A longitudinal study was performed in order to analyze older individuals with and without Parkinson’s Disease and measure their speech breathing and speech production. The older adults were among the ages of 65 and 82. It involved analysis of speech severity, speech production level, utterance length, speech rate, as well as lung volume initiation and termination and their vital capacity. The results showed how with the progression of the Parkinson’s disease, older adults were shown to have a decline in their speech severity, increases with speech production level, an increase in speech rate and no change within utterance length.

M;, H. J. E. D.-W. (n.d.). Longitudinal changes in speech breathing in older adults with and without parkinson’s disease. Seminars in speech and language. Retrieved from https://pubmed.ncbi.nlm.nih.gov/28618443/