William Henry Harrison

From Widipedia:

When Harrison took office in 1841 at the age of 68, he was the oldest man to become President - a record that stood for 140 years, until Ronald Reagan became President in 1981 at the age of 69. Harrison died thirty-one days into his term — the briefest presidency in the history of the office. He was also the first U.S. President to die while in office.

How did he die? The oath of office killed him.

He took the oath of office on March 4, 1841, an extremely cold and wet day. [2] Nevertheless, he faced the weather without his overcoat and delivered the longest inaugural address in American history. At 8,424 words, it took nearly two hours to read (even after his friend and fellow Whig, Daniel Webster, had edited it for length). He then rode through the streets in the inaugural parade, and later caught a cold, which then developed into pneumonia and pleurisy.

Pretty shitty way to go. But his grandson got to give it another shot:

Harrison's grandson, Benjamin Harrison of Ohio, became the 23rd president in 1889, making them the only grandparent-grandchild pair of presidents to date. In 1889, President Benjamin Harrison gave his inaugural address in the rain. Understanding his grandfather's mistakes, he asked his outgoing predecessor (and later his successor), Grover Cleveland, to hold an umbrella above his head, since he also delivered a long inaugural address.

Sometimes its better to just call in sick.