Increased Atrial Fibrillation Mortality: United States, 1980–1998

Wendy A. Wattigney, George A. Mensah and Janet B. Croft

From the Cardiovascular Health Branch, National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention, Atlanta, GA.


    ABSTRACT
 TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
The authors used death certificate data to evaluate national trends in the reporting of atrial fibrillation as an underlying or contributory cause of death for groups defined by age (45 years or older), sex, and race (Black vs. White) and to examine comorbidity. The multiple-causes mortality files from 1980 through 1998 were analyzed for decedents, with atrial fibrillation (International Classification of Diseases, Ninth Revision, code 427.3) listed as one of up to 20 conditions causing death. The number of decedents with atrial fibrillation increased from 18,947 in 1980 to 61,946 in 1998, and the proportion with atrial fibrillation reported as the underlying cause of death rose from 8.3% in 1980 to 11.6% in 1998. Age-standardized death rates from 1980 to 1998 were consistently highest among White men, followed (in descending order) by White women, Black men, and Black women. Overall, the age-standardized rate (per 100,000) increased from 27.6 in 1980 to 69.8 in 1998 (an average annual increase of 5.4%, p < 0.0001). Ischemic heart disease was the most frequent underlying cause of death among decedents with atrial fibrillation (26.8%). These findings emphasize the need for increased application of proven prevention and control measures to decrease associated cardiovascular morbidity and mortality.

atrial fibrillation; atrial flutter; cardiovascular diseases; death; heart diseases

Abbreviations: ICD-9, International Classification of Diseases, Ninth Revision


    INTRODUCTION
 TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Atrial fibrillation, the most common sustained heart rhythm disturbance in humans, affects an estimated 2.2 million adults in the United States alone (1Go, 2Go). It accounts for nearly one in three hospital discharges in which a cardiac arrhythmia is listed as the principal diagnosis (3Go). Epidemiologic cohort studies have shown that the prevalence of atrial fibrillation increases markedly with age in older adults, from less than 1 percent for those younger than age 60 years to roughly 10 percent for persons aged 80 or older (1Go, 2Go, 4Go, 5Go). In the Framingham Heart Study cohort, men had a higher prevalence than women regardless of age and examination year. Secular trends from 1968 to 1989 among Framingham subjects aged 65–84 years showed an increase in prevalence of atrial fibrillation from 3.2 to 9.1 percent in men and from 2.8 to 4.7 percent in women (4Go). In a recent study of health maintenance organization enrollees, the prevalence of diagnosed atrial fibrillation among persons aged 50 years or older was higher in Whites than in Blacks (2.2 vs. 1.5 percent, p < 0.001) (2Go). Atrial fibrillation is an important marker for the presence of other cardiovascular diseases and a powerful independent predictor of morbidity and mortality (6Go).

Atrial fibrillation is an independent risk factor for stroke, with the attributable risk increasing with age to about 25 percent for adults aged 80 years or older (7Go). A report from the Framingham Heart Study (8Go) identified risk factors for chronic or transient atrial fibrillation after 38 years of follow-up. These included male sex, age, congestive heart failure, valvular heart disease, a history of myocardial infarction, hypertension, and diabetes (8Go). In the Cardiovascular Health Study, left atrial size was also a strong independent predictor of incidence during 3 years of follow-up, a finding that suggests a cause for, not a consequence of, atrial fibrillation (9Go). Levels of blood pressure and glucose were also more important as predictors than was diagnosis of high blood pressure and diabetes (9Go).

Much of our knowledge of the prognosis and predisposing conditions for atrial fibrillation is provided by cohort studies and is based on predominantly White cohorts. National mortality patterns in population groups defined by race, sex, and age have not been reported. Multiple-cause mortality files for 1980–1998 provide an opportunity to evaluate not only national trends in reporting the presence of atrial fibrillation as a cause of death in the US population but also the frequency of coexisting conditions contributing to death.


