"I must now do what's best for all concerned," Smith, who joined the band in 2001, said in a statement shared with PEOPLE

According to the Cleveland Clinic, Parkinsonism is an umbrella term that refers to several brain conditions — including Parkinson’s disease — that cause slowed movements, rigidity (stiffness) and tremors. Parkinson’s disease makes up about 80% of all Parkinsonism cases.

After being diagnosed with Parkinsonism, Steuart Smith is retiring as lead guitarist for the Eagles. The 72-year-old musician, who has acted as the “Hotel California” band’s co-lead guitarist for almost 25 years alongside Joe Walsh,