Where an occupational disease, as defined by section 23-901, paragraph 13, subdivision (c), is aggravated by any other disease or infirmity not itself compensable, or where disability or death from any other cause not itself compensable is aggravated, prolonged, accelerated or in anywise contributed to by an occupational disease, the compensation payable under this chapter shall be reduced and limited to such proportion only of the compensation that would be payable if the occupational disease were the sole cause of the disability or death, as such occupational disease as a causative factor bears to all the causes of such disability or death.
A.R.S. § 23-901.05