Multiple sclerosis is a progressive degenerative demyelinating central nervous system disorder. Its presentation ranges from mild to significantly debilitating. Although it is believe it is primarily an auto immune disease, there are several contributing factors that may increase the risk of multiple sclerosis.

MS is most frequently diagnosed in adults aged 20 to 50, with a peak onset around 30–32 years, though it can occur at any age. Women are 2 to 3 times more likely to develop MS than men.

MS prevalence increases with distance from the equator, showing higher rates in northern Europe, Canada, the northern US, New Zealand, and southeastern Australia (high-latitude regions). This geographic gradient is linked to lower sunlight exposure, which correlates with reduced vitamin D levels, a suspected environmental risk factor.

Interestingly, hot weather worsens MS symptoms for many people (60-80%) because heat slows nerve signals in demyelinated nerves, causing temporary fatigue, weakness, vision issues, or balance problems (known as Uhthoff's phenomenon). While symptoms usually improve with cooling, managing heat through cool baths, light clothes, hydration, and avoiding peak sun is crucial, as even slight core temperature rises can trigger flares.