BRICKLEY, Justice.
In this workers' compensation case, we address one major question: Should the rule of Kleinschrodt v. General Motors Corp, 402 Mich. 381, 263 N.W.2d 246 (1978), reh. den. 402 Mich. 965 (1978), governing the proper interpretation of the one-year-back rule, M.C.L. Sec. 418.833(1); M.S.A. Sec. 17.237(833)(1), and, as applied by analogy, the two-year-back rule, M.C.L. Sec. 418.381(2); M.S.A. Sec. 17.237(381)(2), be modified or overruled? In addition, we consider the defendant-appellant's arguments regarding the Workers' Compensation Appeal Board finding of a work-related disability.
The Court of Appeals summarized the evidence presented to the hearing referee:
"Plaintiff commenced his employment with defendant at its Fisher Body plant in Grand Blanc on April 23, 1953, and, in October, 1956, he began to work as a die setter. Plaintiff described his duties as a die setter as being extremely strenuous. The job included prying heavy dies with six-foot bars. Sometime during the early 1960's, plaintiff was pulling a bar and moving a die into place when he felt a snap and pull in his back. He went to the first aid station, where he was given heat treatments, and he did not miss any time from work because of the injury.
"Plaintiff claimed that following the injury he continued to have pain in his back. The pain became so intense that, in 1963, he was forced to have surgery. Plaintiff recuperated for six months before returning to his job as a die setter on October 18, 1963. The surgery was successful to the extent that plaintiff did not require additional time off from work because of the injury. Plaintiff, however, claimed that the pain continued.
"During cross-examination, plaintiff explained that his health insurer had paid some of his surgical bills and that he had paid the balance. The defense entered into evidence a letter written by plaintiff to his health insurer which stated that his back trouble was not related to his employment. Plaintiff identified the writing and signature as his own, but stated that he did not remember writing the letter.
"In March, 1967, plaintiff requested a transfer to the position of crane operator because he believed that this job would be less injurious than working as a die setter. This request was granted. Plaintiff stated that in order to get into the crane he had to climb a forty-foot ladder. He estimated that he climbed up and down the ladder 12 to 15 times a day and that the pulling involved in climbing the ladder put a strain on his back. Moreover, in order to get signals from the workers on the ground, plaintiff had
to stand up and lean over the cab which placed additional stress on his back.
"Roland Willis, who supervised plaintiff at the Fisher Body plant, contradicted plaintiff's testimony as to the operation of the cranes. Willis stated that plaintiff would operate only one or two cranes a day, necessitating only a limited amount of climbing. In addition, the crane could be turned 180 degrees, enabling the operator to see down from the side of the cab without leaning out over the front of the machine. Willis further testified that plaintiff was only in the cabs about four hours a day and that the only reason for him to stand up was to stretch his legs if they got tired.
"On December 5, 1966, plaintiff again injured himself when he slipped on icy pavement in the plant's parking lot. Plaintiff fell on his tailbone and experienced shooting pains in his hip and right leg. Plaintiff went to the plant's first aid station and informed them of the slippery conditions in the parking lot. Although plaintiff claimed that he continued to have pain in his right leg because of the accident, he admitted on cross-examination that his right leg had been previously injured during World War II. At the time of the hearing, plaintiff was receiving compensation from the government for the injuries to his right leg. Following the slip and fall, GMC arranged for plaintiff to see Dr. Harris about the resulting pain. The plant's records reveal that on December 9, 1966, plaintiff reported that he was 'much improved' and requested that the appointment be cancelled. At the hearing, plaintiff denied that he had ever made such a request.
"Plaintiff did not receive any further medical treatment until July, 1973, when he suffered a ruptured appendix. During plaintiff's 90-day convalescence following surgery, he experienced an exacerbation of the pain in his back and leg. In addition, plaintiff began feeling brief transient pains in his chest. Notwithstanding his physical infirmities, plaintiff returned to work as a crane operator. He remained on the job for about a month, but was forced to leave because of the pain in his leg. Plaintiff went back to Dr. Herzog, the physician who originally operated on plaintiff's back, for an examination. Dr. Herzog took x-rays and conducted a myelogram, ultimately determining that plaintiff required additional surgery on his lower back. Plaintiff testified that, even after this surgery, the pain in his back was too intense to allow him to continue as a crane operator. Plaintiff admitted, however, that his intervening heart disease also prevented him from returning to work.
