More Data Suggest Stroke Rates Rising in Younger Adults

April 12, 2017

Another study has suggested stroke rates are increasing in younger adults, with the authors calling for more effort in preventing and controlling stroke risk factors among young, working-age adults.

However, there is uncertainty about whether the results reflect a real crisis in this age group or are actually a consequence of changes in the measurement system.

The study, published online in JAMA Neurology on April 10, was conducted by a team led by Mary G. George, MD, from the Centers for Disease Control and Prevention, Atlanta, Georgia.

They analyzed International Classification of Diseases codes on hospitalization data from the National Inpatient Sample (a large and nationally representative administrative database of hospital discharge abstracts) to look at stroke rates and the prevalence of risk factors among adults aged 18 to 64 years from 1995 to 2012.

Results showed that acute ischemic stroke hospitalization rates increased significantly for both men and women in the 18- to 54-year-old age group, with almost 30,000 more stroke hospitalizations in 2012 than in 2003, and rates almost doubled for men aged 18 to 44 years.

In contrast, for men and women aged 55 to 64 years, ischemic stroke rates have not changed from 2003 to 2004. Also, hospitalization rates for intracerebral hemorrhage did not change from 2003-2004 to 2011-2012 among those aged 18 to 64 years.

The researchers also found that the prevalence rates of risk factors (such as hypertension, lipid disorders, diabetes, tobacco use, and obesity) in both men and women aged 18 to 64 years experiencing ischemic or hemorrhagic stroke have continued to increase during the time studied, with a near doubling in the percentage of those with three to five risk factors from 2003-2004 to 2011-2012.

"We found that the prevalence of hypertension among men aged 18 to 34 admitted with an acute ischemic stroke increased from 1 in 3 to 40%, and increased from 1 in 4 to 1 in 3 among females," Dr George commented to Medscape Medical News. "Also, two thirds of males and 57% of females ages 35 to 44 had hypertension, while about 3 out of every 4 aged 45 to 54 had hypertension. This is important, as we know that the prevalence of hypertension in the whole adult population is 29%."

She added that the incidence of diabetes was also much higher in these young adults experiencing ischemic stroke than in the general population. "We found that about 30% of these stroke patients aged 35 to 44 had diabetes and about 40% of those aged 45 to 54. This compares to a prevalence of 9% in the general US adult population."

The authors note that their findings are consistent with other recent studies that have also suggested an increased rate of stroke in younger adults.

"These findings of increasing [acute ischemic stroke] hospitalization rates among those aged 18 to 54 years and no change among those aged 55 to 64 years reveals an inflection point in stroke hospitalization rates when compared with findings of decreasing ischemic stroke hospitalization rates among those aged 65 to 74 and 75 to 84 years, and a nonsignificant decline among those 85 years and older," they write.

They suggest that their findings may reflect better hypertension control over time among elderly people compared with younger adults.

They point out that "[t]he significant increases in ischemic stroke hospitalizations and associated traditional stroke risk factors...should serve as a call to action to focus on improving the health of younger adults."

They conclude: "Preventing and controlling stroke risk factors among young working-age adults can save lives, reduce disability, decrease societal health care costs, and improve the quality of life for hundreds of thousands of Americans and their families. Identifying the high and rising prevalence of stroke risk factors among younger adults presenting with acute stroke should prompt a sense of urgency among younger adults, public health practitioners, clinicians, and policymakers to engage adolescents and their families, as well as younger adults, to identify and treat stroke risk factors and promote opportunities that allow for healthy lifestyles to prevent the tragedy of stroke at such early ages."

Questions on Measurement

In an accompanying editorial, James F. Burke, MD, and Lesli E. Skolarus, MD, from the University of Michigan, Ann Arbor, say that: "If these findings represent a true epidemiologic trend, understanding the reasons underlying this trend and seeking to reverse it should be a leading priority of the stroke community." But they add: "However, it is not yet clear whether such urgent action is needed."

The editorialists point out that the uncertainty arises because key measurement issues could have affected the way strokes are recorded for administrative purposes.

They say these include changes to the diagnostic classification system, which now labels more events as strokes that would previously have been categorized as transient ischemic attacks; the increased use of magnetic resonance imaging picking up previously undiagnosed subtle clinical events; and financial pressures causing possible changes in coding practices (as hospitals have a financial incentive to select a stroke diagnosis over a TIA diagnosis and the relative importance of this incentive may have increased as the costs of stroke care increased).

They also suggest that the increase in risk factors over time could reflect more accurate coding as part of a general trend toward increasingly accurate coding practices over time or changes in the definitions of risk factors.

"It is startling that in a country that spends almost 20% of the largest gross domestic product on the planet on health care, we cannot say with confidence whether the fifth leading cause of death in the United States is increasing or decreasing in the young," Dr Burke and Dr Skolarus write. "Yet, that is precisely our state of affairs."

They add that developing better surveillance systems should be a priority of the stroke research community. This could involve collecting more widespread epidemiologic data, harmonizing and building cooperation between existing epidemiological studies, and developing more reliable administrative- or electronic medical record–based surveillance systems.

In response to these comments from the editorialists, Dr George provided additional information suggesting the increase in stroke seen in her data was not purely because of imaging or reclassification changes.

She noted that the Greater Cincinnati Northern Kentucky Stroke Study concluded in 2015 that the increased use of magnetic resonance imaging has had little effect on the incidence or event rates for stroke, and the Minnesota Stroke Survey found that 98% of stroke cases were already using CT for diagnosis by 2000.

She also pointed out that there was an update to the definition of stroke published by the American Heart Association/American Stroke Association in 2013, which incorporated both clinical findings and neuroimaging in the diagnosis, but the current study used data collected before this publication.

"There was also a change to the definition of [transient ischemic attack] in 2009. If this had any effect on our study, it would likely manifest itself in the change from 2009-2010 to 2011-2012. However, we found a steady increase in ischemic stroke among those ages 35 to 44 from 1995-1996 through 2011-2012 without a sudden increase over time," Dr George added.

"Further, among those ages 45-54 we saw a steady increase from 2003-2004 through 2011-2012; again, we did not see a sudden increase."

The US Centers for Disease Control and Prevention supported this study as part of the official duties of the authors. No external funding was used. The authors have disclosed no relevant financial relationships.

JAMA Neurol. Published online April 10. Article full text, Editorial full text

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