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Editorial: no health without cognitive health

DOI:10.1097/YCO.0000000000000305 The WHO adopted a definition of health in 1946 as ‘a state of complete physical, mental and social wellbeing and not merely the absence of disease or infirmity’ [1]. This definition had a major impact on the conceptualization of health as a state of positive well-being that referred to the whole person in a social context. Although the focus in the early years was on physical health, the last 3 decades have seen an increasing emphasis on mental health in which ‘every individual realizes his or her own potential, can cope with the normal stresses of life, can work productively and fruitfully, and is able to make a contribution to her or his community’ [2]. What is not usually emphasized in this definition is the importance of healthy cognition. Cognition, which originates from the Latin verb cognosco (‘to know’), refers to mental processes such as attention, memory, knowledge, reasoning, computation, decision-making, judgement, language function, perception, visuospatial abilities, and aspect of social interaction (social cognition). Psychologists distinguish it from emotion and behaviour (conation), although all are dependent on brain processes that are often seamless. As with other aspects of health, cognition varies from individual to individual, and with age, and a host of other factors. Good cognition is critical for optimal functioning at work, in the family and the community. As mental health usually has a focus on normality of emotion and behaviour, it is appropriate to place a separate emphasis on cognition, and state that there is ‘no health without cognitive health’. The state of cognitive health of the world has been brought under sharp focus by the epidemic of dementia. It is estimated that there were 46.8 million individuals with dementia in the world in 2015, and this number is expected to double in 20 years [3]. The greatest rise is likely to occur in low and middle-income countries. Dementia care has been estimated to cost nearly $1 trillion, with this figure projected to double by 2030 [3]. The cost does not fully capture the informal burden of dementia on the affected persons and their family and supporters [4]. Furthermore, in addition to dementia, there are a large number of individuals with mild cognitive impairment (MCI) who have more subtle impairment owing to varying levels of cognitive