Donald A. Redelmeier

ASSOCIATION BETWEEN CELLULAR-TELEPHONE CALLS AND MOTOR VEHICLE COLLISIONS

BACKGROUND Because of a belief that the use of cellular telephones while driving may cause collisions, several countries have restricted their use in motor vehicles, and others are considering such regulations. We used an epidemiologic method, the case-crossover design, to study whether using a cellular telephone while driving increases the risk of a motor vehicle collision. METHODS We studied 699 drivers who had cellular telephones and who were involved in motor vehicle collisions resulting in substantial property damage but no personal injury. Each persons cellular-telephone calls on the day of the collision and during the previous week were analyzed through the use of detailed billing records. RESULTS A total of 26,798 cellular-telephone calls were made during the 14-month study period. The risk of a collision when using a cellular telephone was four times higher than the risk when a cellular telephone was not being used (relative risk, 4.3; 95 percent confidence interval, 3.0 to 6.5). The relative risk was similar for drivers who differed in personal characteristics such as age and driving experience; calls close to the time of the collision were particularly hazardous (relative risk, 4.8 for calls placed within 5 minutes of the accident, as compared with 1.3 for calls placed more than 15 minutes before the accident; P<0.001); and units that allowed the hands to be free (relative risk, 5.9) offered no safety advantage over hand-held units (relative risk, 3.9; P not significant). Thirty-nine percent of the drivers called emergency services after the collision, suggesting that having a cellular telephone may have had advantages in the aftermath of an event. CONCLUSIONS The use of cellular telephones in motor vehicles is associated with a quadrupling of the risk of a collision during the brief time interval involving a call. Decisions about regulation of such telephones, however, need to take into account the benefits of the technology and the role of individual responsibility.

When More Pain Is Preferred to Less: Adding a Better End

Subjects were exposed to two aversive experiences: in the short trial, they immersed one hand in water at 14 °C for 60 s; in the long trial, they immersed the other hand at 14 °C for 60 s, then kept the hand in the water 30 s longer as the temperature of the water was gradually raised to 15 °C, still painful but distinctly less so for most subjects. Subjects were later given a choice of which trial to repeat. A significant majority chose to repeat the long trial, apparently preferring more pain over less. The results add to other evidence suggesting that duration plays a small role in retrospective evaluations of aversive experiences; such evaluations are often dominated by the discomfort at the worst and at the final moments of episodes.

The Treatment of Unrelated Disorders in Patients with Chronic Medical Diseases

BACKGROUND Patients can have several illnesses concurrently, yet some of these diseases may be neglected if one problem consumes attention. We conducted a population-based analysis in Ontario, Canada - where universal health insurance is provided - to determine whether unrelated disorders are less likely to be treated in patients with chronic diseases. METHODS We studied the 1,344,145 residents of Ontario in 1995 who were 65 or older and eligible to receive prescription medications free of charge as part of the Ontario Drug Benefit program. Patients with diabetes mellitus were identified by prescriptions for insulin, pulmonary emphysema by prescriptions for ipratropium bromide, and psychotic syndromes by prescriptions for haloperidol. For each chronic disease, we selected an unrelated treatment: estrogen-replacement therapy for patients with diabetes mellitus, lipid-lowering medications for those with pulmonary emphysema, and medical treatment of arthritis for those with psychotic syndromes. RESULTS The 30,669 patients with diabetes mellitus were less likely to receive estrogen-replacement therapy than the other subjects in the study (2.4 percent vs. 5.9 percent, P<0.001). The disease was associated with a 60 percent reduction in the odds of estrogen treatment (odds ratio, 0.40; 95 percent confidence interval, 0.37 to 0.43). Findings were similar for the 56,779 patients with pulmonary emphysema, who were less likely to receive lipid-lowering medications (odds ratio, 0.69; 95 percent confidence interval, 0.67 to 0.72; P<0.001), and the 17,336 patients with psychotic syndromes, who were less likely to receive medical treatments for arthritis (odds ratio, 0.59; 95 percent confidence interval, 0.57 to 0.62; P<0.001). CONCLUSIONS In patients 65 or older who have chronic medical diseases and who receive prescription medications free of charge, unrelated disorders are undertreated. Clinicians caring for patients with chronic diseases should remain alert to other disorders and minimize the number of missed opportunities for treating them.

