Complex sentence: People aged 18--29 were the most likely to identify as non-heterosexual (15%) followed by those aged 30--49 (10%); only 5% of the population aged 50 or more consider themselves gay or bisexual.
Split into simpler sentences: People aged 18--29 were the most likely to identify as non-heterosexual (15%), followed by those aged 30--49 (10%). Only 5% of the population aged 50 or more consider themselves gay or bisexual.