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Performance on cognitive inhibition has been reported to decline in older adults, as they had a lower ability to indicate the color of words while ignoring the meaning of the word compared to young adults ( Scarpina and Tagini, 2017 Rey-Mermet and Gade, 2018 Gajewski et al., 2020). Cognitive inhibition is the ability to inhibit ongoing irrelevant information while executing actions to achieve a specific goal. The effect of increasing age on executive function has been extensively studied for 3 subdomains: cognitive inhibition, cognitive flexibility, and working memory. A decline in these functions results in impairment of instrumental activities of daily living (IADL) function among older adults ( Jefferson et al., 2006). Executive function (EF) and perceptual-motor function (PMF) are the other components of cognitive function that involve the ability of a person to organize, manage, and execute activities in daily living ( Sachdev et al., 2014). A decline in cognitive processing speed was reported in middle adults when the speed of matching symbols with numbers ( Zimprich and Mascherek, 2010) and counting numbers was used to assess this cognitive function ( Ferreira et al., 2017). Language and episodic memory generally remain intact until the age of 80 y, while processing speed declines with increasing age and rapidly declines after 60 y ( Anstey and Low, 2004 Salthouse, 2010). Advanced age is an important factor leading to the decline of several neurocognitive functions, but the rate of cognitive decline and the extent of cognitive change vary among different neurocognitive domains ( Hughes et al., 2018). The decline of neurocognitive function varies among persons, ranging from a minor problem such as subjective memory complaints to a major problem such as dementia, which affects the ability to make an important decision, perform daily activities and live independently ( Sachdev et al., 2014). Neurocognitive functions are essential for a person to work and perform activities of daily living independently. Cognitive flexibility was the only MCI-sensitive cognitive function. In conclusion, cognitive inhibition decreased earlier in middle adults, whereas EF and PMF started to decline in older adults. To control the confounding effect of education level, the results showed that only cognitive flexibility was further decreased in older adults with probable MCI compared to those without MCI ( pā<ā0.05). For the age difference, working memory, cognitive flexibility, visual perception, and visuoconstructional reasoning remained stable across middle adults and started to decline in older adults, while cognitive inhibition began to decrease in middle adults and it further declined in older adults. Group differences were found for all subdomains of EF and PMF ( pā<ā0.05), except for perceptual-motor coordination, indicating that this subdomain could be maintained in older adults and was not affected by MCI. The PMF, visual perception, visuoconstructional reasoning, and perceptual-motor coordination were evaluated using the clock reading test, stick design test, and stick catching test, respectively. The EF, working memory, inhibition, and cognitive flexibility were evaluated using digit span backward tasks, the Stroop color-word test, and the modified switching verbal fluency test, respectively. The EF and PMF were investigated across four groups of 240 participants, 60 in each group, including early adult, middle adult, older adult, and older adult with probable MCI. This study aimed to determine age-related and MCI-related cognitive impairments of the EF and PMF. It is unclear whether the decline in executive function (EF) and perceptual-motor function (PMF) found in older adults with mild cognitive impairment (MCI) is the result of a normal aging process or due to MCI. Department of Physical Therapy, Faculty of Physical Therapy, Srinakharinwirot University, Nakhon Nayok, Thailand.Yupaporn Rattanavichit Nithinun Chaikeeree Rumpa Boonsinsukh Kasima Kitiyanant *