4. The physical or mental disability for which a plan may, within the meaning of paragraph b of section 38 of the Act, allow a member to replace the deferred annuity by a payment or a series of payments, is disability of such a nature as to considerably shorten his life expectancy. This definition does not apply to the replacement of the deferred annuity by a disability life annuity.
R.R.Q., 1981, c. R-17, r. 1, s. 4.