    MATERIALS AND METHODS
 TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
The National Center for Health Statistics, Centers for Disease Control and Prevention, compiles data on all deaths occurring annually in the United States from vital records of states and the District of Columbia (10Go, 11Go). Public use data files contain the underlying cause, up to 19 additional contributing causes, and demographic data. At the state vital statistics office, information from death certificates is entered into electronic records. All of the diseases and conditions reported on death certificates from 1979 through 1998 used codes from the International Classification of Diseases, Ninth Revision (ICD-9) (12Go). The underlying cause of death is the disease (or injury) that initiated the sequence of events leading directly to death. Usually, the underlying cause of death is the condition reported on the lowest line in part I of the death certificate. In some cases, however, the interpretations of individual physicians are overruled on the basis of international selection and modification rules to select a condition of greater public interest or to correct for poor reporting practices (10Go). In this report, atrial fibrillation is defined for decedents with ICD-9 code 427.3 mentioned as either the underlying cause or as a contributory (any one of the possible 20 conditions on the death certificate) cause of death. This code includes both atrial fibrillation and atrial flutter.

We limited the National Center for Health Statistics multiple-cause mortality data to deaths occurring in the 50 states and the District of Columbia among US residents. We describe trends from 1980 through 1998 in the annual number and age-standardized rate of decedents aged 45 years or older with atrial fibrillation reported as one of up to 20 conditions on the death certificate, the age distribution, and the percentage of persons with atrial fibrillation reported as the underlying cause of death. Persons aged less than 45 years accounted for less than 0.2 percent of all decedents with atrial fibrillation.

Age-standardized death rates were estimated by race (Black and White) and sex for atrial fibrillation as a multiple cause using 2-year intervals from 1981 through 1998. All races other than Black or White combined contributed to approximately 1 percent of decedents with atrial fibrillation. Detailed race groups were too few to provide comparable results. Projections of the US resident population by age, sex, and race from the US Bureau of the Census were used to calculate age-, race-, and sex-specific death rates per 100,000 US population. Death rates were age standardized using the direct method for adjustment to the year 2000 standard population aged 45 years and older (13Go). Annual percentage changes in death rates were estimated with log-linear regression (14Go). Age-specific death rates for White and for Black adults were estimated with the use of 2-year intervals from 1981 through 1998.

For 1994–1998 aggregate data, the distribution of disease categories (ICD-9 codes 001.0–799.9, a range that excludes external causes of injury and poisoning) reported as the underlying cause of death was examined among decedents aged 45 or more years with atrial fibrillation by age (45–64 years and >=65 years) and by race and sex (White men, White women, Black men, and Black women). Comorbid causes on death certificates mentioning atrial fibrillation were likewise investigated. These analyses did not include decedents who had an external cause of injury or poisoning coded as the underlying cause of death (ICD-9 codes 800.0–999.9). External cause of injury and poisoning were reported as the underlying cause of death for 0.7 and 1.2 percent of decedents with atrial fibrillation aged 45–64 and 65 or more years, respectively.


    RESULTS
 TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
There was an increasing trend from 1980 through 1998 in multiple-cause death rates for atrial fibrillation among adults aged 45 or more years (table 1). The number of decedents with atrial fibrillation increased from 18,947 in 1980 to 61,946 in 1998. The age-standardized rate (per 100,000 US population) increased from 27.6 in 1980 to 69.8 in 1998 (an average annual increase of 5.4 percent, p < 0.0001). In the period 1980–1988, the average annual increase was 3.1 percent compared with 6.2 percent from 1989 to 1998. The proportion of all decedents with atrial fibrillation who were aged 85 or more years increased from 34 percent in 1980 to 47 percent in 1998. Of all decedents with atrial fibrillation, an increasing proportion of persons had atrial fibrillation reported as the underlying cause of death (from 8.3 percent in 1980 to 11.6 percent in 1998). From 1980 to 1998, the race and sex distribution of decedents with atrial fibrillation remained relatively constant, with almost 94 percent being White and almost 60 percent being women.


View this table:
[in this window]
[in a new window]
 
TABLE 1. Trends in death rates and selected characteristics among decedents aged 45 years or older with atrial fibrillation listed as one of up to 20 conditions on the death certificate, United States, 1980–1998

 
Age-standardized death rates varied between race and sex groups among adults aged 45 or more years (figure 1). For atrial fibrillation as the underlying cause of death, death rates were higher among White than among Black adults. After 1988, age-standardized death rates for atrial fibrillation as the underlying cause of death increased linearly with a greater increase seen among White decedents. A considerable White-Black gap is evident in more recent years. The age-standardized rate (per 100,000) increased from about 2.5 in 1981–1982 to approximately eight and five in 1997–1998 among White and Black adults, respectively. Similarly, there was a consistent increase from 1981 through 1998 in death rates for atrial fibrillation listed as any condition on the death certificate among adults aged 45 or more years. These age-standardized death rates were consistently highest among White men, followed (in descending order) by White women, Black men, and Black women. The average annual increase ranged from 1.2 percent in Black women to 1.6 percent in White men from 1980 to 1988 and accelerated to about 5.0 percent in Blacks and 6.5 percent in Whites from 1988 to 1998.



