First, it is a retrospective case-control study and is therefore susceptible to reporting bias, meaning that people with ALS may report their coffee consumption differently from controls.

FORBES: Does Coffee Drinking Really Protect Against Devastating Diseases?

In addition, case-control studies, such as the large INTERHEART study conducted in 52 countries, have provided valuable information.

FORBES: Do Smoking Bans Really Save Lives? If So, Whose?