A decline in cognitive functioning (which refers to a decline in the performance of mental abilities such as reasoning, planning, remembering, problem-solving, and understanding… as age increases) is common even in individuals without neurodegenerative diseases. Previous studies have identified many factors that are significantly associated with the level of cognitive functioning (e.g. genetics). However, to what extent these contribute to the variation in the level and trajectory of decline in cognitive functioning remains unclear. In a new study published in the journal PLOS ONE, a team of researchers led by Hui Zheng from Ohio University (Ohio, US) analysed data from 7,068 American adults, born between 1931 and 1941, in the 1996–2016 Health and Retirement Study. Researchers collected extensive information on factors (i.e. childhood health, nutrition, education, household wealth, household income, number of marriages, children, chronic diseases, smoking status, physical status, vigorous activity…) that could correlate and contribute to the level of cognitive functioning and the cognitive functioning trajectory from age 54 to 85. The individual factors examined in the study accounted for 38% of the variation between participants in the level of cognitive functioning at age 54. Personal education was the biggest contributor to the population-level variation, followed by race, household wealth, household income, occupation, parental education and level of depression. The contributions of health behaviours (i.e. smoking, obesity and vigorous activity), childhood conditions, chronic diseases, gender, marital status and religion were small (less than 5%). Researchers also found that the variation in cognitive functioning between participants aged 54 was three times as large as the variation in the trajectory of decline in cognitive functioning over the next 30 years. In addition, age only explained 23% of the variation in cognitive functioning progression from age 54 to 85. These findings reveal that more research is needed to identify the factors that determine and contribute to the rate of cognitive decline over age. Understanding why cognitive abilities are better and cognitive decline slower in some people is key to the development of medical treatments that target cognitive functioning.
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0281139