Saskatchewan Population Research Articles

Beyond the divides: Towards critical population health research

The term ‘population health’ has supplanted that of public health and health promotion in many Anglophone countries. The ideas underlying the term are not new and owe much to the legacies of nineteenth-century public health radicalism, Latin American social medicine and, more recently, social epidemiology. Its influential modeling by the Canadian Institute for Advanced Research in the early 1990s, however, was criticized for a lack of theory, reliance on large data sets, a simplistic modeling of the healthcare/economy relationship, little attention to the physical environment and an absence of human agency. While researchers working under the rubric of population health have addressed many of these early limitations, there has yet to be an articulation of what comprises a critical population health research practice. This article, based on the discussions and work of an interdisciplinary group of researchers in the Saskatchewan Population Health and Evaluation Research Unit (SPHERU) in Canada, argues that such a practice proceeds from a theoretical engagement (theories of knowledge, society and social change), community engagement (a politicization of research knowledge) and policy engagement (which must extend beyond the simplistic notions of ‘knowledge translation’ that now permeate the research communities). A critical population health research practice, it concludes, is a moral praxis built upon explicit social values and analyses.

The relationship between molecular and pathogenic variability in a Saskatchewan population of Mycosphaerella graminicola

Considerable molecular variability exists in Mycosphaerella graminicola, the cause of the important foliar disease septoria tritici blotch of wheat, but the relationship of this variability to pathogenic variability is unknown. This study examined this relationship to determine whether estimation of molecular variability has value for predicting the potential for pathogenic change in this pathogen. Ninety isolates of M. graminicola were collected using hierarchical sampling of leaves and lesions from 10 locations within a field, near Saskatoon, Saskatchewan, seeded to the hexaploid wheat cultivar ‘CDC Teal’. The pathogenicity of these isolates was evaluated on the susceptible cultivar ‘Conway’ by measuring incubation period, latent period, and disease severity. Significant differences were found among isolates for all components at the lesion sampling level but not at the leaf and location level. The percentage of polymorphic loci and gene diversity of the population was estimated using 15 RAPD primers. A high level of molecular variability existed within the population (H T = 0.179). Partitioning this variability showed that 64% of the variability was distributed within leaves, 22% among leaves, and only 14% among locations. A poor relationship between molecular and pathogenic variability was found, suggesting that DNA fingerprinting has little value for monitoring the development of new virulent genotypes of the pathogen.

Microsatellite markers provide evidence for sexual reproduction ofMycosphaerella graminicolain Saskatchewan

This study examined the genetic structure of a Saskatchewan population of Mycosphaerella graminicola, cause of the foliar disease Septoria tritici blotch of wheat. Such knowledge is valuable for understanding the evolutionary potential of this pathogen and for developing control strategies based on host resistance. Nine pairs of single-locus microsatellite primers were used to analyze the genomic DNA of 90 isolates of M. graminicola that were collected using a hierarchical sampling procedure from different locations, leaves, and lesions within a wheat field near Saskatoon. Allelic series at eight different loci were detected. The number of alleles per locus ranged from one to five with an average of three alleles per locus. Genetic diversity values ranged from 0.04 to 0.67. Partitioning the total genetic variability into within- and among-location components revealed that 88% of the genetic variability occurred within locations, i.e., within areas of 1 m(2), but relatively little variability occurred among locations. Low variability among locations and a high degree of variability within locations would result if the primary source of inoculum was airborne ascospores, which would be dispersed uniformly within the field. This finding was confirmed by gametic disequilibrium analysis and suggests that the sexual reproduction of M. graminicola occurs in Saskatchewan.

Diet, obesity and education in three age groups of Saskatchewan women.

