Is Stroke Trending Younger?
Hospitalizations for acute ischemic stroke in younger people appeared to rise over the past 10 years, but whether stroke prevalence is surging in this group remains unclear, researchers reported.
In an analysis of data from the National Inpatient Sample, there were almost 30,000 more hospitalizations for acute ischemic stroke in people under 65 in 2012 than there were in 2003, Mary George, MD, MSPH, of the CDC, and colleagues reported online in JAMA Neurology.
But population growth alone accounts for 15,000 of those deaths, and changes in diagnostic classification system and coding may account for the increase, according to editorialists James Burke, MD, and Lesli Skolarus, MD, of the University of Michigan.
"It is startling that in a country that spends almost 20% of the largest gross domestic product on the planet on healthcare, we cannot say with confidence whether the fifth leading cause of death in the United States is increasing or decreasing in the young," they wrote. "Yet, that is precisely our state of affairs."
Burke and Skolarus wrote that the CDC investigators "should be commended for their effort to help resolve this uncertainty," but noted that questions remain.
George and colleagues looked at data from the Nationwide Inpatient Sample, a nationally representative database of hospital discharge abstracts. The 2003-2004 set included more than 362,000 hospitalizations, and the 2011-2012 set included almost 422,000 hospitalizations.
They found that acute ischemic stroke hospitalization rates increased significantly for both men and women ages 18 to 54. Specifically, rates have almost doubled for men ages 18 to 34 and 35 to 44 years since 1995-1996, they noted.
Also, they found a 42% relative increase among men and a 30% relative increase among women ages 35 to 44 in stroke hospitalization rate over the full decade.
At the same time, the prevalence of stroke risk factors among those hospitalized for acute ischemic stroke increased. The range of absolute increase in prevalence of stroke risk factors among men and women 18 to 64 years of age hospitalized for ischemic stroke was as follows:
Lipid disorders: 12%-21%
Tobacco use: 5%-16%
Young adults admitted for stroke had nearly twice the rate of stroke risk factors compared with their counterparts in the general population, the researchers reported. Notably, among men 18 to 34 years of age, the prevalence of hypertension increased from 34% to 41%, and the prevalence of lipid disorders nearly doubled from 15% to 29%, they said.
The observed increases in both stroke-related hospitalizations and vascular risk factors "confirms the importance of focusing on prevention in younger adults," George and colleagues wrote.
Burke and Skolarus reiterated their concerns regarding the reported increases in risk factor prevalence, noting that similar diagnostic and coding factors may be involved in calculation of both stroke and risk factor prevalence. In particular, they noted that the increase in hypertension was not reflected in a similar expected increase in intracerebral hemorrhage.
Indeed, hospitalization rates for intracerebral hemorrhage and subarachnoid hemorrhage remained stable except for declines among men and non-Hispanic black patients ages 45 to 54 with subarachnoid hemorrhage, George and colleagues reported.
Burke and Skolarus noted that other factors that could account for the increase could be greater use of magnetic resonance imaging (MRI) and changes to the diagnostic classification system from a time-based to tissue-based definition of TIA, such that some events diagnosed as TIA in 2003 would have been diagnosed as ischemic stroke in 2012.
Changes in coding practices as part of a general trend toward more accurate coding over time – coupled with hospitals' increasing cost-fueled incentive to select a stroke diagnosis over a TIA diagnosis – may also have contributed to increased identification of strokes, they noted.
Study limitations included the potential over-representation of a single stroke when it causes more than one hospitalization; that neither stroke severity nor cause were identified; that high rates of imaging used among younger adults by 2005 likely reduces the impact of MRI findings on the observed increase in stroke incidence; and the lack of information on family history or the use of estrogen-based medications.