Mortality of Canadians treated by peritoneal dialysis in remote locations

Patients residing in remote locations may be more likely to initiate peritoneal dialysis when starting renal replacement therapy to avoid relocation. These patients may have reduced access to medical care, however. To examine the hypothesis that patients residing some distance from their nephrologists would be more likely to select peritoneal dialysis but have an increased risk of mortality, we used prospectively collected data in a random sample of 26,775 patients initiating dialysis in Canada between 1990 and 2000. The distance between the patient's residence at dialysis inception and the practice location of their nephrologists was calculated. We used Cox proportional hazard models to determine the adjusted relation between this distance and clinical outcomes over a mean follow-up period of 2.5 years up to 14 years. Remote-dwelling patients were more likely than urban dwellers to commence peritoneal dialysis in distances ranging from 50 to greater than 300 km than those residing within 50 km. The adjusted rates of death and the adjusted hazard ratio among patients initiating peritoneal dialysis was significantly higher in those living further from the nephrologists than those living within 50 km. Further study into the quality of care delivered to remote-dwelling patients on peritoneal dialysis is needed.

Patient and allograft survival of Indo Asian and East Asian dialysis patients treated in Canada

Kidney failure is relatively common among Canadians of Asian origin. However, little is known about the health outcomes after initiation of renal replacement therapy in this population. Our study evaluates differences in the likelihood of renal transplantation and graft loss among Asian and white patients. We studied 21 523 adults of East Asian, Indo Asian or white ethnicity who had initiated dialysis in Canada from 1990-2000. Subjects were followed until death, loss to follow-up or end of study (2004). The proportion of the eligible subjects who were East Asian, Indo Asian, or white was 6, 3, and 91%, respectively. Compared to white patients, East Asian and Indo Asian patients were significantly less likely to receive a renal transplant after adjusting for potential confounding factors. This disparity is greater for transplants from living donors as compared to those from deceased donors. The adjusted death censored graft loss in transplant recipients was not significantly different between ethnic groups. The adjusted risk of death following transplantation, however, was significantly lower in Indo Asian than in white patients. Our findings show that in a Canadian population, patients of East Asian or Indo Asian origin had lower rates of renal transplantation than white patients, especially for living donor transplantation. These findings warrant further study, especially given the good graft outcomes in these individuals.

Association between residence location and likelihood of kidney transplantation in Aboriginal patients treated with dialysis in Canada

For reasons that are not well understood, Aboriginal people with end-stage renal disease (ESRD) have lower rates of kidney transplantation. We hypothesized that distance between residence location and the closest transplant center was greater in Aboriginal dialysis patients and would partially explain the lower rate of transplantation in this population. We studied a random sample of 9905 patients initiating dialysis in Canada between 1990 and 2000. We calculated the distance between residence location at dialysis inception and the closest transplant center. Cox proportional hazards models were used to examine the relation between residence location and the likelihood of transplantation over a median period of 2.3 years. The proportion of Aboriginal participants living <or=50, 50.1-150, 150.1-300, and >300 km from the closest transplant center was 25, 18, 18, and 39% respectively, compared with 55, 19, 11, and 15% among white subjects. The relative likelihood of transplantation was significantly lower for Aboriginal compared to white participants across all four distance strata, with no apparent effect of residence location. For example, the relative likelihood of transplantation was hazard ratio (HR) 0.47, 95% confidence interval (CI) (0.31-0.72) in Aboriginal participants residing <or=50 and 0.55 (0.38-0.80) in those residing >300 km from the closest transplant center. Results were similar for transplants from deceased donors and living donors, and in all seven regions studied. In conclusion, remote location of residence does not explain the lower rate of kidney transplantation among Aboriginal people treated for ESRD in Canada.