Research on relationships between socioeconomic status and Canadians' diet is limited. The current study investigated differences by education in dietary variables shown to be related to obesity; it included three age groups of Saskatchewan women who participated in the 1992 to 1993 Heart Health Intervention Evaluation baseline study. Multistage sampling was used to select randomly from the Saskatchewan Health Insurance Registration File. The overall response rate was 42.6%; a sample representative of the general Saskatchewan population was obtained. Three-day estimated food records and demographic information from 396 women aged 18 to 74 years were subdivided into three age categories: 18 to 34 years, 35 to 54 years, and 55 to 74 years. For the 18- to 34-year group, obesity was significantly more prevalent with lower education; trends were similar for the older age groups. Under-reporting of energy intake (indicated by an energy intake:basal metabolic rate ratio of <1.1) was related to obesity but not to education. The greatest differences in diet between educational groups were observed in the 18- to 34-year group; fewer differences existed in the 35- to 54-year group, and none in the 55- to 74-year group. Health promotion efforts need to be targeted appropriately, and based on differences in dietary intakes by socioeconomic group. Research should help promote an understanding of the reasons for differences in diet by socioeconomic status.

Pilot-Scale Evaluation of Select Nitrate Removal Technologies

Due to the extensive application of artificial nitrogen-based fertilizers and animal manure on land, many water agencies face problems of increasing concentrations of nitrate in groundwater. The contamination of groundwater by nitrate may pose a significant public health problem. The threat of methemoglobinemia is well documented and reflected in the US drinking water standard of 10 mg/L as nitrate-nitrogen. Approximately 45% of Saskatchewan's population use groundwater for drinking purposes, out of which, approximately 23% (230,000) are rural residents. The water used is made available from over 48,000 privately owned wells in regions where there is an extensive application of chemical fertilizers. Biological denitrification, ion exchange, and reverse osmosis (RO) processes were selected for a field study. Field studies were conducted on these processes. The sulfur/limestone autotrophic denitrification (SLAD) process was selected to achieve biological removal of nitrate from groundwater. The feasibility of the system was evaluated under anaerobic conditions. An ion exchange study was conducted using Ionac A554 which is a strong anion exchange resin. In the case of groundwater containing low sulfate concentrations, A554 offered high nitrate removal. However, the disposal of regenerant brine can be a problem. A reverse osmosis unit with Filmtec membrane elements (FT30-Element Family) was used in the study on nitrate removal. The unit effluent average nitrate concentration was less than the maximum allowable concentration.

Stabilization of an Increasing Trend in Physician-Diagnosed Asthma Prevalence in Saskatchewan, 1991 to 1998

To determine the prevalence of asthma, bronchitis, and COPD using the physician services database of the Saskatchewan Health Department from 1991 to 1998. Descriptive population-based study. The Province of Saskatchewan, Canada. Residents of Saskatchewan covered by universal health care in the province. In all age groups, asthma prevalence increased between 1991 and 1995 and either was stable or declined between 1996 and 1998. Preschool children had the highest asthma prevalence during the study period, followed by children aged 5 to 14 years, young adults aged 15 to 34 years, and adults aged 35 to 64 years. Children aged 0 to 4 years and adults aged 35 to 64 years in the Registered Indian population had greater asthma prevalence than persons in other urban or rural populations during the study period. Asthma prevalence rates in rural populations were less than or similar to the rates of urban populations in all age groups during the study period. The prevalence of bronchitis was greater in the Registered Indian population than in urban and rural populations in all age groups throughout the study period. When persons who had visited a physician for bronchitis were excluded from the prevalence calculation, the original increases seen in asthma prevalence among very young children and older adults of Registered Indian origin disappeared, with the urban population having greater asthma prevalence in all age groups. In the Registered Indian population, adults aged 35 to 64 years had almost twofold increases in the prevalence of COPD in comparison to other Saskatchewan populations. Asthma prevalence, which had been on the increase in the 1980s and early 1990s, was either stable or declining during the latter part of 1990s in Saskatchewan. Preschool children and older adults from the Registered Indian population had greater asthma prevalence than did those from other Saskatchewan populations. Asthma prevalence among the rural populations was either similar or lower in comparison to the rates for the urban populations in all age groups during the study period. Further research is required to elucidate the findings in this study.

