Extremity injuries and dementia disproportionately increase the risk for long-term care at older age in an analysis of German Health Insurance routine data for the years 2006 to 2010

Extremity injuries (EI) due to falls [1, 2] are common among older persons [3]. Together with dementia [4], they are important causes of long term care (LTC) [5–8]. In western societies older age groups are growing due to rising life expectancy and large cohorts entering old age. Older people are more likely to experience falls and subsequently incur fractures than younger people [9] and to experience dementia. Increasing EI incidence has also been noted due to increasing fracture incidence independent of age structure, most likely because the number and severity of falls in older populations has increased [10]. In the future, even more people may be expected to experience and live longer with dementia, thus both risk factors might become even more important [11]. EI and dementia will continue to affect LTC need – a field already under considerable strain due to financial and personnel shortages. Not much is known about the combined effects of EI and dementia on LTC, especially in terms of a finer distinction of severe and non-severe injuries of the lower, upper or both extremities. EI and dementia are discrete LTC risks, but can also be causally related and are often present together [12–14].

Maintaining an active and regular social life as well as regularly performing productive tasks decreases the risk of dementia [15], because the associated cognitive stimulation helps preserve cognitive functioning. Lower and upper EI can drastically reduce the ability to uphold social interaction or perform productive tasks at the usual levels and act as a risk factor for dementia in that they reduce cognitive stimulation [16, 17]. Lower EI that limit mobility might be even more influential. Thus, the onset of mobility problems, such as unsteady gait, is recognized as a valid predictor of later cognitive decline [14, 18, 19]. An EI can also indirectly increase the risk for dementia due to a subsequent delirium, which is a risk factor for dementia as well [20].

Conversely, dementia is a pre-existing condition for many fractures, because cognitive deterioration also affects gait and balance, increasing the risk of falling [9, 14, 21, 22]. Dementia thus leads to earlier or more frequent falls and may also increase the severity of fall-related injuries. If present concurrently, the complementary effect of the two central LTC risk factors EI and dementia might further compound the LTC risk. However, the strength of their synergistic effect and to what degree the body region and severity of an EI influence the resulting LTC risk remains unclear.

Our study addresses four topics. First we differentiate between severe and non-severe injuries and hypothesize that Severe EI (SEI) leads to higher LTC risk than Non-Severe EI (NSEI). Second, we distinguish between lower, upper, and both extremities. Lower EI affect movement, upper EI affect manipulation of the environment, and a combination of both might differently affect LTC risk on their own or in conjunction with dementia. Moreover, both kinds of EI may indicate either one drastic injury that affects both extremities or multiple incidents. Third, as limited mobility may reduce cognitive activity and mobility, mobility-limiting lower EI and dementia should increase LTC risk more than upper EI and dementia, with SEI generally causing a higher risk than NSEI. Fourth, we explore the combined effects of dementia and EI on LTC, expecting them to be larger than the individual effect sizes simply added up [23].