The second entry in our “Neurology and Men’s Health” series focuses on amyotrophic lateral sclerosis, or ALS. While both men and women can develop this devastating condition, men are more likely to develop ALS, and generally get it at a younger age. Rick Bedlack, MD, PhD, talks to us about the gender differences in ALS, how multidisciplinary programs like the Duke ALS Clinic can make a difference for people with ALS, and how our knowledge of ALS has advanced over the past 20 years.
ALS is more common among men than among women. How much more common is it, and do we know why this is? Are there any other gender-based differences in the symptoms, progression, or frequencies of “types” of ALS?
ALS is about 1 and a half times more common in men than it is in women. ALS also looks different in men. Men get the disease earlier in life (average age of onset in men is about 60 and in women is about 68). Men are more likely to have the disease start in the limbs, especially the arms, while women are more likely to have it start in the bulbar muscles (those involved in speech and swallowing. The prognosis of ALS is not different between the sexes, and survival time is similar in men and women with ALS.
We do not yet understand why these sex differences exist but they certainly suggest an influence of sex hormones on the disease. One possibility is toxicity from androgens (male sex hormones). At least 3 observations support this theory:
- There is a strong correlation between the distribution of androgen receptors and the pattern of specific cells affected in ALS.
- A mutation in the androgen receptor cause another motor neuron disease called Kennedy’s disease or spino-bulbar muscular atrophy.
- The ratio of index-to-ring-finger length (2D:4D), which is linked to prenatal androgen exposure, is also correlated with the risk of developing ALS.