ROCHESTER, Minn. – Mayo Clinic operating income fell $100 million in the first three months of 2022 while expenses climbed. The revenue totaled $142 million  compared to a record $243 million a year earlier. The statistics were released as a government requirement because Mayo relies on municipal bonds to finance expansion projects. While revenue was down, costs rose. Salaries and benefits rose $155 million, supplies $188 million.