Airway function among Inuit primary school children in far northern Quebec

The study of the prevalence and determinants of asthma and allergy in different populations may provide clues to their etiology. We describe airway function and its determinants among Inuit schoolchildren living in far Northern Quebec. We assessed the presence of airways hyperresponsiveness (AHR), defined as a 15% drop in FEV1 with exercise, airflow obstruction, as judged by a reduced FEV1/FVC, and atopy, as evidenced by skin test positivity to inhaled aeroallergens, among 509 Inuit aged mostly from 6 to 13 yr. Smoking by the children (31.9%) and their parents was common, including maternal smoking during pregnancy (79.5%). Atopy was found in only 5.3% of children. Apart from age, there were no significant associations between AHR and any of the determinants examined. Airflow obstruction was present among 7.7% of children and occurred most commonly among children with higher levels of salivary cotinine and in those with four or more lower respiratory illnesses in the first 2 yr of life. Asthma and atopy were uncommon in this population whereas evidence of chronic airflow obstruction was frequently found. Measures to reduce the spread of respiratory infection and prevention of smoking are likely to be of most benefit in improving respiratory health in these isolated communities.

Benzodiazepine use and the risk of motor vehicle crash in the elderly

CONTEXT

Benzodiazepines, used by a sizable number of the elderly population, may affect the ability to drive and thus increase the risk of a motor vehicle crash. Epidemiologic studies of this question have produced inconsistent results that may be due to the different effects of long- and short-half-life benzodiazepines and variations in their duration of use.

OBJECTIVE

To determine whether the use of benzodiazepines of either long- or short-elimination half-life is associated with the risk of injurious motor vehicle crash in the elderly.

DESIGN AND SETTING

Nested case-control design within a cohort of 224,734 drivers from the Canadian province of Quebec, aged 67 to 84 years, followed up from 1990 to 1993. Computerized data for the study were obtained from provincial driver's license files, police reports of injurious crashes, and health insurance records.

PATIENTS

We identified all 5579 drivers involved in an injurious crash (cases) and a random sample of 10 controls per case selected from a subcohort of 13,256 subjects.

MAIN OUTCOME

Involvement of a cohort member as a driver in a motor vehicle crash in which at least 1 person (not necessarily the driver) sustained bodily injury.

RESULTS

The adjusted rate ratio of crash involvement within the first week of long-half-life benzodiazepine use was 1.45 (95% confidence interval [CI], 1.04-2.03). The rate ratio for continuous use of longer duration up to 1 year was slightly lower but remained significant (rate ratio, 1.26; 95% CI, 1.09-1.45). In contrast, there was no increased risk after the initiation of treatment with short-half-life benzodiazepines (rate ratio, 1.04; 95% CI, 0.81-1.34) or with their continued use (rate ratio, 0.91; 95% CI, 0.82-1.01).

CONCLUSIONS

Brief or extended periods of exposure to long-half-life benzodiazepines are associated with an increased risk of motor vehicle crash involvement in the elderly population. There is no such elevated risk for short-half-life benzodiazepines.

Bronchodilators and acute cardiac death

Bronchodilators used in the treatment of airway disease have been shown to have a variety of cardiac effects that may contribute to the occurrence of life-threatening events such as cardiac arrhythmias and cardiac arrest. We investigated whether theophylline and beta-agonists were associated with cardiovascular mortality among a cohort of subjects prescribed antiasthma medications. We used a population-based cohort of 12,301 subjects aged 5 to 54 yr, formed from health-insurance data bases from Saskatchewan, Canada, and spanning the period 1978 to 1987. Within this cohort, we identified all 30 deaths from cardiovascular causes in which acute asthma did not appear to be a contributing factor. We identified all asthma and cardiovascular drugs dispensed to these subjects shortly before their deaths and compared this therapy to that dispensed to a random sample of 4,080 person-time controls. After adjustment for age and the prior use of cardiac drugs, the rate of cardiovascular death was greater in users of theophylline, with a rate ratio (RR) of 2.7 (95% Cl:1.2 to 6.1), and in users of beta-agonists taken orally or by nebulizer (RR = 2.4; 95% Cl:1.0 to 5.4), but not in users of beta-agonists administered by metered-dose inhaler (RR = 1.2; 95% Cl:0.5 to 2.7). The great majority of cardiovascular deaths occurred among subjects with clinical or pathologic evidence of potentially lethal conditions. These results suggest that the use of theophylline and of beta-agonists administered orally or by nebulization should be avoided in subjects with significant cardiac disease or at high risk for such disease, especially acute coronary insufficiency and congestive cardiomyopathy. On the other hand, the use of beta-agonists administered by metered-dose inhalers (MDIs) was not associated with an increased risk of cardiovascular death.

Is the association between inhaled beta-agonist use and life-threatening asthma because of confounding by severity?

We have previously reported an increasing dose-response relationship between the regular use of beta-agonist inhalers and the risk of asthma death and near death among a cohort of 12,301 subjects who had been dispensed 10 or more prescriptions of asthma drugs from January 1980 to April 1987. That analysis was based solely on information obtained from linkable computerized data bases. Such an association might be explained in part by the tendency of patients with more severe asthma, that is, those at greatest risk for an adverse outcome, to use more beta-agonist medication. To further examine this potential confounding by severity, we gathered clinical information independently from the field on the 129 case patients and their 655 control patients from the matched case-control analysis of 12,301 subjects. In 68% of the control patients with a life-threatening episode and 75% of the matched control subjects, we obtained a valid questionnaire from at least one physician who had seen the patient during the previous 2 yr. Acceptable information on hospitalizations because of asthma was obtained in 87% of those hospitalized. Clinical features associated with an increased risk of fatal and near-fatal asthma were: a history of loss of consciousness or seizures during a previous asthma attack (odds ratio, 10.2; 95% CI, 3.9 to 26.7), a history of attacks of asthma precipitated by eating certain foods (odds ratio, 5.1; 95% CI, 2.4 to 11.1), a clinical score designed to reflect the severity of prior attacks of asthma leading to hospitalization, and prior respiratory acidosis among those in whom a blood gas determination was recorded.(ABSTRACT TRUNCATED AT 250 WORDS)

Use of gastrointestinal and respiratory illness hospitalization rates as indicators of different social influences

The hospitalization rates for gastrointestinal and respiratory illnesses in children under five years of age were examined on two Indian reserves in Northern Saskatchewan. The gastrointestinal illness rate was used as an index of waterborne disease, and the respiratory rate as an index of general health and of local customs affecting hospitalizations. The reserve rates were compared with those for other Saskatchewan status Indians and for other Saskatchewan residents. The risk ratios between the reserves and other Indians, and between the reserves and other Saskatchewan residents, were increased for both gastrointestinal and respiratory illnesses. The risk ratio of gastrointestinal rate divided by respiratory rate was greater for either reserve than for other Indians or other Saskatchewan residents. Waterborne illnesses were an even greater problem on the two study reserves than on other reserves. Comparing hospitalization rates for different illness groups is a useful method to compare the effect of different social factors.

Clinical complexity and epidemiologic uncertainty in case-control research. Fenoterol and asthma management

Two recent epidemiologic case-control studies suggested that fenoterol, a selective beta-adrenergic agonist, was associated with an increase in the risk of asthma death. The results of these studies were criticized because of methodologic problems in the choice and selection of control subjects; the different methods used to gather exposure data in cases and control subjects; and because of inadequate classification and adjustment for asthma severity. In response to this controversy, a new study is underway, the Saskatchewan Asthma Epidemiology Project. The SAEP includes two complementary studies, an historic cohort and a case-control analysis, that employ the computerized databases of the Saskatchewan Health Department. A unique aspect of the SAEP is the attempt to incorporate knowledge of asthma physiology and management into the design of the studies. Specifically, the study design recognized the role of antiinflammatory drugs in asthma treatment; the distinction between asthma death and near-fatal asthma; the severity of asthma; patterns of drug use; and the distinction between inadequate clinical care and disease severity. The strategies we employed in the SAEP may prove helpful to investigators whenever clinical and biologic processes create sources of potential bias requiring special procedures for the design and analysis of epidemiologic studies.