As people age, their cognitive ability and physical health typically decline. Beyond this age-related decline, however, changes in physical health and cognitive ability are positively related. Indeed, when cognitive ability changes, people also tend to experience changes in physical health. This dynamic relationship may have several explanations.
First, individuals in poor physical health may develop cerebrovascular disease, leading to cognitive decline. Conversely, however, individuals with poor cognitive ability may have trouble practicing health-related behaviors, which worsens their physical health. A third alternative is that poor cognitive ability and physical health may affect each other.
Prior studies that examined the temporal ordering of the relationship between cognitive ability and physical health have derived support for all three temporal orderings. Thus, it was unclear whether changes in cognitive ability or physical health preceded change in the other.
In a study published in Psychology and Agingopens in new window, Nelson, Jacobucci, Grimm, and Zelinski explicitly tested (a) whether memory predicted change in physical health 2 years later, (b) whether physical health predicted change in memory 2 years later, and (c) whether both memory and physical health predicted changes in each other 2 years later. To unify the disparate findings from prior studies, the authors tested these research questions in 9,103 individuals aged 50–87 from the Health and Retirement Study, a nationally representative sample of the U.S. population, and measured memory and physical health broadly.
The authors found that better memory at a given time point predicted less decline in physical health 2 years later. Although there was also evidence that physical health predicted changes in memory 2 years later, this effect was much weaker and thus less meaningful. Finally, the effect of memory on change in physical health was much stronger in individuals aged 75–87 than those aged 50–74.
Thus, better memory protected against decline in physical health, and this effect was particularly strong in older individuals. Several health-related behaviors may explain memory’s buffering effect on physical health. For instance, individuals with poor memory may have trouble adhering to medication schedules. This might immediately affect physical health, especially in older adults who often depend on complex medication schedules.
Although physical health did not meaningfully predict memory, this does not mean physical health has no effect on memory. Instead, poor physical health may lead to cognitive decline due to gradual wear and tear on the cerebrovascular system. This would likely take several years to occur, making the 2-year time intervals too short to capture this process. These causal mechanisms remain to be tested, but both may drive the dynamic relationship between memory and physical health.
In sum, better memory protects against decline in physical health. This finding highlights exciting opportunities for future research into the causal mechanisms and perhaps eventual intervention in this relationship.
Note: This article is in the Developmental Psychology topic area. View more articles in the Developmental Psychology topic area.