Complex sentence: Onset of symptoms generally occurs later in life, near the age of 60, and the prevalence of the disorder among the elderly is about 2-4% (Roth, 1955; Almeida, 1992).
Split into simpler sentences: Onset of symptoms generally occurs later in life, near the age of 60. The prevalence of the disorder among the elderly is about 2-4% (Roth, 1955; Almeida, 1992).