Infirmity

[Luis Fok]

The state of being infirm; feebleness; an imperfection
or weakness; esp., an unsound, unhealthy, or debilitated state; a
disease; a malady; as, infirmity of body or mind.

[Couch Potatoe]

Physical or mental weakness.

[Gregory]

a state of being [weak] or [ill] over a long period of time, especially one caused by [old age]

[Tariq Zaki]

illness, especially for long periods or because of old age: