In case of disability or death from silicosis, complicated with tuberculosis of the lungs, income benefits shall be payable as for uncomplicated silicosis, provided, that the silicosis was an essential factor in causing such disability or death. In case of disability or death from silicosis complicated with any other disease, or from any other disease complicated with silicosis, the income benefits shall be reduced as provided in section 72-406[, Idaho Code].