Robert B. Tate

The natural history of atrial fibrillation: Incidence, risk factors, and prognosis in the manitoba follow-up study

PURPOSE Atrial fibrillation is a common arrhythmia associated with increased cardiovascular morbidity and mortality. This study was undertaken to identify the natural history of this condition, including risk factors for its development, and outcome. PATIENTS AND METHODS The incidence of atrial fibrillation among 3,983 male air crew recruits observed continuously for 44 years was calculated based on person-years of observation. Age and 23 variables were examined to identify risk factors for atrial fibrillation. Controlling for age and 9 prognostic variables, the effect of atrial fibrillation on 8 outcomes was examined. Analysis of risk factors for atrial fibrillation and outcome after atrial fibrillation was based on a Cox proportional hazard model using time-dependent covariates. RESULTS Of the 3,983 study members, 299 (7.5%) developed atrial fibrillation during 154,131 person-years of observation. The incidence rose with age from less than 0.5 per 1,000 person-years before age 50 to 9.7 per 1,000 person-years after age 70. Risk for atrial fibrillation was increased with myocardial infarction (relative risk [RR] 3.62), angina (RR 2.84), and ST-T wave abnormalities in the absence of ischemic heart disease (RR 2.21). The RR for atrial fibrillation was strongest at the onset of ischemic heart disease and diminished over time. The rate of atrial fibrillation was 1.42 times increased in men with a history of hypertension. Congestive heart failure, valvular heart disease, and cardiomyopathy were important but uncommon risk factors. Atrial fibrillation independently increased the risk for stroke (RR 2.07) and congestive heart failure (RR 2.98). Total mortality rate was increased 1.31 times; cardiovascular mortality including and excluding fatal stroke were also increased (RR 1.41 and 1.37, respectively). CONCLUSIONS The incidence of atrial fibrillation in men increases with advancing age. Clinical cardiac abnormalities, particularly recent ischemic heart disease and hypertension, are strongly associated with increased risk for atrial fibrillation. Atrial fibrillation increases morbidity and mortality, but the magnitude of the increase may be less than previously reported.

The Manitoba Project: a re-examination of the link between menopause and depression

This paper re-examines the association between menopause and depression using data from a study in which 477 women were interviewed 6 times over a 3-year period. Menopause is examined as one of a series of factors which may increase the risk of depression for women in middle age, such as children leaving home, the death and illness of family members, the stresses of daily living, health and the onset of chronic disease. Rather than hormonal changes, it seems to be her health coupled with the shifts and stresses of family life in a womans menopausal years which may trigger her depression.

A randomized controlled trial to prevent patient lift and transfer injuries of health care workers.

Study Design. Randomized controlled trial (RCT). Objectives. To compare the effectiveness of training and equipment to reduce musculoskeletal injuries, increase comfort, and reduce physical demands on staff performing patient lifts and transfers at a large acute care hospital. Summary of Background Data. Back injury to nursing staff during patient handling tasks is a major issue in health care. The value of mechanical assistive devices in reducing injuries to these workers is unclear. Methods. This three-armed RCT consisted of a “control arm,” a “safe lifting” arm, and a “no strenuous lifting” arm. A medical, surgical, and rehabilitation ward were each randomly assigned to each arm. Both intervention arms received intensive training in back care, patient assessment, and handling techniques. Hence, the “safe lifting” arm used improved patient handling techniques using manual equipment, whereas the “no strenuous lifting” arm aimed to eliminate manual patient handling through use of additional mechanical and other assistive equipment. Results. Frequency of manual patient handling tasks was significantly decreased on the “no strenuous lifting” arm. Self-perceived work fatigue, back and shoulder pain, safety, and frequency and intensity of physical discomfort associated with patient handling tasks were improved on both intervention arms, but staff on the mechanical equipment arm showed greater improvements. Musculoskeletal injury rates were not significantly altered. Conclusions. The “no strenuous lifting” program, which combined training with assured availability of mechanical and other assistive patient handling equipment, most effectively improved comfort with patient handling, decreased staff fatigue, and decreased physical demands. The fact that injury rates were not statistically significantly reduced may reflect the less sensitive nature of this indicator compared with the subjective indicators.

Biomechanical analysis of peak and cumulative spinal loads during simulated patient-handling activities: a substudy of a randomized controlled trial to prevent lift and transfer injury of health care workers

Back injuries are a serious problem for nursing personnel who perform frequent patient-handling activities. Common prevention strategies include body mechanics education, technique training, and ergonomic interventions such as the introduction of assistive equipment. This investigation assessed and compared the effectiveness of two patient-handling approaches to reducing injury risk. One strategy involved using improved patient-handling technique with existing equipment, and the other approach aimed at eliminating manual patient handling through the use of additional mechanical and other assistive equipment. Both intervention arms received training in back care, patient assessment, and use of the equipment available on their particular wards. An analysis of compliance with interventions and the effects of patient-handling methods on both peak and cumulative spinal compression and shear during various tasks was conducted. Results showed greater compliance with interventions that incorporated new assistive patient-handling equipment, as opposed to those consisting of education and technique training alone. In several tasks, subjects who were untrained or non-compliant with interventions experienced significantly higher peak spinal loading. However, patient-handling tasks conducted with the aid of assistive equipment took substantially longer than those performed manually. This, along with variations in techniques, led to increases in cumulative spinal loading with the use of patient-handling equipment on some tasks. Thus, the use of mechanical assistive devices may not always be the best approach to reducing back injuries in all situations. No single intervention can be recommended; instead all patient-handling tasks should be examined separately to determine which methods maximize reductions in both peak and cumulative lumbar forces during a manoeuver.

