Objective Over several years, one of the authors observed what appeared to be a relationship between a decrease in total lung capacity (TLC) and insulindependent diabetes mellitus (IDDM) in patients who were candidates for kidney transplantation.

Research Design and Methods In an effort to define this potential relationship, pulmonary function tests (PFTs) were reviewed on all available kidney transplant candidates between 1983 and 1986. The patients were divided into two groups—those with kidney failure caused by IDDM (group 1) and those with kidney failure from other causes (group 2). A third group (control subjects) of volunteers with IDDM but without evidence of kidney failure was evaluated by PFTs in an attempt to determine whether IDDM without kidney failure was also associated with a decrease in TLC.

Results Demographics of the two groups with kidney failure were similar. However, the duration of IDDM in the volunteers with IDDM was significantly shorter than in group 1 patients (19.6 vs. 25.9 yr). The TLC of group 1 patients was significantly smaller than the TLC of both the group 2 patients and the volunteers with IDDM.

Conclusions We believe that these data suggest that the association between IDDM and decreased TLC is the result of IDDM and not kidney failure. Because our volunteers with IDDM were significantly younger than the patients with IDDM and kidney failure, we can draw no conclusions about any separate contribution of kidney failure to changes in TLC in people with IDDM.