Stroke Epidemiology. Dexter L. Morris, PhD, MD Emily B. Schroeder, MSPH

Transcription

1 Stroke Epidemiology Dexter L. Morris, PhD, MD Emily B. Schroeder, MSPH

2 Stroke Epidemiology Page 2 of 9 Stroke Epidemiology Introduction Stroke is the third leading cause of death in the United States (US) and a leading cause of serious, long-term disability. (American Heart Association). In the US, about 15% of strokes are hemorrhagic and 85% ischemic. (Rosamond; van Gijn) Of the nonhemorrhagic strokes, approximately 25% of strokes are due to small vessel disease (lacunar strokes), 25% are due to embolism from the heart (thromboembolic strokes), and the remainder large vessel disease. (van Gijn) Stroke Mortality Stroke mortality has been the main measure of stroke occurrence. In 1998 there were 158,448 deaths from stroke in the US. (American Heart Association) Age-adjusted stroke death rates have been declining in the US for several decades. For example, the ageadjusted death rate for white males has declined from approximately 100/100,000 in 1979 to 56/100,000 in 1998 (adjusted to the 2000 US population standard). This trend has been seen in all race-sex groups.(cdc Wonder) Stroke mortality varies considerably by race and sex. In general, males have slightly higher age-adjusted stroke rates than females. Blacks have a very high stroke mortality rate. For example, the age-adjusted mortality rate for black males in 1998 was 84/100,000 compared to 56/100,000 for whites (adjusted to the 2000 US population standard). (American Heart Association; CDC Wonder) Similar differences are seen between black and white females. (American Heart Association; CDC Wonder) While the mortality data comparing Hispanics to blacks and whites is unclear, recent data suggests that Hispanics have a stroke incidence rate that is between that of whites and blacks. (CDC; Sacco) Strokes occur at any age but are much more common in the elderly, with the death rate doubling every ten years between 55 and 85 (American Heart Association). Because of this and the age distribution of the population, approximately 3/4 of stroke deaths occur in individuals over 65. (Murphy; American Heart Association) There are geographic differences in stroke mortality. In the US, a belt of high mortality was identified many years ago that encompassed many of the southeastern states. (Pickle). While geographic patterns have changed somewhat in recent years, this pattern still exists. For example, in 1998 blacks in North Carolina had nearly three times the age adjusted mortality rate than blacks living in New York. (CDC Wonder) The causes for this distribution are not entirely clear but are likely related in part to the distribution of hypertension and other stroke risk factors. Stroke is a disease of developed nations. While stroke mortality is declining in the US, worldwide it is increasing along with modernization. In particular, rates in Eastern Europe have been increasing, such that currently the highest rates are found in countries such as Bulgaria, Romania, and Hungary. Portugal and Japan also have high stroke rates.