Physiologic specialization of Puccinia graminis on wheat, barley, and oat in Canada in 2000

Stem rust is a devastating disease of cereal crops that is currently controlled, in Canada, primarily through the use of resistant cultivars. Annual surveys are conducted throughout Canada to monitor rust severity and obtain rust collections that are used to determine the virulence spectrum of each pathogen population. This is necessary for the detection of novel races that may express high virulence to currently grown cereal cultivars and to identify changes in virulence in the pathogen population. No stem rust was observed on cultivated spring wheat in 2000. Stem rust severity was light (<5%) on barley and oat in Manitoba, eastern Saskatchewan, and Ontario in 2000 and stem rust was not detected in other regions. Stem rust samples were collected from Hordeum jubatum, Avena fatua, and trap-plot nurseries and commercial fields of wheat, barley, and oat in Manitoba, eastern Saskatchewan, and Ontario from June to September 2000. Eight races of Puccinia graminis f. sp. tritici were found in collections from wheat, 11 from cultivated barley, and 2 from wild barley, with RCRSK as the dominant race on all three hosts. However, a cluster of races (QCCJ_, RCCJ_, and RMCJ_) with virulence to cultivated barley composed 69.2% of the population in Manitoba and Saskatchewan and poses a threat to barley production in this region. Five races of P. graminis f. sp. avenae were found in collections from cultivated oat and six from wild oat. Races NA67 and NA29 were the most common on cultivated (52.2 and 30.4%, respectively) and wild (18.6 and 55.0%, respectively) oat, while NA76 increased in frequency (9.6%) in Manitoba and Saskatchewan in 2000. Races NA67 and NA76 are virulent to Pg2, Pg9, and Pg13, which are the resistance genes likely present in most currently grown Canadian oat cultivars, and threaten commercial oat production in this region.

NESTING ECOLOGY OF MIXED-GRASS PRAIRIE SONGBIRDS IN SOUTHERN SASKATCHEWAN

During 1996–2000, I studied the nesting ecology of Sprague's Pipits (Anthus spragueii), Clay-colored Sparrows (Spizella pallida), Savannah Sparrows (Passerculus sandwichensis), Baird's Sparrows (Ammodramus bairdii), Chestnut-collared Longspurs (Calcarius ornatus), and Western Meadowlarks (Sturnella neglecta) on 47 native mixed-grass prairie pastures in southern Saskatchewan. Predation was the primary cause of nest failure and occurred at a similar frequency among the six species. Nest success and productivity varied among years and was lowest during 1997, the year of a substantial increase in meadow vole (Microtus pennsylvanicus) populations in southern Saskatchewan. Nest predation was most severe during the nestling stage with daily survival rates typically lower than those of the incubation period. Brown-headed Cowbirds (Molothrus ater) parasitized nests of all six species, with 5–29% of host nests containing cowbird eggs. Savannah Sparrows, Clay-colored Sparrows, and Western Meadowlarks incurred the highest frequency of brood parasitism. Parasitized hosts experienced lower productivity due to a combination of reductions in clutch size, hatching success, and fledging success. Overall, brood parasitism by cowbirds cost these birds between 1.3 and 2.2 young per successful nest. These results support the general contention that nest predation is the primary factor influencing grassland songbird reproductive success.

Statin use and the risk of breast cancer

The study objective was to investigate a possible association between statin use and breast cancer (BRCA). An historical cohort design based on Saskatchewan's population health services databases was used. All eligible women with ⩾1 statin prescription from 1989 to mid-1997 and an age–sex-matched nonexposed group were followed up to 8.5 years (mean 4.2 years). Relative rates (RR) of BRCA were estimated and stratified by age, statin exposure time, and prior hormone use. Thirteen thousand five hundred ninety-two statin users and 53,880 nonexposed subjects were identified. Eight hundred seventy-nine incident BRCA cases were identified. Statins were not associated with BRCA risk in women ⩽55 years. Among subjects >55 years, the RR for BRCA was 1.15 (0.97, 1.37). Stratified analyses revealed increases in risk in short-term statin users and statin users with long-term hormone replacement therapy (HRT) exposure. More studies are needed to determine if short-term statin use and statin use with long-term HRT exposure increases postmenopausal BRCA risk. Published by Elsevier Science Inc.

