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Cerebral venous thrombosis (CVT) has not only become more common in recent years but also changed in demographics, researchers found.

The incidence of new CVT cases in Florida and New York rose from 13.9 per million people in 2006 to 20.0 per million people in 2016 (P<0.001), reported Fadar Otite, MD, ScM, of the State University of New York Upstate Medical University in Syracuse, and colleagues in a paper .

Age and sex distribution of incident cases in the two states is very similar to that of the entire U.S., so the upward trajectory of CVT may be generalizable to national trends, according to the group.

"Older studies estimate the annual incidence of CVT as between 2 to 5 cases per million population but studies providing these estimates relied on data that predated the widespread use of for CVT such as CT and magnetic resonance venography and are therefore likely limited by underdetection," the authors wrote.

Additionally, the proportion of women ages 18-44 years among CVT hospitalizations remained unchanged over time, while older women and men of all ages accounted for an increasing number of cases.

"Whether real or artefactual from improved detection, rising incidence implies that CVT is either a growing or previously unrecognized problem in males and older females and no longer just a disease of young females alone," the investigators said.

Otite and colleagues also found more CVT cases in Black people compared with other racial and ethnic groups.

Their retrospective cohort study identified 5,567 new cases of CVT in Florida and New York from 2006 to 2016, according to those state inpatient databases. New cases of CVT were defined as a person's first hospitalization for CVT, identified from ICD codes.

The estimated 57,315 CVT admissions in the U.S. from 2005 to 2016 represented 0.66% of all adult hospitalizations for any cerebrovascular disease over this time. CVT admissions accounted for a rising proportion of stroke admissions in particular (from 0.47% in 2005 to 0.80% in 2016, P<0.001).

The study findings confirm the rising CVT incidence previously reported in Australia and the Netherlands.

Advances in CVT detection aside, another explanation for the increased incidence could be changes in the prevalence of CVT risk factors.

"In this study, we documented a marked increase in the proportion of CVT hospitalizations with comorbid codes for brain tumor, cancer and inflammatory diseases. Prevalence of obesity, a possible emerging risk factor for CVT when , also more than doubled in CVT hospitalizations over time," Otite's group reported.

Notably, the number of pregnant and postpartum women hospitalized with CVT dropped sharply over the study period.

"While we also have no clear explanation for this intriguing finding, it is possible that changes in obstetric practices over the last decade including recommendations for utilization of aspirin to prevent pre-eclampsia in at-risk patients may also have inadvertently led to a decrease in pregnancy and postpartum-associated CVTs in some otherwise at-risk patients," according to the authors.

They acknowledged several limitations of the study, including its reliance on hospital databases that would have missed asymptomatic or mild cases of CVT. Moreover, the modest sensitivity of ICD codes for CVT diagnosis might have meant that many cases were not captured.

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