The Natural History of Primary First-Degree Atrioventricular Heart Block

The long-term prognosis of first-degree heart block in the absence of organic heart disease has not been clearly defined. We addressed this question in a 30-year longitudinal study of 3983 healthy men. We identified 52 cases that were present on entry into the study and 124 incident cases during follow-up. The incidence rose steadily after age 40 and was 1.13 per 1000 person-years over the entire period. Two thirds of the cases had only moderate prolongation of the PR interval (0.22 to 0.23 second). We compared four age-matched controls with each case for histories of scarlet fever, rheumatic fever, diphtheria, smoking, blood pressure, and body-mass index. No significant differences (P greater than 0.05) were found. Likewise, mortality from all causes did not differ between cases and controls. Although somewhat higher rates of morbidity and mortality from ischemic heart disease were observed in the cases than in the controls, the differences were not significant. Progression to higher grades of heart block occurred in only two cases. In view of the prognostic findings and the rare occurrence of advanced degrees of heart block, we conclude that primary first-degree heart block with moderate PR prolongation is a benign condition. This conclusion may not apply, however, to persons with more marked prolongation of the PR interval, a very rare condition.

Predicting Risk of Ischemic Heart Disease and Cerebrovascular Disease from Systolic and Diastolic Blood Pressures

The relative importance of systolic versus diastolic blood pressure in predicting risk of ischemic heart disease or cerebrovascular disease is controversial. Since 1948 we have observed in the Manitoba Study 3983 men (most between 25 to 34 years old at entry), in whom risk of both diseases was determined using the multiple logistic model. Systolic and diastolic blood pressures after adjustment for age and body weight were compared at entry and at four other examinations during the follow-up period. When both blood pressures were considered together, a stronger association with cerebrovascular disease was found for systolic compared to diastolic blood pressure at entry and at most of the other examinations. For ischemic heart disease, diastolic pressure showed a stronger association at the earlier examinations, whereas systolic pressure was more important when the majority of the cohort was between 40 to 50 years of age. In middle-aged men the general concept that diastolic is more important than systolic is not justified for cerebrovascular disease or for ischemic heart disease.

Defining menopausal status: The impact of longitudinal data

A population of 324 women who were over 45 and still menstruating were followed for a period of 3 yr. They were interviewed 6 times at 6-mth intervals. This paper presents data on the changes in menstrual status that occurred over the period of the study and relating these changes in menstruation to a womans age and symptom experience.

The Natural History of Electrocardiographic Preexcitation in Men: The Manitoba Follow-up Study

OBJECTIVE To examine the natural history of preexcitation occurring on the routine electrocardiogram (ECG). DESIGN A longitudinal cohort study of 3983 originally healthy men followed prospectively for 40 years. SETTING Free-living (community-dwelling) study members residing predominantly in Canada. PARTICIPANTS Nineteen male study members with preexcitation occurring during routine examination in the 40-year follow-up of the Manitoba Follow-up Study. MEASUREMENTS Routinely requested clinical examinations and ECGs, supplemented by information supplied by the study member or his physician. MAIN RESULTS Ten study members were found to have preexcitation at enrollment, for a prevalence of 2.5 per 1000 (95% CI, 1.2 to 4.6). A delta wave was first detected during follow-up in an additional nine study members. Seventeen of 19 study members did not have the delta wave at some later time, and preexcitation was intermittently present in most of these members. Over time there was a loss of preexcitation, with 15 of 19 study members no longer exhibiting a delta wave by the end of follow-up. Five of 11 study members with symptoms had physician confirmation of an arrhythmia. Fourteen study members remain alive, and none of the five deaths was attributed to preexcitation. CONCLUSIONS Preexcitation found on routine ECG in our originally healthy male study group did not confer excess morbidity or mortality, even in those study members who developed symptomatic arrhythmias. Most preexcitation was intermittent and disappeared over time.

Does a Small Minority of Elderly Account for a Majority of Health Care Expenditures?: A Sixteen-Year Perspective

Canadian and American analysts commonly find that a small proportion of the elderly is responsible for a large share of health care expenditures. Data on a representative cohort in Manitoba indicate that the longer the time frame studied, the less health care usage concentrates in a single small group of elderly people. Over the sixteen-year period treated, the average older persons risks of using hospital and nursing home services is nevertheless notably higher than reported to date; yet, one-half of the elderly make relatively minimal demands on the health care system. The results reinforce calls for targeting the needs of intensive consumers of health care services and highlight the variability of cumulative usage patterns among older Manitobans.

Predictors of Long Term Care Facility Use among the Elderly

This research uses data from the Manitoba Longitudinal Study on Aging and multiple logistic regression analysis to assess the impact of twenty-eight sociodemographic and health status variables on nursing home admission. The results indicate that 1) all the short-term predictors continue to be significantly associated with facility bed use in the long run, suggesting that the high risk elderly can be identified relatively early; 2) the key sociodemographic characteristics are better predictors of admission than health and physical functioning characteristics; and 3) time itself appears to change the relationship of the study variables to admission.