Antihypertensive drug therapy in Saskatchewan: patterns of use and determinants in hypertension.

The benefits of continuous treatment of hypertension have been extensively documented in randomized controlled trials. However, clinical trials may not reflect actual drug use in the population. To examine the distribution and determinants of patterns of use of antihypertensive agents in the first 5 years of hypertension treatment in Saskatchewan. Patterns of use and modifications to therapy were derived from a careful examination of medication use in a cohort of 19 501 subjects aged 40 to 79 years, without recognized cardiac disease and initiating therapy with an angiotensin-converting enzyme inhibitor, a calcium antagonist, or a beta-blocker in Saskatchewan between 1990 and 1993. Angiotensin-converting enzyme inhibitors (37.4%), followed by calcium antagonists (27.5%) and beta-blockers (26.4%), were the most commonly prescribed agents to initiate treatment in our study population. Patients with diabetes were less likely to be dispensed a beta-blocker, as were younger and female patients. Previous visits to a cardiologist decreased the likelihood of receiving combination therapy or angiotensin-converting enzyme inhibitors but increased that of using calcium antagonists. Apart from dose adjustment, 89% of study subjects underwent at least 1 modification to their initial regimen, at a median time of 134 days. After 1 year, only 33.8% of patients were still using their initial drug. An early decrease in the proportion of patients continuing to receive initial therapy was noted, especially among beta-blocker users. Erratic drug-taking behaviors were observed in this Saskatchewan population. In addition, initial drug use does not seem to be in accordance with the stepped-care approach to hypertension therapy recommended in the Canadian guidelines.

The Roots of North America's First Comprehensive Public Health Insurance System

askatchewan, sandwiched between Alberta and Manitoba, is one of three prairie provinces in Canada. The province consists mainly of dry prairie in the south (where it borders the states of Montana and North Dakota) and subArctic forest, giving away to tundra along its border with the North West Territories. It was opened for European settlement after the building of the Canadian Pacific Railway at the end of the nineteenth-century and grew slowly, stabilizing at a population of between 900,000 and one million after the 1940s. Until the 1950s, this sparsely settled province was sustained by a one-crop wheat economy. Saskatchewan's population distribution reflected this, as most people lived in rural areas. There were only two medium-sized cities (Regina and Saskatoon) and six smaller ones ‘which anchored a network of villages and towns that covered an expanse of agricultural land larger than France’. Although less than eight per cent of Canadians lived in Saskatchewan in the 1940s, this province has played a large role in the development of national social policy. Western Canada, particularly Saskatchewan and Manitoba, was the crucible of the nation's Social Democratic movement which was based largely on the strong tradition of co-operative prairie wheat farming and marketing. Canada's first Social Democratic party, the Cooperative Commonwealth Federation (CCF), the forerunner of the New Democratic Party, was born during the Great Depression in Manitoba and Saskatchewan. The party came to power in the Saskatchewan pro-

Systemic lupus erythematosus and the risk of malignancy.

