When all else fails, read the instructions. https://www.irs.gov/instructions/i1040sca#idm140545383582080
Limit on long-term care premiums you can deduct.
The amount you can deduct for qualified long-term care insurance contracts (as defined in Pub. 502) depends on the age, at the end of 2018, of the person for whom the premiums were paid. See the following chart for details.