Researchers also find fewer people of all ages dying of stroke
American Academy of Neurology
In older people,
researchers found declines in both ischemic stroke, caused by a blockage of
blood flow to the brain, and intracerebral hemorrhage, when a blood vessel
bursts inside the brain.
"Stroke is a leading cause of death and disability in the world," said study author Henrik Toft Sørensen, M.D., Ph.D., D.M.Sc., of Aarhus University Hospital in Aarhus, Denmark.
"Recent research on the incidence of stroke has been mixed, and some studies have reported an increase among young people. However, our research found no increase in stroke among young people, and it also found the incidence of stroke declining among older people, which is encouraging."
For the study,
researchers used national health care registries in Denmark to identify all
people in the country hospitalized with a first-time stroke between 2005 and
2018. They identified 8,680 younger adults age 18 to 49 who had a stroke during
that time, and 105,240 older adults age 50 and older.
Researchers calculated
yearly incidence rates for both ischemic and hemorrhagic stroke based on the
Danish population. They also calculated incidence rates based on age.
Researchers found the incidence rate of stroke in people 49 and younger remained steady over the course of the study, with around 21 cases of ischemic stroke per 100,000 person-years at the start and end of the study.
Person-years take into
account both the number of people in the study and the amount of time each
person spends in the study. For intracerebral hemorrhage, the incidence rate in
young people was around 2 cases per 100,000 person-years at the start and end
of the study.
Researchers found the incidence rates of stroke declined in people 50 and older over the course of the study, with 372 cases of ischemic stroke per 100,000 person-years at the start of the study and 311 cases at the end.
For intracerebral
hemorrhage, there were 49 cases per 100,000 person-years at the start of the
study and 38 cases at the end. However, stroke rates in people in their 50s
were stable, with most of the decline in people age 70 and older.
"The
decrease we found may be associated with better treatment of stroke risk
factors, such as hypertension and atrial fibrillation, as well as falling
smoking rates in the population," said Sørensen."
To determine
death rates, researchers calculated how many people died in the month after a
stroke and found rates declined in both younger and older people. For ischemic
stroke, 2.3% of younger people died one month after stroke at the start of the
study compared to 0.1% at the end. In older people, 8.2% died one month after
stroke at the start of the study compared to 6.0% at the end. For intracerebral
hemorrhage, rates among younger and older people declined as well.
"The improvements we found in survival rates are consistent with improvements in stroke care," said Sørensen.
"We also examined stroke severity and
found while mild strokes increased, the most severe cases declined. These
changes could be related to improvements in stroke awareness in the general
population as well as the care people receive for stroke, including in the
ambulance and emergency department prior to hospitalization. Such care has led
to faster and improved diagnostics, particularly regarding the mildest of
cases."
A limitation of
the study was that the data did not allow researchers to examine trends in some
subtypes of stroke. Another limitation was that the study was conducted in
Denmark so the results may not be the same for populations in other countries.