The objective of this study was to determine the relative risks of malignancy and of site-specific malignancies in patients with systemic lupus erythematosus (SLE). A cohort of 297 patients (91% Caucasian) with SLE were seen between 1975 and 1994 and followed for a mean of 12 years at the University of Saskatchewan Rheumatic Disease Unit. Expected cancer incidence rates were determined based on Province of Saskatchewan population statistics matched to each study patient for age, sex and calendar year of follow-up. Standardized incidence ratios (SIRs) of observed to expected cancers and 95% confidence intervals (95% CI) were calculated. A total of 27 cases of cancer were observed, whereas only 16.9 were expected (SIR 1.59 (95% CI 1.05-2.32)). For site-specific malignancies, an excess of cancer of the cervix (SIR 8.15 (95% CI 1.63-23.81)) as well as hemopoietic malignancy (SIR 4.9 (95% CI 1.57-11.43)) was found. The hemopoietic cancers were predominantly non-Hodgkin's lymphoma (SIR 7.01 (95% CI 1.88-17.96)). We did not find an association of malignancy with known risk factors, including use of cytotoxic agents. Increased risk of malignancy, notably non-Hodgkin's lymphoma and perhaps cervical cancer, should be regarded as a complication of SLE.

International governance and reform of the World Trade Organization.

Excerpts of a Brief prepared for the "Genoa Non-Governmental Initiative" for the International Union for Health Promotion and Education, by Ronald Labonte, Member, IUHPE Working Groups on Advocacy and Social Clauses; and Director, Saskatchewan Population Health and Evaluation Research Unit, and Professor, Universities of Saskatchewan and Regina, Canada.

The Factors Associated With Neck Pain and Its Related Disability in the Saskatchewan Population

Population-based, cross-sectional mailed survey. To identify factors associated with neck pain and its related disability in Saskatchewan adults. Little is known about the etiology of neck pain and its related disability. Previous cross-sectional population-based studies have suggested that neck pain may be associated with age, female gender, lower socioeconomic status, physically demanding work, and other comorbidities. The Saskatchewan Health and Back Pain Survey was mailed to 2184 randomly selected Saskatchewan adults 20 to 69 years of age. Fifty-five percent of the study population participated. The survey collected demographic, socioeconomic, and health-related information. Neck pain and its related disability was classified into four categories using the Chronic Pain Questionnaire: no neck pain (Grade 0), low intensity/low disability neck pain (Grade I), high intensity/low disability neck pain (Grade II), and high disability neck pain (Grades III-IV). Polytomous logistic regression was used to identify associations between demographic, socioeconomic, and health-related variables and various grades of neck pain severity. Of the 1131 respondents, 54% had experienced neck pain at some point in the 6 months before the survey, and almost 5% were highly disabled by neck pain. The prevalence of Grade I neck pain was lower in individuals with low education attainment, but higher for those reporting headaches, low back pain, better general health, and a history of neck injury resulting from a motor vehicle collision, some of whom may have received compensation for their injury. Grade II neck pain was strongly associated with headache, low back pain, and a history of neck injury during a motor vehicle collision and weakly associated with digestive disorders and current cigarette smoking. Grades III-IV neck pain was strongly associated with low back pain, headaches, cardiovascular disorders, digestive disorders, and a history of neck injury during a motor vehicle collision. This study suggests that important associations exist between comorbidities, a past history of neck injury resulting from a motor vehicle collision, and graded neck pain. Importantly, individuals who are significantly disabled by neck pain also have comorbidities that have a moderate or severe impact on their health, suggesting that chronic disorders tend to cluster in some individuals.

Generalizing the results of clinical trials to actual practice: the example of clopidogrel therapy for the prevention of vascular events

