Sex Bias and NMOSD: Clinical Decision-Making

Neuromyelitis optica spectrum disorder (NMOSD) is an autoimmune disease. This means it is caused by the body mistakenly attacking itself. In NMOSD, the immune system attacks the central nervous system. A person's sex affects many parts of the body, including the immune system. This means that women and men diagnosed with NMOSD may have different experiences.1,2

How does sex impact the immune system?

Sex as a biological factor has widespread impacts. Sex impacts hormones, chromosomes, and sometimes environmental factors. These can in turn impact the immune system. Researchers see immune response differences between men and women over their entire lifespans.2,3

Because of these differences, men and women will have different responses to some conditions. For example, for men and women there are differences in:2

  • Chance of getting infectious diseases
  • Chance of developing autoimmune diseases
  • Outcomes and effectiveness of vaccines
  • Hormones, chromosomes, and the immune system

After puberty, men and women typically have different levels of certain hormones in the body. These hormones include estrogen, progesterone, and testosterone. Researchers have linked these hormones to different immune responses.2,3

The different hormones may explain some differences between men and women at certain ages. But these hormone levels can be the same in young children or older people. So hormones do not explain all the immune differences between sexes.2,3

Chromosomes are structures in our cells that hold our genes. Unlike hormones, chromosomes do not change over our lives. Women have 2 X chromosomes. Men have 1 X and 1 Y chromosome. There are certain genes that affect the immune system that only exist on X chromosomes. So this may also explain some differences.2,3

How does sex impact NMOSD?

About 4 out of 5 people with autoimmune diseases are women. And about 9 out of 10 people diagnosed with NMOSD are women. Women diagnosed with NMOSD are also more likely to have a relapsing form.2,3

Men with NMOSD are more likely to be diagnosed at an older age than women. The first symptom men have is more likely to be transverse myelitis. This causes weakness in or difficulty moving the arms and legs.1,3

We still do not fully understand the differences between immune response for men and women, especially with NMOSD. More research is needed to explore the link between sex and NMOSD. We also do not know how some sex-related factors impact NMOSD. For example, there is not much research on pregnancy and NMOSD.2,3

Impacts of sex gender and on care

Men and women can also have different healthcare experiences. Research shows that it can take women longer to receive diagnosis and treatment than men. These differences are called gender inequality in healthcare. There is limited research on NMOSD and gender inequality in healthcare. But, because this inequality is present in medicine, it can impact people with NMOSD.3,4

We cannot prevent biological differences in our immune system. But we can try to prevent gender inequality. For example, we can:4

  • Implement standardized practices across sex
  • Encourage more women to become doctors
  • Provide woman-specific screenings
  • If you are worried about your NMOSD care, try talking to your doctor.

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