Allah tells us that the longer the son of Adam lives, the more he becomes weak after being strong, and incapable after being able and active

This is like the Ayah:

اللَّهُ الَّذِى خَلَقَكُمْ مِّن ضَعْفٍ ثُمَّ جَعَلَ مِن بَعْدِ ضَعْفٍ قُوَّةٍ ثُمَّ جَعَلَ مِن بَعْدِ قُوَّةٍ ضَعْفاً وَشَيْبَةً يَخْلُقُ مَا يَشَآءُ وَهُوَ الْعَلِيمُ الْقَدِيرُ

In the last of the verses cited above, it was said: وَمَن نُّعَمِّرْ‌هُ نُنَكِّسْهُ فِي الْخَلْقِ أَفَلَا يَعْقِلُونَ (And whomsoever We give long life, we reverse him in creation. Do they then not have sense?). The word: نُّعَمِّر (nu'ammir: We give a long life) in this verse has been derived from: تَمِیر (ta` mir) which means to prolong years of life. And the word: نُنَكِّسْهُ (nunakkishu) is a derivation from: تَنکِیس (tankis) which means to reverse, invert or turn upside down. In this verse, Allah Ta’ ala has described yet another manifestation of His perfect power and eloquent wisdom in that every living being lies under the free will of Allah Ta’ ala all the time. The process of nature is going on. The thing started from a lifeless drop. Wrapped with three layers of darkness in the womb of the mother, that which came to be was this essence of the universe, and a small world in its own right. Countless was the number of most delicate mechanisms that were embedded into its life form. Then it was made to come alive with the infusion of the spirit. After having been nourished and grown for nine months inside the womb of the mother, a perfect human being came into this world. Of course, perfect it was, but the body it had was weak. Nature took care of that by placing in the breast of the mother food that would suit an infant's physical requirement. This gave it the gradual supply of needed energy. From that time to the time of youth, passed many stages and then came a strong body at its total bloom. Then came claims of the power thus acquired and rose the desire to defeat every conceivable adversary.

But, that was not the end. When the creator and master of this new aspirant into the world decided otherwise, all these strengths started waning. Even the decline was not sudden. It took time. There were countless stages. Finally, came the fag end of the years of life. Once there, just imagine, has this person not reached back into the stage of one's childhood. Habits started changing. Reflexes became different. Things that used to be the dearest started appearing hateful. What was comfort once turned into suffering. This is what the Qur'an calls "tankis," that is, being turned upside down. One trusts what one sees with one's own eyes and what one hears with one's own ears in the life of this world. This too does not remain trustworthy during the later years of old age. Clearly understanding what is being said becomes difficult because one becomes hard of hearing. The same thing happens to the sense of sight that becomes weak. One cannot see well enough. The classical Arab poet, al-Mutanabbi has said: