Genesis 5:5

and all the days that Adam lived were nine hundred and thirty years; and he died. That the patriarchs before the Flood lived to such a ripe old age was probably due to the fact that their bodies were not yet so filled with the many tendencies toward sickness which are now so prevalent; they were physically in much better condition than the people of the present time. Then also, as Luther remarks, God had special thoughts of kindness toward the world in having so many pious, wise, and holy men in the world at one time.