3 Stroke Epidemiology Page 3 of 9 (World Health Organization; Wolf - book) It is anticipated that by 2020, stroke will have moved from the 6 th leading cause of lost disability adjusted life years (DALY s) to 4 th. (Murray) While stroke mortality rates have declined, the number of total stroke deaths has increased in the US in the 1990s. This is because the rate of decline slowed and the number of elderly in the US increased dramatically. This trend may continue as the percentage of older individuals grows. The population distribution affects who dies of stroke. (American Heart Association) Despite the increased mortality rate among black males, over 50% of all stroke deaths in the US occur in white females. (Murphy) Stroke Incidence Unlike cancer, there is little information on the incidence of stroke in the US. Two recent registries have been formed in Cincinnati and Manhattan. (Sacco; Broderick) Using data from these studies it is estimated that there are over 750,000 first-ever or recurrent strokes cases of stroke in the US each year. (Broderick) Hopefully in the future, additional registries will give us a much better picture of stroke occurrence in the US. Natural History and Prevalence Strokes tend not to be immediately fatal. The thirty-day mortality rate for ischemic strokes is 7.6% compared to 37.5% of hemorrhagic strokes. (Rosamond) Of those individuals who survive the first 30 days, 20% require some sort of institutionalized care. (American Heart Association) While there are few sources of data, it is estimated the prevalence of stroke among Americans age 20 and older is 11/1,000 persons (Adams). The prevalence of stroke among Americans age 65 and older is 40/1,000 persons, and one in 10 Americans over 75 has experienced a stroke (Adams). There are about 4,500,000 stroke survivors alive today in the US (American Heart Association). Risk Factors Risk factors for stroke have been well studied. As mentioned above, age (older), race (black) and sex (male) are all strong risk factors. People with atrial fibrillation have a very high risk of stroke compared to the general population (RR of 1.8 for men and 3.2 for women) and hence the importance of anticoagulation in this group (Wolf). Those with carotid bruits, previous strokes, diabetes and heart disease are also at higher risk of stroke (Wolf). There are several risk factors for stroke that are modifiable. These include smoking and hypertension. Hypertension is by far the single major modifiable cause of stroke in the US (Wolf; Wolf - book). It has been estimated that stroke incidence could be cut in half if hypertension were appropriate treated (Wolf book). One in four adults has hypertension and at least 30% are unaware they have it let alone are treated for it (American Heart Association). Controlling hypertension is the single most effective way of reducing stroke mortality in the US. (Wolf-book) 1

4 Stroke Epidemiology Page 4 of 9 Healthcare Costs In 1997 over 1,000,000 patients were discharged from the hospital with a diagnosis of stroke (American Heart Association). A large percentage of these patients present through the emergency department. These discharges have increased 35% from 1979 to (American Heart Association) About 8% of ischemic stroke and 38% of hemorrhagic strokes die within 30 days. (Rosamond) Institutional care is required by 20-30% after discharge. At approximately $6,000 per hospitalization that is 6 billion dollars in hospitalization costs alone (American Heart Association). Total estimated costs of stroke in 2001 were estimated at over 45 billion dollars, of which over 17 billion dollars were due to lost productivity (American Heart Association). Because of the large health care costs of stroke, even treatments such as tpa which are expensive and do not work in all individuals, can significantly lower overall healthcare costs for stroke. (Fagan).

5 Stroke Epidemiology Page 5 of 9 Stroke Epidemiology Summary Stroke is a major cause of morbidity and mortality in the United States and although stroke rates are declining, the number of strokes is increasing because of the growth and aging of the population. Emergency department physicians will be faced with an increasing number of strokes and need to play a key role in the treatment and prevention of this disease.

6 Stroke Epidemiology Page 6 of 9 Stroke Epidemiology Bibliography 1. Adams PF, Hendershot GE, and Marano MA. Current estimates from the National Health Interview Survey, National Center for Health Statistics. Vital Health Statistics 10(200) Good source of prevalence and risk factor data. Available online at 2. American Heart Association Heart and Stroke Statistical Update. Dallas, Texas: American Heart Association, Excellent source of up to date facts and figures. Also see the web site americanheart.org and look in the professional statistics section. 3. Broderick J, Brott T, Kothari R, Miller R, Khoury J, Pancioli A, Gebel J, Mills D, Minneci L, Shukla R. The Greater Cincinnati / Northern Kentucky Stroke Study. Stroke 1998;29: From one of the few existing stroke registries in the U.S. 4. CDC Wonder program. A great source of data from CDC, including age-adjusted mortality rates for various diseases. 5. Age-specific excess deaths associated with stroke among racial/ethnic minority populations United States, MMWR 2000;49: A comparison of stroke mortality rates for different racial/ethnic groups. 6. Fagan SC, Morgenstern LB, Petitta A, Ward RE, Tilley BC, Marler JR, Levine SR, Broderick JP, Kwiatkowski TG, Franekl M, Brott TG, Walker MD. Cost-effectiveness of tissue plasminogen activator for acute ischemic stroke. Neurology 1998; 50: Article on the cost-effectiveness of rt-pa using data from the NINDS rt-pa trial. 7. Murphy SL. Deaths: Final Data for National vital statistics reports; vol 48 no 11. Hyattsville, Maryland: National Center for Health Statistics Compilation of vital statistics from the CDC. Available online at /

