Multiple sclerosis usually occurs in which type of climate?

Multiple sclerosis (MS) is a chronic autoimmune disease that affects the central nervous system, and its occurrence has been observed to correlate with geographic and climatic factors. Research indicates that MS is more prevalent in regions that have cooler climates, particularly those further from the equator. This association may relate to environmental and genetic factors that influence vitamin D levels, which have been implicated in immune system regulation and the onset of autoimmune diseases.

In cooler climates, populations tend to have lower exposure to sunlight, leading to decreased vitamin D synthesis, which is thought to play a role in MS pathogenesis. Therefore, the higher incidence of multiple sclerosis noted in temperate regions supports the idea that MS tends to occur more frequently in these cooler climates, making this the correct choice in the context of the question.