View larger version (22K):
[in this window]
[in a new window]
 
FIGURE 1. Age-standardized death rates for atrial fibrillation as the underlying cause of death or as one of up to 20 conditions listed on the death certificates of adults aged 45 years or older, by race, sex, and 2-year intervals, United States, 1981–1998. WM, White males; WF, White females; BM, Black males; BF, Black females.

 
Age-specific death rates (ages 65–74, 75–84, and >=85 years) by race and calendar year show a temporal increase for each age-race group, with Whites aged 75–84 and 85 or more years having much higher absolute death rates than did Blacks in the corresponding age categories for atrial fibrillation as either the underlying cause or any condition (figure 2). In 1997–1998, the death rate for Whites aged 85 or more years was twice that for Blacks—97 versus 47 (per 100,000). The relative increase over time in atrial fibrillation as the underlying cause of death was consistently greater among Whites than among Blacks and was most pronounced in those aged 85 or more years (294 percent in Whites and 140 percent in Blacks). Racial differences were not observed in the relative increase over time for atrial fibrillation as any condition at death. Death rates among adults aged 45–64 years were close to zero.



View larger version (26K):
[in this window]
[in a new window]
 
FIGURE 2. Age-specific death rates for atrial fibrillation as the underlying cause of death or as one of up to 20 conditions listed on the death certificate of adults aged 65 years or older, by race, age group, and 2-year intervals, United States, 1981–1998. The lines often overlap for decedents aged 65–74 years.

 
The distribution of disease categories that were coded as the underlying cause of death for 1994 through 1998 for all decedents with atrial fibrillation did not differ markedly by age (table 2). Specific disease categories and subcategories that were frequent by at least 5.0 percent within an age group are presented. Diseases of the circulatory system were the most common cause of death (62.3 percent among decedents aged 45–64 years and 68.6 percent among those aged >=65 years). Among these circulatory system diseases, ischemic heart disease was the most frequent underlying cause of death (23.4 percent for ages 45–64 years and 27.2 percent for ages >=65). Ischemic heart disease, atrial fibrillation and flutter, and cerebrovascular disease were slightly more common among decedents aged 65 or more years than among those aged 45–64 years. In the younger age cohort, neoplasms, diabetes, and cardiomyopathy were more frequent as the underlying cause of death.


View this table:
[in this window]
[in a new window]
 
TABLE 2. Disease categories* coded as the underlying cause of death among decedents aged 45 years or older with atrial fibrillation, by age group, United States, 1994–1998

 
The distribution of disease categories that were coded as the underlying cause of death for 1994–1998 for all decedents with atrial fibrillation also differed slightly by race and sex (table 3). Race groups other than White or Black were too few in number (3,129; 1.2 percent) to provide comparable results. Table 3 lists specific disease categories and subcategories that were frequent (at least 5 percent) within a race-sex group. Ischemic heart disease was the most frequent underlying cause of death among persons who had atrial fibrillation as one of up to 20 conditions listed on the death certificate. Deceased women had a higher prevalence of circulatory system diseases reported as the underlying cause of death than did men (71.2 vs. 64.0 percent), including atrial fibrillation (approximately 13 percent vs. approximately 10 percent), while men had a higher prevalence of neoplasms (12–13 vs. approximately 7 percent).


View this table:
[in this window]
[in a new window]
 
TABLE 3. Distribution of disease categories* coded as the underlying cause of death among decedents aged 45 years or older with atrial fibrillation, by race-sex group, United States, 1994–1998

