Joe V. Selby

CONTEXT: Atrial fibrillation is the most common arrhythmia in elderly persons and a potent risk factor for stroke. However, recent prevalence and projected future numbers of persons with atrial fibrillation are not well described. OBJECTIVE: To estimate prevalence of atrial fibrillation and US national projections of the numbers of persons with atrial fibrillation through the year 2050. DESIGN, SETTING, AND PATIENTS: Cross-sectional study of adults aged 20 years or older who were enrolled in a large health maintenance organization in California and who had atrial fibrillation diagnosed between July 1, 1996, and December 31, 1997. MAIN OUTCOME MEASURES: Prevalence of atrial fibrillation in the study population of 1.89 million; projected number of persons in the United States with atrial fibrillation between 1995-2050. RESULTS: A total of 17 974 adults with diagnosed atrial fibrillation were identified during the study period; 45% were aged 75 years or older. The prevalence of atrial fibrillation was 0.95% (95% confidence interval, 0.94%-0.96%). Atrial fibrillation was more common in men than in women (1.1% vs 0.8%; P<.001). Prevalence increased from 0.1% among adults younger than 55 years to 9.0% in persons aged 80 years or older. Among persons aged 50 years or older, prevalence of atrial fibrillation was higher in whites than in blacks (2.2% vs 1.5%; P<.001). We estimate approximately 2.3 million US adults currently have atrial fibrillation. We project that this will increase to more than 5.6 million (lower bound, 5.0; upper bound, 6.3) by the year 2050, with more than 50% of affected individuals aged 80 years or older. CONCLUSIONS: Our study confirms that atrial fibrillation is common among older adults and provides a contemporary basis for estimates of prevalence in the United States. The number of patients with atrial fibrillation is likely to increase 2.5-fold during the next 50 years, reflecting the growing proportion of elderly individuals. Coordinated efforts are needed to face the increasing challenge of optimal stroke prevention and rhythm management in patients with atrial fibrillation.

BACKGROUND: The efficacy of sigmoidoscopic screening in reducing mortality from colorectal cancer remains uncertain. A randomized trial would be ideal for clarifying this issue but is very difficult to conduct. Case-control studies provide an alternative method of estimating the efficacy of screening sigmoidoscopy. METHODS: Using data on the 261 members of the Kaiser Permanente Medical Care Program who died of cancer of the rectum or distal colon from 1971 to 1988, we examined the use of screening by rigid sigmoidoscopy during the 10 years before the diagnosis and compared it with the use of screening in 868 control subjects matched with the case subjects for age and sex. RESULTS: Only 8.8 percent of the case subjects had undergone screening by sigmoidoscopy, as compared with 24.2 percent of the controls (matched odds ratio, 0.30; 95 percent confidence interval, 0.19 to 0.48). Adjustment for potential confounding factors increased the odds ratio to 0.41 (95 percent confidence interval, 0.25 to 0.69). The negative association was as strong when the most recent sigmoidoscopy was 9 to 10 years before diagnosis as it was when examinations were more recent. By contrast, for 268 subjects with fatal colon cancer above the reach of the sigmoidoscope and for 268 controls, the adjusted odds ratio was 0.96 (95 percent confidence interval, 0.61 to 1.50). The specificity of the negative association for cancer within the reach of the sigmoidoscope is consistent with a true efficacy of screening rather than a confounding by unmeasured selection factors. CONCLUSIONS: Screening by sigmoidoscopy can reduce mortality from cancer of the rectum and distal colon. A screening once every 10 years may be nearly as efficacious as more frequent screening.

