In what may be among the longest-running and widest-ranging cases of academic fraud, one of the most prolific researchers in anesthesiology fabricated much of the data underlying his research, said a spokeswoman for the hospital where he works.

The researcher, Dr. Scott S. Reuben, an anesthesiologist in Springfield, Mass., who practiced at Baystate Medical Center, fabricated data in some or all of the 21 journal articles dating from at least 1996, said Jane Albert, a spokeswoman for Baystate Health.

The reliability of dozens more articles he wrote is uncertain, and the common practice — supported by his studies — of giving patients aspirinlike drugs and neuropathic pain medicines after surgery instead of narcotics is now being questioned.

Paul Cirel, a lawyer for Dr. Reuben, said that he could not discuss the case because Baystate had investigated it as part of a confidential peer-review process. Baystate officials “were aware of extenuating circumstances,” Mr. Cirel said.