Use of motor performance tests to differentiate aging effects from disease effects

The present study has demonstrated that behavioral testing can provide non-invasive methods for monitoring the time-courses of aging and disease processes. Performance on two of our tests changed linearly with increasing age in both cardiomyopathic and healthy hamsters, but these changes occured at an earlier age in the CM hamsters than in healthy control hamters. In addition, healthy hamsters showed age-related changes in performance on some tests, while sick CM hamsters did not show parallel changes. These results indicate that disease can modify the rate of change in some markers of aging, and thus they suggest that disease might be able to modify the aging process. However, such a preliminary hypothesis requires much further work. Performance on another behavioral test was shown to be stable throughout much of the lifespan of healthy hamsters, and yet disease in CM hamsters was clearly able to affect it. Thus it was possible to find some tests which discriminated between aging and disease effects, but only because the time-course of the disease we were studying was well defined. Most importantly, these results have suggested a way of thinking about the problem of disease in aging studies that may be more fruitful than others previously used. Examining the changes over time in both healthy subjects (putatively disease-free) and those with disease should allow one to determine which age-related changes are dependent on the presence of organic disease and to separate these from the changes which might inevitably occur solely from increasing age.