Interestingly, odor identification was also related to AD risk and change in cognitive function, consistent with prior research [196,197], and with decline in motor function suggesting that this too might have a common causation. This was supported by the clinical pathologic analyses which find that measures of AD pathology were related to olfactory function, parkinsonian signs, frailty, and strength. Lewy bodies were also related to odor identification and parkinsonian signs. Given that it is highly unlikely that parkinsonian signs, frailty, strength and odor identification cause the accumulation of neuropathology, it is likely the case that neuropathology leads to parkinsonian signs, frailty, loss of strength, and impaired odor identification. Thus, changes in motor function and odor identification may be early signs of AD pathology and may appear prior to the development of not only clinical AD but also prior to the onset of MCI.
