Relationship Between Heart and Brain: A New Piece of The Puzzle

This article refers to ‘Cognitive performance in late adolescence and long-term risk of early heart failure in Swedish men’ by M. Lindgren et al., published in this issue on pages xxx. In this issue of the Journal, Lindgren and colleagues followed a cohort of over one million Swedish men from their late adolescence.1 They were enrolled in mandatory military conscription, during which they underwent a series of cognitive tests that examined their logical, verbal, visuospatial and technical ability. Lindgren et al. estimated the association of the performance in cognitive tests with the risk of incident heart failure (HF), using data from the Swedish Hospital Discharge Register. This study demonstrated that low cognitive performance in late adolescence was associated with an increased risk of HF and that the risk was greatest for men with the lowest level of cognitive functions.1 These results are well in line with a large body of evidence on the relationship between early-life cognitive skills and the development of cardiovascular disease,2 but novel in the HF literature. Interestingly, the study participants were on average as young as middle-aged at the time of their first hospitalization for HF. This is of interest because the burden of HF is increasing in some subgroups of young people and therefore the strategies to prevent HF would likely have the greatest impact if applied early in life.3 In the context of demographically aging populations, this article may also help us to better understand the relationship of the frequently co-occurring HF and cognitive impairment in the old age.4-7 Previous studies found that HF is associated with a damage in brain areas that could contribute to cognitive deficits, development of cognitive impairment as well as dementia including Alzheimer's disease.8-11 Worse cognitive function was observed already at early stages of left ventricular dysfunction and furthermore, even in younger people without cardiovascular disease, there was an association between subclinical cardiac dysfunction and subtle injury of the brain.3, 12 Two main theories emerged, explaining mechanisms of this complex relationship.4, 5 First, cognitive impairment and HF could be both results of the synergistic functioning of common risk factors, such as hypertension, diabetes or obesity, and similar pathophysiologic processes.4 Second, cognitive impairment may be a consequence of HF, resulting from hypoperfusion and/or micro-embolism.4, 5, 13, 14 These two theoretical frameworks implied that prevention of HF is good for brain health, and correct management of cardiovascular health could have a benefit for patients with cognitive impairment.4, 5, 15 However, the study of Lindgren et al. reminds us that the relationship between HF and cognition is bi-directional and lower cognitive functions may actually precede HF. This adds an additional piece into the understanding of the complex interplay between social and biological mechanisms that emerge across the lifespan and may result in HF and cognitive impairment. Cognitive performance before the onset of HF or cardiac dysfunction has not been taken into account in previous studies of the heart–brain axis.3-5, 8-11 Is it of interest for future studies to which extent the association of HF and cognitive impairment would persist, if the previous level of cognition was accounted for. This study shifts the focus back towards the early life and emphasizes an unused opportunity of primary prevention of HF. Preventative strategies, particularly those focusing on nutrition, physical activity, reduction of blood pressure and obesity, should be targeted early in life and be tailored according to intellectual performance. People with lower intelligence scores would likely benefit the most from preventative interventions. Furthermore, future studies should disentangle early-life material, biological and psychosocial antecedent of low cognitive performance in late adolescence. This knowledge could indicate how to break the chains of adverse events or mitigate some of their effects in order to prevent HF. Conflict of interest: none declared.