No compensation shall be payable for an occupational disease if the employee at the time of entering into the employment of the employer by whom the compensation would otherwise be payable, or thereafter, wilfully and falsely represents in writing that he has not previously suffered from the disease which is the cause of the disability or death. Where an occupational disease 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 any way contributed to by an occupational disease, the compensation payable shall be a 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, bearing to all the causes of such disability or death, such reduction in compensation to be effected by reducing the number of weekly payments or the amounts of such payments, as under the circumstances of the particular case may be for the best interest of the claimant or claimants.