The association between frailty and vascular dementia

Frailty is a clinically recognized syndrome that results from an age-associated decline in reserve and function across multiple physiological systems.1 There are two commonly used clinical definitions. The Rookwood definition (1994)2 is essentially a Cumulative Burden Index which includes health conditions and deficits (therefore embracing cognitive impairment). The Fried definition (2001) proposes that frailty definition is met if the person has at least 3 of the following criteria: 1) low grip strength 2) low energy 3) slowed walking speed 4) low physical activity and 5) unintentional weight loss.3 It is associated with increased risk for falls, decreased mobility, mortality and institutionalisation.4 Data from the Chinese longitudinal healthy longevity survey, the largest nationally representative sample of older adults in China, has concluded that higher levels of frailty significantly increase relative risk ratios of mortality for all types of death.5 Another syndrome of which increasing incidence occurs with increasing age, is dementia. Eight million and four hundred thousand, or 4.6% of the population aged 60 and over in mainland China, Hong Kong and Taiwan, live with dementia.6 Of great interest is the relationship between dementia and frailty, two syndromes that show increasing incidence with increasing age. Numerous epidemiological studies have reported an association between frailty and dementia. In these studies, vascular dementia (VaD) has been the most significant form of dementia associated with frailty while the association between frailty and Alzheimer’s disease is less certain, with mixed results ranging from an association to no association.7 VaD is the second most common form of dementia and in some parts of Asia, including some part of China,8 is the most common form of dementia, hence it is of special interest to examine its relationship with frailty. This paper will aim to examine the current literature investigating the association between VaD and frailty, postulate plausible mechanisms for this association, and identify implications for not only clinical practice, but future research