 
The percentage of selected ICD-9 categories coded as one of up to 20 conditions on the death certificate among decedents with atrial fibrillation was examined by age group (45–64 vs. >=65 years) and by race/sex group for data aggregated from 1994 through 1998. More than 84 percent of decedents in each age group (data not shown) and race/sex group (table 4) had at least one disease of the circulatory system other than atrial fibrillation listed on their death certificate. Among these, hypertensive disease, ischemic heart disease, cardiac arrest, heart failure, and cerebrovascular disease were prominent in all groups. Hypertensive disease was notably more frequent in Blacks than in Whites (30 vs. 19 percent). Diseases of the respiratory system, particularly chronic obstructive pulmonary disease, accompanied atrial fibrillation in a greater percentage of men than women (35 vs. 25 percent). Endocrine, nutritional, and metabolic diseases and immunity disorders, particularly diabetes, were comorbidities for roughly 20 percent of decedents with atrial fibrillation. Diabetes was a coexisting condition at death for a greater percentage of persons aged 45–64 years than for those aged 65 or more years (19 vs. 12 percent, data not shown) and was slightly more prevalent among Black female decedents (16 vs. 11–13 percent).


View this table:
[in this window]
[in a new window]
 
TABLE 4. Distribution of disease categories* coded as one of the 20 conditions listed on the death certificate among decedents aged 45 years or older with atrial fibrillation, by race-sex group, United States, 1994–1998

 

    DISCUSSION
 TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Atrial fibrillation affects primarily persons aged 75 years or more. Age-standardized rates (per 100,000 US population) of decedents with atrial fibrillation have increased overall from 27.6 in 1980 to 69.8 in 1998. White men consistently had the highest age-standardized rate over time, followed (in descending order) by White women, Black men, and Black women. Age-specific rates by race showed that White decedents aged 85 or more years had twice the rate for atrial fibrillation as that associated with death than Blacks; in 1997–1998, the rates were 749 versus 363 per 100,000 population, respectively. The proportional mortality (number of deaths associated with atrial fibrillation divided by the total deaths) also increased over time and was greatest for White women, who tend to live longer (data not shown).

The observed increase in mortality associated with atrial fibrillation sharply contrasts with the decline in death rates since the midcentury from most heart diseases, such as coronary heart disease, hypertensive disease, and rheumatic disease (15Go). Prolonged survival with diseases associated with atrial fibrillation, such as coronary heart disease, ischemic heart disease, and hypertensive disease, may have resulted in more cases of atrial fibrillation. As the proportion of elderly adults in the US population increases, atrial fibrillation will continue to be a more frequent diagnosis. Another factor that contributes to the increase in mortality associated atrial fibrillation is the growing prevalence of diabetes mellitus among older persons (16Go). With the higher prevalence of atrial fibrillation and associated clinical cardiovascular diseases among older adults and the contemporary appreciation of the importance of anticoagulation therapy in preventing stroke, both incidence and recognition of atrial fibrillation have grown and will likely continue to increase over time.

Investigators for a Danish hospital-based study noted a decrease from 1980 to 1993 of 12–13 percent for total mortality in patients with atrial fibrillation; however, hospital discharges for atrial fibrillation increased over the same period (17Go). The number of hospitalizations related to atrial fibrillation in Scotland has also increased dramatically in recent years, from 5,446 in 1986 to 17,279 in 1996 (18Go). Interestingly, nearly half of the patients admitted to Danish hospitals with atrial fibrillation had ischemic heart disease; hypertension was seen in fewer than 20 percent. By contrast, population-based studies have suggested that hypertension was the most common underlying medical problem in patients with atrial fibrillation (8Go). The observed decrease in mortality for patients with atrial fibrillation suggests that hospital-based analyses may not represent a true reflection of mortality. There is some speculation that the risk of in-hospital death declined due to changes in admission and discharge practices with a tendency toward earlier discharges to nursing homes and convalescent facilities. Furthermore, contemporary data from large, population-based surveys of atrial fibrillation are needed to examine the impact of comorbid conditions on the treatment and management of atrial fibrillation.

The increase in reporting of atrial fibrillation as an underlying cause or a multiple cause on the death certificate was gradual from 1980 to 1988 and much greater thereafter. Notably, the US Standard Certificate of Death was revised in 1989 to improve the quality of mortality data. Added instructions about cause of death stated, "Do not enter the mode of dying, such as cardiac or respiratory arrest, shock, or heart failure." However, heart failure and cardiac arrest were listed as a coexisting conditions at death for approximately 30 and 16 percent, respectively, of decedents with atrial fibrillation. It is possible that the instruction about cardiac arrest and heart failure influenced reporting of atrial fibrillation as the underlying cause. The 1989 revised death certificate probably did not affect the increasing trend in deaths with atrial fibrillation listed as a contributory cause, however. Medicare data indicate a similar increasing trend between 1991 and 1998 in the prevalence of hospitalizations of patients with atrial fibrillation (19Go). The availability of more advanced diagnostic tools such as ultrasound and electrographic monitoring likely contribute to the increased diagnosis of atrial fibrillation.

