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Sex Differences in Multiple Sclerosis
Multiple Sclerosis – Sex Differences – Pregnancy – Genetic Factors
Sex Differences in Multiple Sclerosis
Relapsing-remitting form of multiple sclerosis is more common in women. Current ratio is 3.2 to 1. There is a steady rise in female incidence of MS over years while male incidence remains stable.
Two hundred years ago multiple sclerosis was believed to be more common in males. In the remote past the data was most likely biased by believes that the symptoms in females were caused by hysteria.
Whether continuing trend in recent years is caused by the true increase in incidence in women, or it is due to better diagnosis is not clear.
Primary progressive form of MS incidence remains stable and it is pretty much equal in both genders.
The most common age of onset for relapsing-remitting multiple sclerosis is between 15 and 45 years with mean age 28 to 31 years. Females, on average, develop this form of MS a few years earlier than males.
Women develop irreversible disability due to MS somewhat later than males.
Conversion to secondary progressive MS, if occurs, is typically around 40 to 49 years has similar rates in both sexes.
Female gender is a risk factor for transformation of optic neuritis into clinically definite multiple sclerosis. Neither gender is at higher risk of transformation in radiologically isolated syndrome or in other forms of clinically isolated MS syndrome.
Studies did not reveal any significant sex differences on MRIs or in pathological studies.
Sexual dysfunction affects majority of MS patients. Early in the disease the main reason for sexual dysfunction is due to decreased libido, psychological, and social issues in both sexes.
In advanced disease the problem is also related to neurological symptoms. Sexual dysfunction due to neurological symptoms is more common in males due to insufficient erection, which correlates with lower limb, bladder, and bowel involvement.
Women, however, might be able to have orgasm even in advanced disease. Inability to reach orgasm in women is due to decreased sensation from erogenous zones, decreased vaginal sensation and lubrication.
Pregnancy and Family Planning in Multiple Sclerosis
Parents are often concerned about transmitting “multiple sclerosis genes” to their children. The cause of MS is multifactorial, so there is no single gene or factor responsible for this disease.
Future parents have to be aware that even though the chance of MS in children brought to parent(s) with multiple sclerosis is increased, it is still low.
Having a single parent or a sibling suffering MS carries a risk of multiple sclerosis between 3% and 5%. The risk is 0.2% in general population. Having both parents with MS raises the chance to 30.5%. Similar rate is observed in identical twins.
There are no genetic tests currently available to assess the chance of multiple sclerosis in a particular person.
Family planning is important because the effect of the disease modifying drugs of the fetus is not well studied. Oral contraceptives appear having no effect on MS course. They have to be used with caution in women with limited ability to ambulate due to the risk of deep vein thrombosis.
The effect of pregnancy on relapsing-remitting MS is rather beneficial. There is a 70% relapse rate reduction during pregnancy. There is an increased relapse rate during the first trimester after delivery with return to average rate thereafter. Overall pregnancy does not carry deleterious effect on disability progression.
Breastfeeding has been shown to be associated with a substantial decrease in MS relapse rate. Use of interferons and glutiramer acetate is considered save during breastfeeding.
Multiple sclerosis doesn’t have any untoward effect on the fetus. There is no evidence of increased chance birth defects or miscarriages.
In general, disease modifying treatments have to be avoided during the first trimester. Interferons cause spontaneous abortions in animals. It appears they do increase the chance of miscarriage in humans. Copaxone appears to be safer based on animal studies, but its safety in humans has not been proven.
MRI has never been proven having negative effects on the fetus. Nevertheless, MRI is not recommended in the first trimester.
Safety of Gadolinium (MRI contrast) in humans has not been established and it has to be avoided during pregnancy.
Menopause carries some risk of MS worsening. Considering temperature regulation issues during perimenopause (hot flashes) and MS symptoms sensitivity to the body core temperature, it is not surprising that hormone replacement improves neurological symptoms.
Hormone replacement may have a great importance due to the increased risk of osteoporosis caused by frequent steroid use during MS exacerbations over the disease lifetime.