Stroke Epidemiology

From Stroke Education
Jump to: navigation, search

Learning objectives

  • Incidence and prevalence of stroke
  • Impact of stroke - living with disability, cost
  • Changes in stroke epidemiology
  • Future predictions

Introduction

Epidemiology is useful as it helps to show the number of new strokes per year (incidence)and the numbers of those living who have had a stroke (prevalence). We can also see the effects of stroke regarding mortality. The distribution of stroke in a population can also help us to highlight potential causes and relationships. Finally, it helps us to plan and invest in and deliver appropriate hospital and community services. The worldwide experience with stroke depends on whether one is discussing a high versus low income country and where the ongoing care and financial burden lies - i.e. with family or with access to state support or elements of both. This variability can exists at different stratas within a country. Despite the sobering statistics on stroke, there has been a steady reduction in stroke mortality since the 1950's across the world.

Definitions

  • Incidence: Number of new cases of stroke reported in a specific time frame
  • Prevalence: Number of all those who currently or previously had a stroke.
  • Mortality: Deaths over a specific time frame in a population
  • Disability associated life years (DALY): Years of life lost to premature death + years lived with disability

Impact

In terms of Worldwide impact Stroke is the second most common cause of death. Stroke is the third biggest killer in England and the main cause of adult neurological disability - Stroke killed more than 40,000 people in 2009 in England and over 12,000 in NHS Midlands and East. Stroke is common, dangerous and expensive and for many is either lethal or disabling. It has huge physical, psychological and financial impact on patients and their carers and families and on society. As many patients do not seek help and have little contact with stroke services there may well be a large unsupported need in those with stroke living in the community. It is the third biggest killer after heart disease and cancer in England. It is the main cause of adult disability. Stroke killed more than 40,000 people in 2009 in England and over 12,000 in NHS Midlands and East.

Around two-thirds of people will survive their stroke, but half of stroke survivors are left with long-term disability and dependent on others for everyday activities. There are an estimated 900 000 stroke survivors in England, half of whom are dependent on others for care at an estimated cost of 2.4 billion. Stroke patients occupy around 20 percent of all acute hospital beds and 25 percent of long-term beds. Stroke units save lives: for stroke patients, general wards have a 14% to 25% higher mortality rate than stroke units. In a study across all of Europe total stroke incidence ranged in men ranged from 101.2 to 239.3 per 100000 (95% CI,82.5 to 123.0). The risk of stroke among European populations in our study varied more than 2-fold in men and women. On average, higher rates of stroke were observed in eastern and lower rates in southern European countries. The annual incidence of TIA is around 0.05% of the population of the UK. The good news is that stroke incidence rates fell 19% from 1990 to 2010 in the UK. The average age of stroke-affected patients has decreased in recent years.

Data Difficulties

  • Differentiating first ever stroke vs recurrent stroke: access to medical notes
  • Accurate medical knowledge of stroke, its type and aetiology
  • Those in the community with stroke unknown to healthcare services: using multiple information sources e.g. primary and secondary care and death certificates
  • Recording level of disability which may be changing: stroke team assessments

Facts and Figures

For every 100,000 people in a year in the UK there are
164 First Strokes + 57 Recurrent Strokes
10 Subarachnoid haemorrhages
44 Male stroke Deaths
33 Female Stroke Deaths
Prevalence 1,500 existing stroke cases
Prevalence 1,000 with moderate disability following stroke

Prevalence - The Stroke Burden

  • For every 100,000 people in the UK there are 1,500 existing stroke cases and 1,000 with moderate disability following stroke.
  • There is a wide variation worldwide and even within countries of stroke numbers. Stroke is probably under-reported.

Racial/Ethnic

  • Black and Asian patients are more likely to have strokes and to have them at a younger age group than whites. They have a greater incidence of hypertension and diabetes.
  • Maori and Pacific people have higher incidence of stroke
  • Sickle cell is commoner in Black patients.
  • White patients are more likely to have AF, smoke and take alcohol.

Gender

  • Females have a higher lifetime incidence (1 in 5) rather than men (1 in 6)
  • This is largely due to the fact that females live longer.
  • Women less likely to have a partner.
  • Women more likely to become institutionalised.

Socioeconomic

  • Those from lower income groups are more likely to have strokes and more severe strokes compared with those from higher income groups

Stroke Belt

  • You may come across this term and it reflects a geographical spread of poor stroke mortality across a number of US states. It involves 11 US states and although there are many theories the exact cause has not been fully explained.
  • The increased stroke risk is seen in both whites and blacks. There is a similar diabetes belt which covers the same area.
  • Although many possible causes for the high stroke incidence have been investigated, the reasons for the phenomenon have not been fully determined.

<img src="stroke_all.jpg" width=400>

Death - Stroke mortality

In the UK in 2000 there were 835 deaths per 100,000 (males) and of these 44 deaths per 100,000 attributable to stroke. Out of 559 deaths per 100,000 (females) there were 33 deaths per 100,000 attributable to stroke. The incidence of stroke has decreased in recent decades largely because of improved treatment of hypertension. Stroke mortality varies mainly due to the severity of stroke (NIHSS and Oxford scales are useful) and comorbidities rather than care. This is often missed in simplistic assessments of mortality between trusts. All comparisons of stroke outcomes should at least show that the baseline stroke characteristics are similar. Mortality also varies due to geographical areas, sex and races e.g. Stroke Mortality Rates in the USA. There is a wide variation worldwide and even within countries of stroke numbers. Stroke is probably under-reported. The average death rate is 20-25%. In other parts of the world healthcare systems differ and modes of accessing care vary so this can affect the statistics.

Stroke Mortality

  • 54/100,000 for white males
  • 53/100,000 for white females
  • 82/100,000 for black males
  • 72/100,000 for black females
  • 40/100,000 for Hispanics, American Indians and Alaskans
  • 52/100,000 for Asian/Pacific islanders

Future Predictions

Despite the sobering statistics on stroke, there has been a steady reduction in stroke mortality since the 1950's across the world. The improvements are unlikely to be due to modern advances in stroke management but possible due to less severe strokes. All epidemiological data is only as robust in the methods for collection and diagnosis of stroke. Issues are whether studies cover both hospital and/or community. Diagnostic methods - clinical or imaging and historical diagnosis. Certainly, imaging and publicity over stroke is perhaps increasing pickup of those at the milder end of the spectrum.

Stroke mortality is also a difficult subject especially when restricted to inpatients. Mortality can vary depending on whether those with milder strokes which could be managed as an outpatient are admitted and then counted. Mortality can be reduced by discharge to hospice or other care facilities, so patients do not die as inpatients. Mortality can be reduced by excluding those who are dying, however, this is less of a problem nowadays, and stroke units should take all patients irrespective of immediate survival. There have been concerns that appropriate end of life care can increase 30-day mortality in patients in whom a more aggressive policy would have delayed the death beyond 30 days. This is controversial when some units are judged on their 30-day mortality as a quality indicator of care. The most important determinant in death from a stroke is by far the stroke itself and then severe co-existing illness. The falling stroke mortality is excellent news, but this is offset by the fact that an ageing population will mean that the absolute number of patients with stroke will rise in years to come. It is key then that we have coordinated strategies in place to help to reduce stroke risk, mortality and morbidity.

References and further reading