Activity patterns are associated with fractional lifespan, memory, and gait speed in aged dogs

Abstract

Maintaining an active lifestyle is considered a hallmark of successful aging. Physical activity significantly reduces the risk of cognitive decline and Alzheimer's disease in humans. However, pain and lack of motivation are important barriers to exercise. Dogs are a remarkable model for translational studies in aging and cognition as they are prone to Canine Cognitive Dysfunction syndrome, which has many similarities with Alzheimer's disease. According to owner reports, changes in activity levels are characteristic of this syndrome, with decreased daytime activity, but also excessive pacing, especially at sleep time. We used physical activity monitors to record the activity of 27 senior dogs and evaluated the association between activity level and age, fractional lifespan, cognitive status measured by an owner questionnaire and cognitive tests. We also assessed the relationship between activity and joint/spinal pain, and the off/on leash gait speed ratio (a potential marker of gait speed reserve and motivation). We found that activity patterns in dogs are associated with fractional lifespan and working memory. Additionally, dogs with higher on/off leash gait speed are more active in the afternoon of weekdays. These results encourage future studies evaluating how physical activity can improve or delay cognitive impairment in senior dogs.

Figure 1

Relationship between age (a,b) and fraction of lifespan (c,d) on activity levels in senior dogs. For each figure, the upper graph illustrates activity over time for different levels of the variables analyzed and the lower graph indicates the level of significance of the differences. When the observed statistic (red line) is above the test of significance set at 0.05 (blue lines) it indicates significant differences between different levels of the variable. The dashed and the dotted lines indicate global and point-wise test of significance respectively. Older dogs showed lower activity levels between 5.00 and 8.00 PM on weekdays and between 2 to 5 PM on weekends. Also, during weekend nights, older dogs were more active around 5 AM.

Figure 2

Relationship between CADES and activity levels in senior dogs on weekdays (a) and weekends (b). The upper graph illustrates activity over time for different levels of the variables analyzed and the lower graph indicates the level of significance of the differences. When the observed statistic (red line) is above the test of significance set at 0.05 (blue lines) it indicates significant differences between different levels of the variable. The dashed and the dotted lines indicate global and point-wise test of significance respectively. Dogs with higher CADES scores were more active between 3 to 5 AM during both weekdays (a) and weekends (b) and less active around 1 AM.

Figure 3

Relationship between performance on cognitive testing and activity levels in senior dogs on weekdays (a,c,e,g) and weekends (b,d,f,h). The upper graph illustrates activity over time for different levels of the variables analyzed and the lower graph indicates the level of significance of the differences. When the observed statistic (red line) is above the test of significance set at 0.05 (blue lines) it indicates significant differences between different levels of the variable. The dashed and the dotted lines indicate global and point-wise test of significance respectively. No relationship was observed with performance at sustained gaze (a,b). Dogs with higher scores in memory tasks were more active in the evening during weekdays (c) and weekend (d). On weekends they were also more active between 12 and 2.45 AM and less active between 3.45 and 5.30 AM. On weekdays, dogs with better performance also showed a reduction in activity levels between 9 and 10.15, but this did not surpass the global significance. Performance on the cylinder tasks, considered tests of executive function, was less clearly associated with activity levels (e,g). Differences were most notable at the weekend when dogs are more active, but non achieved global significance.

Figure 4

Relationship between joint (a,b) and spinal pain (c,d) on activity levels in senior dogs. The upper graph illustrates activity over time for different levels of the variables analyzed and the lower graph indicates the level of significance of the differences. When the observed statistic (red line) is above the test of significance set at 0.05 (blue lines) it indicates significant differences between different levels of the variable. The dashed and the dotted lines indicate global and point-wise test of significance respectively. Dogs with greater joint pain were more active between 4.15 and 5 AM during the weekend (b) but not during weekdays (a). Dogs with higher spinal pain were less active in the evening between 5.30 and 7.15 PM during weekdays (c) but not during the weekend (d).

Figure 5

Relationship between off leash to on leash gait speed and activity levels in senior dogs during weekdays (a) and weekend (b). The upper graph illustrates activity over time for different levels of the variables analyzed and the lower graph indicates the level of significance of the differences. When the observed statistic (red line) is above the test of significance set at 0.05 (blue lines) it indicates significant differences between different levels of the variable. The dashed and the dotted lines indicate global and point-wise test of significance respectively. Dogs with higher levels of food-motivation were more active between 10.30 to 2.15 PM on weekdays.