A new analysis examines relative statistical relationships between various life factors and cognitive decline in older Americans, highlighting gaps in knowledge needed to mitigate cognitive decline. Hui Zheng of Ohio State University, USA, and colleagues present these findings in the open access journal PLOS ONE on February 8, 2023.

Millions of older Americans are experiencing cognitive decline. However, only about 41 percent of this decline can be statistically explained by dementia – abnormal decline caused by conditions such as Alzheimer’s disease, cerebrovascular disease and Lewy body disease. Prior research has identified many other factors that may also contribute to cognitive decline, from genetics to early life nutrition, but their relative impact remains unclear.

To shed new light, Zheng and colleagues analyzed data from 7,068 American adults born between 1931 and 1941 who were part of a larger study – the Health and Retirement Study – that regularly measured their cognitive function from 1996 to 2016. The study also collected extensive information on personal factors that could contribute to cognitive decline, such as socioeconomic factors, physical health measures and behaviors, including exercise and smoking.

Together, the many factors considered in the study were statistically responsible for 38 percent of the variation between participants in their level of cognitive functioning at age 54. parental education made the largest statistical contribution to that population-level variation, with early life conditions and adult behaviors and illnesses contributing less.

However, all factors considered accounted for only 5.6 percent of the variation in how participants’ cognitive function changed with age.

Unlike many previous studies, this study also distinguished between age-related cognitive decline and cognitive decline unrelated to aging. Age accounted for 23 percent of the variation in how cognitive function changed from age 54 to 85, but the remaining 77 percent could not be explained statistically due to the many factors taken into account.

These findings suggest that more research is needed to identify key factors contributing to the rate of cognitive decline, which could help inform medical treatments, policies, and equity-based strategies to slow decline.

Hui Zheng adds: “Socioeconomic conditions in adulthood play a predominant role in shaping levels of cognitive functioning. Future research is urgently needed to discover key determinants of the slope of decline to slow the progression of cognitive impairment and dementia.”

Adds Kathleen Cagney: “Understanding cognitive health and cognitive decline is paramount. We need to look at the long term, with attention to the timing and nature of life experiences, if we want to gain fundamental insights that can inform care and treatment.”

Magazine reference:

  1. Zheng H, Cagney K, Choi Y (2023) Predictors of cognitive functioning trajectories in older Americans: a new study of 20 years of age- and non-age-related cognitive change. PLoS ONE 18(2): e0281139. DOI: 10.1371/journal.pone.0281139