Cardiovascular health after maternal placental syndromes (CHAMPS): population-based retrospective cohort study

BACKGROUND Maternal placental syndromes, including the hypertensive disorders of pregnancy and abruption or infarction of the placenta, probably originate from diseased placental vessels. The syndromes arise most often in women who have metabolic risk factors for cardiovascular disease, including obesity, pre-pregnancy hypertension, diabetes mellitus, and dyslipidaemia. Our aim was to assess the risk of premature vascular disease in women who had had a pregnancy affected by maternal placental syndromes. METHODS We did a population-based retrospective cohort study in Ontario, Canada, of 1.03 million women who were free from cardiovascular disease before their first documented delivery. We defined the following as maternal placental syndromes: pre-eclampsia, gestational hypertension, placental abruption, and placental infarction. Our primary endpoint was a composite of cardiovascular disease, defined as hospital admission or revascularisation for coronary artery, cerebrovascular, or peripheral artery disease at least 90 days after the delivery discharge date. FINDINGS The mean (SD) age of participants was 28.2 (5.5) years at the index delivery, and 75 380 (7%) women were diagnosed with a maternal placental syndrome. The incidence of cardiovascular disease was 500 per million person-years in women who had had a maternal placental syndrome compared with 200 per million in women who had not (adjusted hazard ratio [HR] 2.0, 95 CI 1.7-2.2). This risk was higher in the combined presence of a maternal placental syndrome and poor fetal growth (3.1, 2.2-4.5) or a maternal placental syndrome and intrauterine fetal death (4.4, 2.4-7.9), relative to neither. INTERPRETATION The risk of premature cardiovascular disease is higher after a maternal placental syndrome, especially in the presence of fetal compromise. Affected women should have their blood pressure and weight assessed about 6 months postpartum, and a healthy lifestyle should be emphasised.

Assessing the Minimal Important Difference in Symptoms: A Comparison of Two Techniques

We have developed a method for estimating the minimally important difference (MID) for health status measures. Whereas the conventional approach requires patients to judge themselves relative to their memories, our method requires patients to judge themselves relative to others with the same condition. In this study we examined whether our method (based on between-patient differences) and the conventional method (based on within-patient changes) provides comparable estimates of the MID for one health status measure: the Chronic Respiratory Questionnaire. Patients with chronic obstructive pulmonary disease who were participating in a supervised respiratory rehabilitation program were included if they were in stable health (n = 112). Their mean score per question in the Chronic Respiratory Questionnaire was 4.5 (range, 1 to 7; where bigger values indicate better health). Our method estimated that the MID was 0.5 (95% confidence interval 0.4 to 0.7). This estimate was similar to the MID previously found using the conventional method. These observations support the role of the Chronic Respiratory Questionnaire for measuring patients symptoms, the validity of our approach for assessing the MID, and an estimate on the order of 0.5 as the threshold for this particular health status measure.

Statins and sepsis in patients with cardiovascular disease: a population-based cohort analysis

BACKGROUND Atherosclerosis and sepsis share several pathophysiological similarities, including immune dysregulation, increased thrombogenesis, and systemic inflammation. The relation between statins and risk of sepsis in patients with atherosclerosis is unknown. METHODS We did a population-based cohort analysis through linked administrative databases in Ontario, Canada, with accrual from 1997 to 2002. We identified 141,487 patients older than 65 years who had been hospitalised for an acute coronary syndrome, ischaemic stroke, or revascularisation, who survived for at least 3 months after discharge. 46,662 (33%) were prescribed a statin within 90 days of discharge, 94,825 (67%) were not. Propensity-based matching, which accounted for each individuals likelihood of receiving a statin, yielded a cohort of 69,168 patients, of whom half (34,584) received a statin and half (34,584) did not. FINDINGS Incidence of sepsis was lower in patients receiving statins than in controls (71.2 vs 88.0 events per 10,000 person-years; hazard ratio [HR] 0.81; 95% CI 0.72-0.91). Adjustment for demographic characteristics, sepsis risk factors, comorbidities, and health-care use gave similar results (HR 0.81; 95% CI 0.72-0.90). The protective association between statins and sepsis persisted in high-risk subgroups, including patients with diabetes mellitus, chronic renal failure, or a history of infections. Significant reductions in severe sepsis (HR 0.83; 95% CI 0.70-0.97) and fatal sepsis (0.75; 0.61-0.93) were also observed. No benefit was noted with non-statin lipid-lowering agents (0.95; 0.75-1.22). IMPLICATIONS Use of statins in patients with atherosclerosis is associated with a reduced risk of subsequent sepsis. Randomised trials of statins for prevention of sepsis are warranted.