PURPOSE: An important element in translating the results obtained in clinical trials of a new treatment to clinical practice is the estimated event rate in patients who would be eligible to receive that treatment. We estimated the effect of clopidogrel, compared with aspirin, in actual practice using the relative risk reduction observed in the Clopidogrel versus Aspirin in Patients at Risk of Ischaemic Events (CAPRIE) trial. SUBJECTS AND METHODS: Ischemic event rates were estimated for 12,931 aspirin users drawn from the Saskatchewan Health population between 1990 and 1995 who had an index diagnosis of myocardial infarction, ischemic stroke, or peripheral arterial disease. To estimate the absolute risk reduction, the 8.7% relative risk reduction from clopidogrel compared with aspirin that was observed in CAPRIE was applied to these rates. RESULTS: The rates of ischemic events were greater in actual practice than among the control patients in the CAPRIE trial. In the Saskatchewan population, patients experienced an outcome event (myocardial infarction, stroke including intracranial hemorrhage, or death) at a rate of 15.9 per 100 patient-years, compared with only 6.9 per 100 patient-years in CAPRIE. If the same 8.7% relative risk reduction seen in the CAPRIE trial is also true for patients seen in routine clinical practice, the greater absolute risk in actual practice would reduce the number needed to treat to prevent one event from 200 patients to 70 patients. CONCLUSION: Absolute risk rates may be substantially greater in clinical practice than in the selected patients enrolled in randomized trials. As a result, similar reductions in relative risk, if true for clinical practice, may yield substantially more benefit in clinical practice than in randomized trials.

Virulence dynamics, phenotypic diversity, and virulence complexity in two populations of Puccinia triticina in Canada from 1987 to 1997

Populations of Puccinia triticina (causal agent of wheat leaf rust) in Ontario, Quebec, Manitoba, and Saskatchewan were analysed for frequency of isolates with virulence to leaf rust resistance genes Lr1, Lr2a, Lr2c, Lr3, Lr9, Lr16, Lr24, Lr26, Lr3ka, Lr11, Lr17, and Lr30 for the years 1987-1997. Winter wheats in the southern plains of the United States with resistance genes Lr24, Lr26, Lr11, Lr3ka, Lr17, and Lr16 selected virulent P. triticina phenotypes in the Manitoba and Saskatchewan population. The P. triticina population in Quebec and Ontario was comparatively stable, showing no directional trends in selection of virulence phenotypes. In the Manitoba and Saskatchewan population, diversity of virulence phenotypes changed relatively little despite the selection that occurred in this population. The average number of virulences per isolate in the Manitoba and Saskatchewan population increased from 1987 to 1994 during the period of selection for virulence to Lr24, Lr26, Lr3ka, and Lr11, and declined from 1995 to 1997 when selection for virulence to Lr16 and Lr17 occurred. The most complex virulence phenotypes were not necessarily selected in the Manitoba and Saskatchewan population because of how the resistance genes were deployed in the host population and the nonrandom distribution of virulences in the P. triticina population.Key words: Puccinia recondita f.sp. tritici, specific resistance, wheat leaf rust, Triticum aestivum, specific virulence.

The American elm and Dutch elm disease

Shortly after World War I, a new disease previously unknown among elms emerged in Holland. It spread rapidly from Europe to Great Britain (1927), United States (1930), and Canada (1945), killing millions of elms. The disease known, as Dutch elm disease (DED) is a wilt disease, caused by the fungus Ophiostoma ulmi. It is transmitted from tree to tree by elm bark beetles (scolytid) vectors. Numerous attempts to control the disease have concentrated on the reduction of insect vector populations, exploitation of natural host resistance, extensive application of fungicides and integrated pest management. In spite of these efforts in Canada, the disease continues to migrate westwards threatening the elm populations in Saskatchewan and Alberta. Today there are approximately 700 000 elm shade trees in cities and towns across Canada and their value exceeds $2.5 billion dollars.With the advance of molecular biology new, powerful tools are now available to study, in greater detail, the molecular and biochemical mechanisms of the DED pathogen, with particular reference to the mechanisms that induce host defenses. A glycoprotein has been isolated and identified such that when injected either in liquid or pellet form into the elm tree, significantly reduced the wilting symptoms of both five-year old elm seedlings and 10 cm diameter trees. The elicitor induces a chain of defensive reactions that prevent the rapid spread of the fungus within the vascular system of the host. Key words: Ophiostoma ulmi, elm bark beetle vectors, induced resistance, chemical control, RFLP, mitochondrial DNA, ribosomal DNA, virus-like DNA, resistance breeding

The Saskatchewan health and back pain survey. The prevalence of low back pain and related disability in Saskatchewan adults.

