Accurately assessing physical activity levels in older adults has been a challenge for health professionals and researchers. Not only are self-reports of physical activity subject to recall bias, but in the case of older adults, the accuracy of self-reports can be complicated by cognitive impairment or a fear of losing independence. However, physicians and researchers are now using medical-grade accelerometers similar to those used in activity trackers to get more direct measures of individuals’ activity levels. Recently, researchers examined the extent to which measurements from wrist accelerometers worn by older adults were associated with difficulty performing activities of daily living (ADLs) and instrumental activities of daily living (IADLs). They also examined whether the accelerometers contributed additional information about disability beyond what is reported on a typical questionnaire about older adults’ activity. Despite the growing availability of wrist accelerometers, it had not been demonstrated that this type of accelerometer’s measurements could be reliably associated with disability in older adults.
This study involved 738 participants aged 62 to 91 in the nationally representative National Social Life, Health and Aging Project. The mean age of these participants was 72. These participants wore wrist accelerometers continuously for 72 hours. These trackers recorded the participants’ activity levels (in the form of acceleration/deceleration data) every 15 seconds for the duration of this period. This data was calculated into routine activity time (a sum of the periods during which motion was recorded) and immobile time (which underestimates sedentary time, since some sedentary time will involve wrist and arm motions). In addition, participants were asked about their ability to perform seven ADL and seven IADL tasks. The participants were also asked to give a report of their average amount of vigorous physical activity over the past 12 months.
Looking at the relationship of the accelerometer data and ability to perform ADLs, less routine activity time recorded was significantly associated with difficulty performing all ADLs except transferring in and out of bed, and with five of the IADLs, such as light housework, shopping, and meal preparation. Each increase of 10 points in routine time corresponded with a decreased risk of reporting a disability. For example, for each 10 point increase in routine activity, there was a 15 percent decreased risk of a participant reporting difficulty walking one block. Similarly, the immobile time data showed that more time spent without moving was associated with difficulty performing five ADLs and five IADLs. For example, a 10% increase in immobile time while awake was associated with a 55 percent increase in risk of reporting difficulty walking across the room. Additionally, low amounts of self-reported vigorous activity was also related to difficulty performing all ADLs and five IADLs.
Importantly, the researchers also asked whether wrist accelerometers were capturing aspects of activity patterns associated with risks that aren’t also captured by asking about self-reported physical activity. In comparing the accelerometer data to self-reported levels of physical activity, the researchers concluded that both were predictors of a number of ADL and IADL outcomes, with independent and additive effects in the accurate prediction of disability. They conclude that “measuring only self-reported vigorous PA [physical activity] frequency may not adequately identify all activity risk factors, leading to missed opportunities to intervene. Missing these health risks/benefits is of particular public health importance for seniors who spend more of their time in routine and sedentary activity, and are most likely to realize benefits from increasing light activity and reducing sedentary activity.”
The researchers concluded that wrist accelerometer technology shows promise for helping diagnose disability risks as well as for helping health professionals work with individuals to set individualized physical activity targets. It remains to be determined whether inexpensive, commercially available accelerometers offer the degree of accuracy necessary to show the relationship between wrist accelerometer data and disability, but this study does demonstrate the clinical functionality that this technology can offer older adults.
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