kramer
Can Med Assoc J 1996;155(8):1047-52

Objective: To ascertain whether the increase in the crude infant mortality rate in Canada in 1993 was due to a recent increase in the registration of newborns weighing less than 500 g as live births.

Design: Ecological study, with Poisson regression analysis.

Setting: Canada.

Subjects: All live births and infant deaths in Canada between 1981 and 1993, as reported by Statistics Canada. Data from Newfoundland were excluded because they were incomplete for 4 years.Outcome measures: Proportion of live births by low-birth-weight category; and annual crude and adjusted infant mortality rates.

Results: Over the study period the proportion of newborns weighing less than 500 g registered as live births increased significantly (c 2 for trend = 71.26, p < 0.01). This trend was an isolated phenomenon rather than a general increase in all low-birth-weight categories (c 2 for trend in the proportion of newborns weighing 500 to 2 400 g registered as live births = 1.14, p = 0.28). The crude infant mortality rate per 1 000 live births decreased from 6.4 in 1991 to 6.1 in 1992 and then increased to 6.3 in 1993. Poisson regression analysis revealed that the apparent increase in the infant mortality rate was caused by the increased registration of infants weighing less than 500 g as live births. The adjusted infant mortality estimate for 1993 was lower than that for 1992.

Conclusions: The increased infant mortality rate in Canada in 1993 appears to be due to increased registration of infants weighing less than 500 g as live births. Comparisons of infant mortality rates by place and time should be adjusted for the proportion of such live births, especially if the comparisons involve recent years.