7 Stroke Epidemiology Page 7 of Murray JL, Lopez AD, ed.. The global burden of disease: a comprehensive assessment of mortality and disability from diseases, injuries, and risk factors in 1990 and projected to 2020, Cambridge, Mass: Harvard University Press, A frequently referenced ranking of the global burden of various diseases. 9. Pickle LW, Mungiole M, Gillum RF. Geographic variation in stroke mortality in Blacks and Whites in the United States. Stroke 1997;28: Includes detailed maps of the geographic distribution of stroke mortality rates. 10. Rosamond WD, Folson AR, Chambless LE, Wang C-H, McGovern PG, Howard G, Copper LS, Shahar E. Stroke incidence and survival among middle-aged adults: 9-year follow-up of the Atherosclerosis Risk in Communities (ARIC) Cohort. Stroke 1999;30: Article from the surveillance component of the Atherosclerosis Risk in Communities epidemiological study. Includes incidence, mortality and casefatality data. 11. Sacco RL, Bodan-Albala B, Gan R, Chen X, Kargman DE, Shea S, Paik MC, Hauser WA. Stroke incidence among White, Black, and Hispanic residents of an urban community: the Northern Manhattan Stroke Study. American Journal of Epidemiology 1998;147: From one of the few existing stroke registries in the U.S. 12. Van Gijn J. Main groups of cerebral and spinal vascular disease: overview. In Ginsberg MD, Bogousslavsky J, eds. Cerebrovascular disease: pathophysiology, diagnosis, and management. Malden, Mass: Blackwell Science, Brief overview. 13. Wolf PA, D Agostino RB, Belanger AJ, Kannel WB. Probability of Stroke: A risk profile from the Framingham Study. Stroke 1991;22: The classic Framingham risk equation for stroke. 14. Wolf PA, Kannel WB, D Agostino RB. Epidemiology of stroke. In Ginsberg MD, Bogousslavsky J, eds. Cerebrovascular disease: pathophysiology, diagnosis, and management. Malden, Mass: Blackwell Science, A comprehensive review.

8 Stroke Epidemiology Page 8 of World Health Organization. World Health Statistics Annual Selected Issues (Geneva: ) and WHO website: Good source of global figures for stroke and other diseases.

9 Stroke Epidemiology Page 9 of 10 Stroke Epidemiology Questions 1. What is the most important preventable cause of strokes? a. atrial fibrillation b. smoking c. hypertension d. hyperlipidemia 2. In the United States the group with the highest age-adjusted stroke mortality rate is? a. White men b. White females c. Black males d. Black females 3. In the United States, there are estimated to be new or recurrent strokes each year. a. 750,000 b. 500,000 c. 250,000 d. 100, Which of the following groups has the highest number of actual stroke deaths in the US each year: a. White men b. White women c. Black men d. Black women 5. Approximately what percentage of strokes are ischemic? a. 30% b. 15% c. 50% d. 85%

10 Stroke Epidemiology Page 10 of 10 Stroke Epidemiology Answers 1. Answer c, Hypertension. While there are many risk factors for stroke, hypertension is extremely prevalent and preventable. 2. Answer c, Black Males. Black males have almost twice the mortality rates as white males. Some of this is likely due to the prevalence of hypertension. 3. Answer a, 750,000. Using data from the new stroke registries the number of strokes occurring each year is estimated to be 750,000. In reality it is likely higher. 4. Answer b, White women. While rates are higher in black males, there are many more older white women who contribute to stroke mortality. 5. Answer d, 85%. Ischemic strokes make up 85% of strokes and hemorrhagic strokes make up 15%.