Regardless of the underlying cause, approximately 87 percent of all decedents had at least one disease of the circulatory system other than atrial fibrillation listed on the death certificate. Ischemic heart disease was one of the leading comorbidities and was observed more often among White (37 percent) than among Black (30 percent) decedents. Cerebrovascular disease/stroke was a coexisting condition contributing to death in approximately 27 percent of male decedents and 34 percent of female decedents. Hypertensive disease as a comorbid condition was more frequent among Blacks than among Whites (30 vs. 19 percent, respectively). Diseases of the respiratory system and neoplasms were more common among male than among female decedents. These coexisting conditions contributing to death reflect the independent risk factors predisposing to the development of atrial fibrillation identified in population-based cohort studies (8Go, 9Go) and concomitant diagnoses observed in hospital-based studies (17Go, 18Go).

The quality and completeness of the mortality data from the vital statistics system is a major strength of this study. That data source is unmatched in terms of universal coverage and standardization. Information that the national vital statistics system provides is often used in state and national initiatives to influence and target the direction of public health efforts. The widespread use of these data, however, has raised questions regarding the reliability and validity of cause-of-death information from the death certificate (20Go, 21Go). There is some lack of precision in cause-of-death specifications by physicians and of biases in the data on the underlying cause of death due to the coding protocols used. A limitation of the multiple-cause mortality records is that there is no verification of the death certificate data. There is also a general lack of resources to conduct cause-of-death queries with the certifying physician to clarify illegible, imprecise, or nonspecific entries. The reliability and accuracy of underlying cause depends on the medical certifier of each death as well as on automated software and the state and national nosologists who determine the codes and underlying cause.

The observations presented indicate that death associated with atrial fibrillation has risen and will likely continue to rise. As the elderly population in the United States increases in size, the public health burden of atrial fibrillation will assume more importance. In a prospective cohort study of hospitalized Medicare patients, the net impact of atrial fibrillation on mortality, stroke, and medical costs was studied (22Go). Total Medicare spending was greater in patients with than in those without atrial fibrillation (9–23 percent greater in men and 10–11 percent greater in women). Treatment of hypertension and diabetes and prevention of other cardiovascular diseases associated with atrial fibrillation may help reduce its prevalence. Anticoagulants have been shown to reduce stroke by 68 percent in eligible patients with atrial fibrillation (23Go). Nevertheless, a recent study in the United Kingdom suggests that only 23 percent of atrial fibrillation patients use anticoagulants and that use was lowest among elderly women, who might benefit the most (24Go).

The frequency with which atrial fibrillation is reported on death certificates as a contributory cause of mortality has increased in the United States over the last 2 decades. This trend is likely to continue as the US population ages. Effective anticoagulation, heart rate control, and conversion of atrial fibrillation to normal sinus rhythm are expected to decrease cardiovascular complications. Prevention of atrial fibrillation in the first place, through the identification of modifiable risk factors and their effective treatment and control in those at risk for developing this condition, must be pursued and recognized as complementary management strategies for reducing cardiovascular morbidity and mortality.


    NOTES
 
Correspondence to Wendy A. Wattigney, Cardiovascular Health Branch, National Center for Chronic Disease Prevention and Health Promotion, Mailstop K-47, Centers for Disease Control and Prevention, 4770 Buford Hwy NE, Atlanta, GA 30341-3717 (e-mail: wdw0{at}cdc.gov).


