Complex sentence: In total, 12,763 men, 40-59 years of age, were enrolled as 16 cohorts, in seven countries, in four regions of the world (United States, Northern Europe, Southern Europe, Japan).
Split into simpler sentences: In total, 12,763 men, 40-59 years of age, were enrolled. The study included 16 cohorts, in seven countries, in four regions of the world (United States, Northern Europe, Southern Europe, Japan).