Population-based, cross-sectional, mailed survey. To determine the lifetime, 6-month period, and point prevalence of low back pain and its related disability among Saskatchewan adults and to investigate the presence and strength of selective response bias. There have been many reports of the prevalence of low back pain in different populations, and the estimates vary widely depending on case definition. However, most studies fail to differentiate between trivial and disabling back pain, which raises the issue of the usefulness of these estimates. No studies have yet documented the prevalence of graded low back pain severity and its related disability in a North American, general, population-based survey. The Saskatchewan Health and Back Pain Survey was mailed to a probability sample of 2184 Saskatchewan adults between 20 and 69 years of age. Fifty-five percent of the eligible population responded to the survey. Respondents were compared with nonrespondents, and the presence of selective response bias by back pain status was investigated by wave analysis. The point and lifetime prevalence of low back pain was determined by simple questions, and the 6-month period prevalence of low back pain was determined by the Chronic Pain Questionnaire. All estimates were age standardized to the Saskatchewan population. The authors estimate that at the time of the survey 28.4% (95% confidence interval, 25.6-31.1) of the Saskatchewan adult population were experiencing low back pain, and 84.1% (95% confidence interval, 81.9-86.3) had experienced it during their lifetime. Overall, 48.9% (95% confidence interval, 45.9-52.0) of the population had experienced low intensity/low-disability low back pain in the previous 6 months, 12.3% (95% confidence interval, 10.3-14.4) had experienced high-intensity/low-disability low back pain, and an additional 10.7% (95% confidence interval, 8.8-12.5) had experienced high-disability low back pain in the previous 6 months. There was little variation in the estimates over age groups, but women experienced more high-disability back pain than men. There was no evidence of selective response bias by low back pain status in the survey. Low-intensity/low-disability low back pain is a common problem in the general population. Approximately 11% of the adult population studied had been disabled by low back pain in the previous 6 months.

Rheumatoid arthritis and the risk of malignancy.

To determine the relative risks of malignancy and of site-specific malignancies in patients with rheumatoid arthritis (RA). In a prospective cohort study, 862 patients with RA (96% white) were enrolled from 1966 to 1974 and were followed up for up to 35 years (mean 17.4 years) at the University of Saskatchewan Rheumatic Disease Unit. All diagnoses of cancer were cross-referenced with the Provincial Cancer Registry. Expected cancer incidence rates were determined based on province of Saskatchewan population statistics matched to each study patient for age, sex, and calendar year. Standardized incidence ratios (SIRs) of the observed-to-expected cancer incidence and 95% confidence intervals (95% CI) were then calculated. A total of 136 cases of cancer were observed compared with 168 expected (SIR 0.80, P = 0.011 [95% CI 0.67-0.95]). The relative risk of colorectal malignancy was significantly reduced in the RA study population (SIR 0.52, P = 0.037 [95% CI 0.25-0.96]). A significant excess of leukemia was found (SIR 2.47, P = 0.026 [95% CI 1.12-4.69]), whereas the incidence rates for Hodgkin's disease and non-Hodgkin's lymphoma and all other site-specific malignancies were not found to be significantly different from general population rates. In our cohort of RA patients, colorectal cancer was detected in only half the expected number of patients. This risk reduction may be related to long-term nonsteroidal antiinflammatory drug (NSAID) use in RA, as has been suggested in several other studies of long-term NSAID use. An increased risk of leukemia was confirmed. This may be due to the persistent immune stimulation associated with RA itself, since other potential explanatory factors for increased leukemia were not apparent. Despite the excess of hemopoietic malignancy and despite treatment of RA with potentially oncogenic agents, the overall risk of malignancy was reduced in this RA cohort.

The Red Fox Invasion and Other Changes in Wildlife Populations in West-Central Saskatchewan Since the 1960s

The Red Fox Invasion and Other Changes in Wildlife Populations in West-Central Saskatchewan Since the 1960s