    REFERENCES
 TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 

  1. Feinberg WM, Blackshear JL, Laupacis A, et al. Prevalence, age distribution, and gender of patients with atrial fibrillation. Arch Intern Med 1995;155:469–73.[Abstract]
  2. Go AS, Hylek EM, Phillips KA, et al. Prevalence of diagnosed atrial fibrillation in adults: national implications for rhythm management and stroke prevention: the Anticoagulation and Risk Factors in Atrial Fibrillation (ATRIA) Study. JAMA 2001;285:2370–5.[Abstract/Free Full Text]
  3. Dialy B, Lehman MH, Schumacher DN, et al. Hospitalization for arrhythmias in the United States: importance of atrial fibrillation. (Abstract). J Am Coll Cardiol 1992;19:41A.
  4. Kannel WB, Wolf PA, Benjamin EJ, et al. Prevalence, incidence, prognosis, and predisposing conditions for atrial fibrillation: population-based estimate. Am J Cardiol 1998;82:2N–9N.[ISI][Medline]
  5. Ryder KM, Benjamin EJ. Epidemiology and significance of atrial fibrillation. Am J Cardiol 1999;84:131R–8R.[ISI][Medline]
  6. Benjamin EJ, Wolf PA, D'Agostino RB, et al. Impact of atrial fibrillation on the risk of death: the Framingham Heart Study. Circulation 1998;98:946–52.[Abstract/Free Full Text]
  7. Wolf PA, Abbott RD, Kannel WB. Atrial fibrillation as an independent risk factor for stroke: the Framingham Study. Stroke 1991;22:983–8.[Abstract]
  8. Benjamin EJ, Levy D, Vaziri SM, et al. Independent risk factors for atrial fibrillation in a population-based cohort: the Framingham Heart Study. JAMA 1994;271:840–4.[Abstract]
  9. Psaty BM, Manolio TA, Kuller LH, et al. Incidence of and risk factors for atrial fibrillation in older adults. Circulation 1997;96:2455–61.[Abstract/Free Full Text]
  10. Murphy SL. Deaths: final data for 1998. National vital statistics reports. Vol 48, no. 11. Hyattsville, MD: National Center for Health Statistics, 2000.
  11. National Center for Health Statistics. Public use data file documentation: multiple cause of death for ICD-9, 1998 data. Hyattsville, MD: US Public Health Service, 2000.
  12. World Health Organization. International classification of diseases. Manual of the international statistical classification of diseases, injuries, and causes of death. Ninth Revision. Geneva, Switzerland: World Health Organization, 1977.
  13. Klein RJ, Schoenborn CA. Age adjustment using the 2000 projected U.S. population. Healthy People Statistical Notes, no. 20. Hyattsville, MD: National Center for Health Statistics, 2001.
  14. Kleinman JC. State trends in infant mortality, 1968–83. Am J Public Health 1986;76:681–7.[Abstract]
  15. Cooper R, Cutler J, Desvigne-Nickens P, et el. Trends and disparities in coronary heart disease, stroke, and other cardiovascular diseases in the United States. Findings of the National Conference on Cardiovascular Disease Prevention. Circulation 2000;102:3137–47.[Abstract/Free Full Text]
  16. Mokdad AH, Ford ES, Bowman BA, et al. Diabetes trends in the U.S.: 1990–1998. Diabetes Care 2000;23:1278–83.[Abstract]
  17. Frost L, Engholm G, Moller H, et al. Decrease in mortality in patients with a hospital diagnosis of atrial fibrillation in Denmark during the period 1980–1993. Eur Heart J 1999;20:1592–9.[Abstract/Free Full Text]
  18. Stewart S, MacIntyre K, MacLeod MM, et al. Trends in hospital activity, morbidity and case fatality related to atrial fibrillation in Scotland, 1986–1996. Eur Heart J 2001;22:693–701.[Abstract/Free Full Text]
  19. Baine WB, Yu W, Weis KA. Trends and outcomes in the hospitalization of older Americans for cardiac conduction disorders or arrhythmias, 1991–1998. J Am Geriatr Soc 2001;49:763–70.[ISI][Medline]
  20. Zemach R. What the vital statistics system can and cannot do. (Editorial). Am J Public Health 1984;74:756–8.[ISI][Medline]
  21. Rosenberg HM. Improving cause-of-death statistics. (Editorial). Am J Public Health 1989;79:563–4.[ISI][Medline]
  22. Wolf PA, Mitchell JB, Baker CS, et al. Impact of atrial fibrillation on mortality, stroke, and medical cost. Arch Intern Med 1998;158:229–34.[Abstract/Free Full Text]
  23. Risk factors for stroke and efficacy of antithrombotic therapy in atrial fibrillation: pooled data from five randomized controlled trials. Arch Intern Med 1994;154:1449–57.[Abstract]
  24. Sudlow M, Thomson R, Thwaites B, et al. Prevalence of atrial fibrillation and eligibility for anticoagulants in the community. Lancet 1998;352:1167–71.[ISI][Medline]
Received for publication June 25, 2001. Accepted for publication December 26, 2001.