It has long been a common understanding, that people with intellectual disabilities (ID) ‘are old from the age of 50 years onwards’ (Perkins and Moran, 2010 and Roth et al., 1996). Nevertheless, apart from people with Down syndrome (Roth et al., 1996), premature aging has never been scientifically confirmed for this group. Geriatric frailty occurs early in the population with ID (Evenhuis, Hermans, Hilgenkamp, Bastiaanse, & Echteld, 2012) and is considered to be a risk factor for subsequent deterioration of health and independence (Fried et al., 2001), occurs early in the population with ID. Their mean frailty index scores at age 50–59 years are comparable to those in the general population aged 70–79 years (Schoufour, Mitnitski, Rockwood, Evenhuis, & Echteld, 2013). This early occurrence of frailty might be an explanation for the perceived early aging.
Frailty might be partly caused by multimorbidity, which refers to the occurrence of two or more chronic conditions. The prevalence of multimorbidity has been extensively studied in older people with normal intelligence (Glynn et al., 2011, Schram et al., 2008 and Van Oostrom et al., 2011). The results of these studies imply that prevalence increases with age and is related to female gender, lower education and low social-economic status (Marengoni et al., 2008, Salisbury et al., 2011, Tucker-Seeley et al., 2011 and Uijen and van de Lisdonk, 2008). Despite the numerous studies, treatment options are still vague. Physicians seem to treat each disease separately and show little attention for the synergy between different diseases (Bower et al., 2012), whereas lack of good treatment causes ongoing functional decline, impaired quality of life and early death (Drewes et al., 2011, Fortin et al., 2006, Hunger et al., 2011 and Landi et al., 2010).
People with ID seem to have an increased risk of chronic multimorbidity (McCarron et al., 2013) for several reasons. Multimorbidity may start at a young age, with conditions related to brain damage, impaired brain development, and etiologic syndromes. For example, people with cerebral palsy often have motor impairment, epilepsy and other neurologic problems (Arvio & Sillanpaa, 2003). What is more, risks to develop age-related conditions may be different because of superpositioning on childhood conditions and other unfavorable factors (De Winter, Bastiaanse, Hilgenkamp, Evenhuis, & Echteld, 2012). For instance, an increased risk of cardiovascular risk factors is found both in young and older adults with ID (De Winter et al., 2012, Emerson, 2005 and Haveman et al., 2011). This may not only be attributable to an unhealthy lifestyle, but also to metabolic effects of antipsychotic drug use (De Kuijper et al., 2013) and fragmented sleep–wake rhythms (Maaskant, van de Wouw, van Wijck, Evenhuis, & Echteld, 2013).
Nevertheless, medical care for this group is primarily reactive, i.e. if complaints or observed symptoms are brought to the attention of the physician (Lennox, Diggens, & Ugoni, 1997). Multimorbidity and frail unhealthy life-years may be delayed by treating conditions that are to be expected during early and later adulthood, as well as anticipating healthcare, aimed at prevention and pro-active diagnosis. Consequently, healthcare costs will decrease because of less dependency caused by additional diseases.
To improve healthcare for people with ID, more knowledge on multimorbidity is necessary (McCarron et al., 2013). Therefore, we studied the prevalence and associated factors of chronic multimorbidity in the broad client population, aged 50 years and over, of Dutch intellectual disability service providers. We have also studied the presence of meaningful clusters of multimorbidity, as a basis for anticipating healthcare.
