Which of the following is a risk factor for cataracts?

The correct choice highlights a significant risk factor for the development of cataracts: smoking. Research has consistently shown that smoking increases the risk of cataract formation due to the oxidative stress it places on the eyes, which can lead to the clouding of the lens. The harmful substances in tobacco smoke can damage the proteins in the lens, contributing to the opacity associated with cataracts.

In contrast, the other options do not present established connections to cataract development. While excessive exercise is generally considered beneficial for overall health and well-being, it does not have a direct link to cataracts. Low cholesterol levels are usually associated with a reduced risk of various health issues, not an increased risk for cataracts. Frequent swimming poses minimal risk related to cataract development, as long as proper eye protection is used, since the pool water does not directly contribute to lens clouding. Therefore, smoking stands out as a clear and documented risk factor for cataract formation in medical literature.