Dr. Maude Wagner is a Postdoctoral Research Fellow in Biostatistics, with expertise in longitudinal modeling applied to cognitive ageing at the Rush Alzheimer’s Disease Center (RADC) in Chicago. She tweets at @maude_wagner2.
Dr. Francine Grodstein is an epidemiologist, focused on epidemiology of ageing, and Professor of Internal Medicine at the RADC. She was the Scientific Director of the Nurses’ Health Study at Brigham and Women’s Hospital in Boston prior to joining the RADC.
More than 100 years after its discovery, Alzheimer's disease (AD) has become one of the greatest medical and social challenges of our generation. In 2017, the World Health Organization estimated that 47 million older people worldwide are affected by the disease and that a new case of AD is diagnosed every three seconds. The disease dramatically affects families, caregivers, and society at large, with an estimated societal cost of $818 billion (1% of global GDP). Due to the global ageing of populations, and because there is currently no medical breakthrough to prevent or cure AD, the number of people affected by the disease is expected to increase significantly. Thus, it is critical to identify key modifiable preventive factors to preserve brain health, especially episodic memory, which is extremely sensitive with ageing and in the early stages of AD.
Is age-related episodic memory decline inevitable?
Episodic memory (EM) is a memory system that allows conscious recall of past personal events and is essential for participating in meaningful social interactions and accomplish the tasks of daily living. The risk of memory decline increases with age. However, some individuals aged 80 or older have exceptional memory abilities for their age, suggesting that memory loss is not inevitable. Older adults with unusual memory performances have previously been shown to have less brain volume loss and less AD pathology than cognitively average peers of the same age. However, virtually nothing is known about how lifestyle behaviors in early adulthood may contribute to the likelihood of achieving superior cognition in older ages. Using data from 2,730 participants in the US observational prospective Nurses’ Health Study (nurseshealthstudy.org), the authors compared the patterns of lifestyle behaviors, including physical activity and dietary habits, from midlife (52-62 years) through late life (80 years) between women with exceptional EM at age 80 years and cognitively-average controls of the same age and education level.
Two major long-term lifestyle behaviors identified
Compared with cognitively-average controls, women with excellent EM at age 80 had consistently and markedly higher levels of total physical activity from mid- through later-life. The study also suggests that it is not necessary to run marathons to get benefits from activity. Indeed, although smaller, differences between groups remained after accounting for women who engaged exclusively in low-intensity physical activity, including walking and stair climbing. Physical activity was studied in metabolic equivalent tasks (METs)-hours per week, which easily accounts for the frequency and intensity of physical exercise. For example, a value of 12 METs is typically assigned for running, meaning that the body requires 12 times more oxygen (and burns more calories) than when sitting quietly. Energy expenditure in MET-hours per week is the MET values multiplied by the time spent performing it.
Women with excellent EM at age 80 also had consistently greater adherence to the Mediterranean diet since early adulthood than controls. Of note, the Mediterranean diet encourages high intake of healthy compounds, including vegetables (but not potatoes), fruits, legumes, nuts, whole grains, the ratio of monounsaturated to saturated fatty acids, and fish, and limits consumption of red or processed meats and alcohol, which are thought to be harmful to health.
Overall, this study provides evidence that women with high EM ability after age 80 years appear to have had higher levels of physical activity and better diet quality over a longer period of their earlier adult life (and possibly even earlier in life [e.g., childhood]) compared with cognitively-average controls. While needing confirmation in future research, these findings emphasize that early interventions to encourage healthy lifestyle habits should be evaluated for the promotion of optimal cognitive function with ageing.
The full research paper 'Patterns of lifestyle behaviours from mid- through later-life in relation to exceptional episodic memory performance in older women: the Nurses’ Health Study' has been published in Age and Ageing.