Deductible medical and dental expenses were limited, based on a percentage of AGI. The definition of expenses includes payments for certain long-term care insurance premiums and for the unreimbursed cost of certain long-term care of a chronically ill individual.
For additional information about the return filing requirements, see the annual reports, Statistics of Income-Individual Income Tax Returns at https://www.irs.gov/uac/soi-tax-stats-historical-data-tables.
U.S. Department of the Treasury. Internal Revenue Service, Individual Income Tax Filing: Itemized Deductions: Medical and Dental Expense [IMZDDMDE], retrieved from FRED, Federal Reserve Bank of St. Louis; https://fred.stlouisfed.org/series/IMZDDMDE, March 17, 2018.