Background: Cardiovascular risk factors play an important role in the development of cognitive impairment and dementia. The American Heart Association (AHA) has defined a metric of optimal cardiovascular health, known as the Life’s Simple 7 (LS7) score. LS7 is composed of four health behaviours (smoking, diet, physical activity, and body mass index (BMI)) and three biological health factors (plasma glucose, total serum cholesterol, and blood pressure). The aim of this dissertation was to investigate the associations between cardiovascular health, assessed with LS7, and cognitive decline (I) in young-old and old-old individuals and (II) in the preclinical stage of neurodegenerative dementia. Furthermore, we aimed to (III) monitor changes in LS7 and relate them to changes in cognition.
Methods: Participants were from the population-based Swedish National Study on Aging and Care in Kungsholmen (SNAC-K). Study I included 1,950 individuals, Study II included 1,449, and Study III included 1,022 participants. Over a follow-up period of up to 15 years, five cognitive domains were assessed: episodic memory, semantic memory, verbal fluency, perceptual speed, and global cognition. Preclinical dementia was defined as being dementia-free at baseline and diagnosed with dementia 3, 6, 9, or 12 years later. The LS7 score was calculated for baseline and for the 6-year follow-up. Linear mixed models were used to explore the associations between LS7, cognitive decline, and dementia status.
Results: In Study I, better LS7 was associated with better cognitive performance and slower cognitive decline in the young-old (< 78 years) group. Better results for smoking, plasma glucose, and BMI were associated with faster cognitive decline in old-old individuals (⡥ 78 years), possibly as a consequence of an impending dementia disorder. In Study II, better cardiovascular health in young-old individuals was associated with a slower cognitive decline in the preclinical stage of neurodegenerative dementia, driven primarily by diet and plasma glucose. In study III, worsening of LS7 was clearly associated with faster decline in the old-old, while improvement tended to be associated with faster cognitive decline in the young-old group.
Conclusions: Our findings demonstrate the intricate relationship between cardiovascular risk factors and cognitive decline in old age, underscoring the importance of age in the strength of these associations. Furthermore, the results support the significance of maintaining good cardiovascular health, even in very old age and during the preclinical phase of neurodegenerative dementia.
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