Complex sentence: He attempted to keep his condition private, but by 1883 rumors of his illness began to circulate; he had become thinner and more aged in appearance, and struggled to keep the pace of the presidency.
Split into simpler sentences: He attempted to keep his condition private, but by 1883 rumors of his illness began to circulate. By that time he had become thinner and more aged in appearance, as well as less energetic in keeping up with the demands of the presidency.