Mild cognitive impairment (MCI) is characterized by cognitive decline beyond what is expected for one's age and education level without considerable interference with daily functioning.1 It is considered an intermediate phase between normal cognition and dementia. In Taiwan, the MCI prevalence among older adults aged ≥65 years is 18.76 %,2 with a higher prevalence in rural areas than in urban areas (25.1% vs 10.8 %).3 The older adult population with MCI experiences a notable decline in mobility performance. Declines in gait speed occur across the cognitive spectrum, from cognitively healthy individuals to those with subjective cognitive decline, MCI, or dementia, in older adults.4 Older individuals with MCI demonstrate reduced lower-limb muscle strength and balance.4 Individuals with MCI exhibited poorer performance in gait speed and on the Short Physical Performance Battery (SPPB) than did those without MCI.5

The SPPB is a widely employed performance-based tool designed to assess overall physical function in community-dwelling older adults.6, 7, 8 The SPPB encompasses 3 key components: the standing balance, 4-m walk, and 5-times chair stand tests. Each component of the SPPB is scored on a scale of 0 to 4, with the total score ranging from 0 to 12. Higher scores indicate better physical function. The total scores are categorized as follows: 0 to 3 indicates severe mobility impairment, 4 to 6 indicates moderate mobility impairment, 7 to 9 indicates mild mobility impairment, and 10 to 12 indicate little to no mobility impairment.9 The SPPB scores serve as valuable indicators for screening frail or prefrail older adults. A total score of ≤9 points or ≤11 points may indicate frailty or prefrailty. Moreover, specific cutoff points for walking time and chair stand time for frailty were identified: ≤5 s for walking time and ≤13 s for chair stand time. For prefrailty screening, the cutoff points are ≤4 s for walking time and ≤10 s for chair stand time.10 In summary, the SPPB could provide meaningful gradations of functional status in older adults.

A review article that synthesized 10 studies indicated that the SPPB demonstrated good to excellent reliability in assessing community-dwelling older adults, with intraclass correlation coefficients (ICCs) ranging from 0.81 to 0.97.11 However, the majority of these studies were conducted in European and American countries, with only one study having adequate (≥100) sample sizes. The test-retest reliability of the SPPB among older people with cognitive impairment has rarely been examined. Studies in this domain have predominantly focused on dementia.12, 13, 14 The limited information on the SPPB's test-retest reliability and minimal detectable change (MDC) among individuals with MCI can prevent accurate interpretation of scores and negatively affect the practical utility of the SPPB in this population.

Test-retest reliability represents the reproducibility of repeated trials of a measure or the absence of random errors which should be considered prior to application in research and clinical practice.15 Moreover, providing researchers and clinicians with MDC values can assist with determining whether a patient's change score is beyond random measurement error.16 The current study aimed to investigate the test-retest reliability and MDC of the SPPB in older adults with MCI. Additionally, the test-retest reliability and MDC for specific components of the SPPB, namely walking time and chair stand time, were investigated.