suspect dementia? Add walking speed to your checklist – InSight+

It is important to remain mobile in old age in order to remain independent at home and to participate in social and leisure activities in the community. Poor mobility increases the risk of fallingand there is emerging interest in whether its presence may suggest an increased risk of dementia.

Gait and dementia

Dementia is one of the leading causes of disability and death in older Australians† By the time dementia is diagnosed, there is already a significant build-up of pathology in the brain† It is therefore important to identify at-risk individuals early to address modifiable risk factors for dementia prevention and to initiate new treatments as they become available.

It is well known that gait changes occur in the later stages of dementiacontribute to loss of independence and increased risk of falling† However, despite growing evidence, it is less well known that walking speed can slow for many years before being diagnosed with dementia. Further, the combination of slow walking and a subjective cognitive concern increases the risk of dementia to a greater extent than walking slowly alone† However, there is a range of cognitive functions, including memory, language, processing speed and executive functions, and it is not yet known which of these functions are relevant to dementia risk when found with slow gait.

In our new studyusing data from the ASPREE (ASpirin in Reducing Events in the Elderly) Clinical Trial, we examined the utility of different cognitive functions in assessing the risk of future dementia in combination with a decrease in walking speed. We hypothesized that the risk would be greatest in people with gait decline and amnesia, as this combination of measures would reflect the presence of a wide range of brain pathology.

Information and data from 16 855 elderly people from Australia and the US who participated in the ASPREE study contributed to the analysis. ASPREE was a large clinical trial testing the efficacy of low-dose aspirin for the primary prevention of dementia and persistent physical disabilities and for prolonging independent living. The criteria for inclusion were age 70 years or older (or 65 years and older for US participants belonging to minority groups), free of cardiovascular disease, dementia or significant physical disabilities. Cases of dementia were confirmed using validated criteria by an expert panel. Walking speed was measured every 2 years over 3 meters at the usual pace, with cognitive measurements (measures of global cognitive function, delayed memory, processing speed and verbal fluency) taken in the other years.

Four groups were examined for their future risk of dementia:

  • no decline in cognition or gait (reference group);
  • only loss of gait;
  • only cognitive decline, and
  • decline in both gait and cognition (double descenders).

What have we found?

One hundred and seventy-eight participants developed dementia during the study period.

The personal visit schedule was completed by 15 309 participants (median personal follow-up, 4.5 years) and 1546 had incomplete follow-up (median personal follow-up, 2.5 years). Participants with declines in both gait and cognitive function had an increased risk of dementia compared to non-decliners. The risk of dementia was highest in participants with combined gait and memory decline, and averaged in those with gait decline or only cognitive decline. Using repeated measures over multiple time points (ie, tracking decline) was better at predicting risk than single time point measurements.

What do these findings mean?

The findings of this secondary analysis of ASPREE data emphasize the importance of examining gait speed in screening for future dementia risk in older people, and that the combination of slower gait and memory failure may be the most predictive combination.

Interesting is the combination with memory as the best cognitive measure. The DSM IV criteria for a diagnosis of dementia applied in this study required impairment in a non-memory domain in addition to memory impairment† Previous studies have found: slow walking speed is more strongly associated with these non-memory domains, such as executive functions and processing speed† Slowing gait and memory decline can each capture the effects of different brain pathologies.

we know that the majority of people with dementia may have a mixture of pathologies in their brain including the harmful amyloid and tau proteins (strongly related to memory decline) and brain injury from undetected vascular disease (strongly related to gait decline). Therefore, the combination of walking and amnesia is perhaps best to capture the risk associated with these major pathologies affecting a wide variety of brain networks

What should be done in the clinic?

Our findings suggest that serial measurements of a simple test of memory and walking speed may be most useful in clinical screening for future dementia risk in an otherwise healthy elderly person.

Usually only a short cognitive test is used in the clinic to screen for dementia risk and walking is often overlooked. Walking speed can be measured quickly and only requires a measured distance and a stopwatch, so it is attractive for general practice. Measuring walking speed has long been recommended as a measure of an older person’s overall health.

Walking speeds of less than 0.8-1.0 m/s are predictive of adverse outcomes such as falls, disability, hospitalization and mortality (here and here† Therefore, a slow gait speed or a gait deceleration greater than 0.05 m/s per year should trigger a screening of cognition, followed by a more comprehensive assessment if necessary. People considered high-risk may benefit from exercise, a healthy diet, staying socially and intellectually engaged, good blood pressure control, diabetes, and other risk factors that can be modified to prevent dementia.

The ASPREE study was conducted by the School of Public Health and Preventive Medicine, Monash University.

dr. Taya Collyer is a Research Fellow in Biostatistics at Monash University.

Associate Professor Michele Callisaya is a physical therapist with the National Center for Health Aging, Monash University and Peninsula Health. She is also a Principal Research Fellow at the Menzies Institute for Medical Research, University of Tasmania.

The statements or opinions expressed in this article reflect the views of the authors and do not necessarily represent the official policy of the AMA, the MYA or InSight+ unless so stated.

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