Complex sentence: An estimated 50% of men have histologic evidence of BPH by age 50 years and 75% by age 80 years; in 40-50% of these men, BPH becomes clinically significant.
Split into simpler sentences: An estimated 50% of men have histologic evidence of BPH by age 50 years and 75% by age 80 years. In 40-50% of these patients, BPH becomes clinically significant.