The World Health Organization emphasizes that maintaining functional abilities is essential for the health and well-being of older adults. Among the recommended strategies, regular physical activity is central to the role in preventing diseases and promoting active longevity. However, physical inactivity and sedentary time represent increasing challenges associated with chronic diseases and reduced quality of life. Assessment of physical activity levels is globally examined through self-reported questionnaires, although their accuracy in older adults still generates debate in the literature. In this context, the combination of objective measures, such as accelerometry and self-reporting, can improve the assessment of physical activity levels and support effective strategies for health promotion and prevention.

To evaluate the association and agreement between subjective and objective methods of measuring physical activity in community-dwelling older adults.

In SPSS 20.0, descriptive analysis, frequency distribution of categorical variables, central tendency analysis, dispersion measures of continuous variables, Pearson's Chi-square test and Kappa coefficient were performed. The Active Australia Questionnaire (AAQ) and the International Physical Activity Questionnaire (IPAQ) were used for the subjective assessment of the level of physical activity, and the accelerometer (Actigraph®, Pensacola, Fla, USA; Model GT9X Link; ActiLife Software version 6.11.5) was used for the objective assessment for 7 consecutive days. The Pearson's Chi-square test and Kappa coefficient were performed. Statistical significance set at 5%.

A total of 35 older adults participated in this cross-sectional study. The mean age was (71.06 ± 9.0 years), 23 (65.7%) females and 12 (34.3%) males, IPAQ (Sedentary 0%, Irregularly active 2.9%, Active 60%, Very active 31.1%), AAQ (Sedentary 0%, Insufficiently active 8.6%, Sufficiently active 91.4%), Actigraphy (Sedentary behavior 65.93%, Light activities 15.99%, Moderate and Vigorous physical activity 6.48%). Association - Person's Chi-square: (AAQ: X² = 0.972, P = 0.324), (IPAQ: X² = 6.462, P = 0.040). Agreement - Kappa Coefficient: (AAQ: P = 0.324), (IPAQ: P = 0.451).

The results of this study indicate a significant association between the assessment obtained by the IPAQ questionnaire (short version) and the accelerometry measurement by GT9X, although no agreement was observed between the data. This corroborates previous findings in the literature, which state that, although the subjective measure presents reliability and validity, especially in community studies, compared to the standard of data evaluated through accelerometry, it has a low validity criterion. Therefore, an in-depth assessment of the level of physical activity may indicate preventive measures in the health area. In addition, it is essential to continue investigating the multiple facets of physical activity, considering not only the quantity but also the quality and intensity of the practice.

Although self-reported questionnaires are widely used in community studies and present validation in several situations, they should be used with caution, especially in the older adults.