Secular trends in growth of my thumbnail are reported. Various observations, including slowing of the rate of growth with infections, are recorded. The slowing of the rate of growth has progressed in somewhat irregular phases. This is a phenomenon that most people observe if they care to introspect themselves as they participate in the aging process. The average daily rate of growth has varied from 0.123 mm per day when I was 32 to 0.100 mm when I was 61.
Bean WB. Nail Growth: 30 Years of Observation. Arch Intern Med. 1974;134(3):497-502. doi:10.1001/archinte.1974.00320210107015