Angiotensin-converting enzyme inhibitors and aortic rupture: a population-based case-control study.

BACKGROUND Angiotensin-converting enzyme (ACE) inhibitors prevent the expansion and rupture of aortic aneurysms in animals. We investigated the association between ACE inhibitors and rupture in patients with abdominal aortic aneurysms. METHODS We did a population-based case-control study of linked administrative databases in Ontario, Canada. The sample included consecutive patients older than 65 (n=15,326) admitted to hospital with a primary diagnosis of ruptured or intact abdominal aortic aneurysm between April 1, 1992, and April 1, 2002. FINDINGS Patients who received ACE inhibitors before admission were significantly less likely to present with ruptured aneurysm (odds ratio [OR] 0.82, 95% CI 0.74-0.90) than those who did not receive ACE inhibitors. Adjustment for demographic characteristics, risk factors for rupture, comorbidities, contraindications to ACE inhibitors, measures of health-care use, and aneurysm screening yielded similar results (0.83, 0.73-0.95). Consistent findings were noted in subgroups at high risk of rupture, including patients older than 75 years and those with a history of hypertension. Conversely, such protective associations were not observed for beta blockers (1.02, 0.89-1.17), calcium channel blockers (1.01, 0.89-1.14), alpha blockers (1.15, 0.86-1.54), angiotensin receptor blockers (1.24, 0.71-2.18), or thiazide diuretics (0.91, 0.78-1.07). INTERPRETATION ACE inhibitors are associated with a reduced risk of ruptured abdominal aortic aneurysm, unlike other antihypertensive agents. Randomised trials of ACE inhibitors for prevention of aortic rupture might be warranted.

PRIMER ON MEDICAL DECISION ANALYSIS : PART 3-ESTIMATING PROBABILITIES AND UTILITIES

This paper describes how to estimate probabilities and outcome values for decision trees. Probabilities are usually derived from published studies, but occasionally are derived from existing databases, primary data collection, or expert judgment. Outcome values represent quantitative estimates of the desirability of the outcome states, and are often expressed as utility values between 0 and 1. Utility values for different health states can be derived from the published literature, from direct measurement in appropriate subjects, or from expert opinion. Methods for assigning utilities to complex outcome states are described, and the concept of quality-adjusted life years is introduced. Key words: decision analysis; expected value; utility; sensitivity analysis; decision trees; probability. (Med Decis Making 1997;17:136-141)

Primer on Medical Decision Analysis: Part 5—Working with Markov Processes

Clinical decisions often have long-term implications. Analysts encounter difficulties when employing conventional decision-analytic methods to model these scenarios. This occurs because probability and utility variables often change with time and conventional decision trees do not easily capture this dynamic quality. A Markov analysis performed with current computer software programs provides a flexible and convenient means of modeling long-term scenarios. However, novices should be aware of several potential pitfalls when attempting to use these programs. When deciding how to model a given clinical problem, the analyst must weigh the simplicity and clarity of a conventional tree against the fidelity of a Markov analysis. In direct comparisons, both approaches gave the same qualitative answers. Key words: decision analysis; expected value; utility; sensitivity analysis; decision trees; probability. (Med Decis Making 1997; 17:152-159)

Primer on Medical Decision Analysis: Part 1—Getting Started:

This paper is Part 1 of a five-part series covering practical issues in the performance of decision analysis. The intended audience is individuals who are learning how to perform decision analyses, not just read them. The series assumes familiarity with the basic concepts of decision analysis. It imparts many of the recommendations the authors have learned in teaching a one-semester course in decision analysis to graduate students. Part 1 introduces the topic and covers questions such as choosing an appropriate question, determining the tradeoff between accuracy and simplicity, and deciding on a time frame. Key words: decision analysis; expected value; utility; sensitivity analysis; decision trees; probability. (Med Decis Making 1997;17:123-125)