BACKGROUND: The incidence of stroke in patients with atrial fibrillation is greatly reduced by oral anticoagulation, with the full effect seen at international normalized ratio (INR) values of 2.0 or greater. The effect of the intensity of oral anticoagulation on the severity of atrial fibrillation-related stroke is not known but is central to the choice of the target INR. METHODS: We studied incident ischemic strokes in a cohort of 13,559 patients with nonvalvular atrial fibrillation. Strokes were identified through hospitalization data bases and validated on the basis of medical records, which also provided information on the use of warfarin or aspirin, the INR at admission, and coexisting illnesses. The severity of stroke was graded according to a modified Rankin scale. Thirty-day mortality was ascertained from hospitalization and mortality files. RESULTS: Of 596 ischemic strokes, 32 percent occurred during warfarin therapy, 27 percent during aspirin therapy, and 42 percent during neither type of therapy. Among patients who were taking warfarin, an INR of less than 2.0 at admission, as compared with an INR of 2.0 or greater, independently increased the odds of a severe stroke in a proportional-odds logistic-regression model (odds ratio, 1.9; 95 percent confidence interval, 1.1 to 3.4) across three severity categories and the risk of death within 30 days (hazard ratio, 3.4; 95 percent confidence interval, 1.1 to 10.1). An INR of 1.5 to 1.9 at admission was associated with a mortality rate similar to that for an INR of less than 1.5 (18 percent and 15 percent, respectively). The 30-day mortality rate among patients who were taking aspirin at the time of the stroke was similar to that among patients who were taking warfarin and who had an INR of less than 2.0. CONCLUSIONS: Among patients with nonvalvular atrial fibrillation, anticoagulation that results in an INR of 2.0 or greater reduces not only the frequency of ischemic stroke but also its severity and the risk of death from stroke. Our findings provide further evidence against the use of lower INR target levels in patients with atrial fibrillation.

OBJECTIVE: To evaluate if midlife cardiovascular risk factors are associated with risk of late-life dementia in a large, diverse cohort. METHOD: The authors conducted a retrospective cohort study of 8,845 participants of a health maintenance organization who underwent health evaluations from 1964 to 1973 when they were between the ages of 40 and 44. Midlife cardiovascular risk factors included total cholesterol, diabetes, hypertension, and smoking. Diagnoses of dementia were ascertained by medical records from January 1994 to April 2003. RESULTS: The authors identified 721 participants (8.2%) with dementia. Smoking, hypertension, high cholesterol, and diabetes at midlife were each associated with a 20 to 40% increase in risk of dementia (fully adjusted Cox proportional hazards model: HR 1.24, 95% CI 1.04 to 1.48 for hypertension, HR 1.26, 95% CI 1.08 to 1.47 for smoking, HR 1.42, 95% CI 1.22 to 1.66 for high cholesterol, and HR 1.46, 95% CI 1.19 to 1.79 for diabetes). A composite cardiovascular risk score was created using all four risk factors and was associated with dementia in a dose-dependent fashion. Compared with participants having no risk factors, the risk for dementia increased from 1.27 for having one risk factor to 2.37 for having all four risk factors (fully adjusted model: HR 2.37, 95% CI 1.10 to 5.10). CONCLUSION: The presence of multiple cardiovascular risk factors at midlife substantially increases risk of late-life dementia in a dose dependent manner.

BACKGROUND: Despite a recent American Heart Association (AHA) consensus statement emphasizing the importance of resistant hypertension, the incidence and prognosis of this condition are largely unknown. METHODS AND RESULTS: This retrospective cohort study in 2 integrated health plans included patients with incident hypertension in whom treatment was begun between 2002 and 2006. Patients were followed up for the development of resistant hypertension based on AHA criteria of uncontrolled blood pressure despite use of ≥3 antihypertensive medications, with data collected on prescription filling information and blood pressure measurement. We determined incident cardiovascular events (death or incident myocardial infarction, heart failure, stroke, or chronic kidney disease) in patients with and without resistant hypertension with adjustment for patient and clinical characteristics. Among 205 750 patients with incident hypertension, 1.9% developed resistant hypertension within a median of 1.5 years from initial treatment (0.7 cases per 100 person-years of follow-up). These patients were more often men, were older, and had higher rates of diabetes mellitus than nonresistant patients. Over 3.8 years of median follow-up, cardiovascular event rates were significantly higher in those with resistant hypertension (unadjusted 18.0% versus 13.5%, P<0.001). After adjustment for patient and clinical characteristics, resistant hypertension was associated with a higher risk of cardiovascular events (hazard ratio, 1.47; 95% confidence interval, 1.33-1.62). CONCLUSIONS: Among patients with incident hypertension in whom treatment was begun, 1 in 50 patients developed resistant hypertension. Patients with resistant hypertension had an increased risk of cardiovascular events, which supports the need for greater efforts toward improving hypertension outcomes in this population.