Brain Bleeds: How Biological Sex Affects Severity and Outcomes

Bleeding in the brain can have dire consequences, and the size and location of these intracerebral hemorrhages may vary depending on biological sex, new research shows.

The study, led by Cyprien Rivier, MD, MSc, associate research scientist in the Department of Neurology, looked at over 4,000 people who were hospitalized for strokes caused by brain bleeding. It concluded that men are more likely than women to experience hemorrhages that develop in deeper parts of the brain. Brain bleeds in men also tended to be larger and at a higher risk of expanding. However, men are also more likely than women to have better outcomes while recovering from a stroke.

The research was recently published in Annals of Neurology and was supported by a Ralph L. Sacco Scholarship in Brain Health by the American Heart Association and American Academy of Neurology.

Strokes are among the leading causes of death and disability in the United States. Intracerebral hemorrhages, a type of hemorrhagic stroke, occur when blood vessels in the brain spontaneously burst.

Scientists have long suspected that a person’s sex may play a role in how brains bleed. To test this, Rivier and colleagues collected patient information from four large-scale studies on intracerebral hemorrhaging, including three clinical and one observational study. The researchers then compared hemorrhage size, location, and outcomes between men and women.

The data consistently showed that men were more likely than women to develop hemorrhages in deeper parts of the brain. Deep bleeds are more dangerous than bleeding in brain lobes nearer to the skull because they are located closer to parts of the brain involved in critical functions like breathing and motor functions. Male patients also experienced larger initial bleeds that were at a greater risk of worsening compared to their female counterparts.

Men might have larger bleeds than women because they are more likely to have high blood pressure, which would lead to more blood entering the brain. Another hypoethsis is that estrogen, which is involved in clotting and exists in high concentrations in women, could help patch up burst vessels more quickly in women than in men.

While men faced a worse set of initial risks, follow-up medical care three and six months after their strokes showed that they scored better on a death and disability scale than women. Rivier isn’t sure why this is, but noted that men in the study were, on average, four years younger than women, with a mean age of 60. This may have helped contribute to easier recoveries.

Furthermore, men “tend to receive more aggressive care when they are in an intensive care unit,” he says. Bias that favors men might mean that clinicians grant them more resources—both in time and attention—while in the hospital than women. Men might also be more likely to demand aggressive life-saving treatment, says Rivier.

Indeed, in the clinical trials in which all participants received standardized care and attention, the team found no evidence of sex differences in health outcomes. It was only in the observational study, which more closely mimics everyday care, that women had worse outcomes.

Rivier hopes that researchers and doctors will note that sex does affect the severity and outcome of brain bleeds. But, he adds, it’s also important to keep in mind that sex biases may influence medical care and can shape how severely those bleeds impact their patients.