"Following plaintiff's last day of work at General Motors on July 13, 1973, plaintiff was examined by several physicians. Dr. Van Brocklin concluded that plaintiff could return to work provided he was placed in a 'sit-down' job. Van Brocklin did not believe that it was possible for plaintiff to continue as a crane operator because climbing the ladder might affect plaintiff's heart condition. Van Brocklin noted that there might also be some pain in plaintiff's back during the climbing.
"Dr. Irving Young's examination revealed that plaintiff suffered no limitation of movement because of back pain. The x-rays showed a narrowing of the disc space and anterior spurring that might have been precipitated by the strenuous nature of plaintiff's work in the early 1960's. Young found no evidence that plaintiff's back injury was further aggravated by his employment.
"Dr. Leon Friedman determined that plaintiff could not participate in significant physical activity because of his advanced cardiovascular disease. Friedman believed, however, that plaintiff could perform satisfactorily in a sedentary or semi-sedentary job. Although Dr. Friedman's examination focused on plaintiff's heart ailment, the doctor noted that plaintiff continued to complain of back pain.
"Although plaintiff originally claimed that his employment caused aggravation
to his back, appendix, heart, and lungs, he deleted all claims except those relating to his back. The disability award was accordingly based solely on the aggravation of his back condition." Howard v. General Motors Corp, 132 Mich.App. 639, 641-644, 348 N.W.2d 286 (1984).
The plaintiff's petition for hearing by the Bureau of Workers' Compensation was filed June 24, 1977. After a hearing on August 21, 1979, the referee issued his decision on August 27, 1979, awarding plaintiff compensation for aggravation of his back condition as of his last day of employment, July 13, 1973. The hearing referee
"determined that plaintiff was disabled due to the aggravation of back condition causally related to his employment. Plaintiff was credible and proved his disability by a preponderance of the evidence."
Defendant appealed to the Workers' Compensation Appeal Board on October 8, 1979. Except for a modification of the compensation rate and interest award, the board affirmed the plaintiff's award. The board concluded that a 1973 work-aggravated disability was supported by the evidence.
In addition, as to defendant's assertion of the two-year-back rule of M.C.L. Sec. 418.381(2); M.S.A. Sec. 17.237(381)(2), the board held that
"[b]y its failure to invoke the two-year-back rule of Section 381(2) before the trial court, defendant has waived that non-jurisdictional affirmative defense, akin to a statute of limitations. It cannot thus raise that issue for the first time before the appeal board. Kingery v Ford Motor Co, 116 Mich App 606, 613-615 (1982), see also Kleinschrodt v General Motors Corp, 402 Mich 381, 384, 263 N.W.2d 246 (1978); Bordas v Detroit General Hospital, 100 Mich App 31, 33 (1980)."
Defendant appealed to the Court of Appeals by leave granted, and that Court affirmed. Howard, supra.
The panel first addressed defendant's sufficiency of the evidence claim. The Court reviewed the expert testimony and found it "sufficient to sustain the WCAB's findings of fact." Id., p. 645, 348 N.W.2d 286. As to defendant's argument that it was the plaintiff's heart disease that prevented his continued employment, the Court held that
"an independent, intervening event resulting in a new disabling medical problem does not alone justify the denial of benefits for a continuing work-related injury. Powell v Casco Nelmor Corp, 406 Mich 332, 354-355; 279 NW2d 769 (1979)."
The panel also rejected defendant's argument that benefits should have been denied on the basis of plaintiff's inconsistent representations to his insurer in 1963.
Regarding application of the two-year-back rule, the Court applied the rule of Kingery, supra, and Kleinschrodt, supra, and upheld the WCAB's decision. The Court reasoned that
"the WCAB is not required to consider issues raised for the first time before it. On the facts of this case, where the record is devoid of any compelling explanation for defendant's failure to raise the applicability of the two-year-back rule before the hearing officer, we find no abuse...
