Alzheimer's disease and co-morbidity: increased prevalence and possible risk factors of excess mortality in a naturalistic 7-year follow-up.

BACKGROUND: Subjects with late-onset Alzheimer's disease (AD) have to be sufficiently healthy to live long enough to experience and to be diagnosed with dementia in later life. In contrast, neurodegeneration and cognitive deficits in AD may increase the frequency of co-morbid disorders and their possible influence on mortality. Consequently, we investigated whether the pattern of co-morbidity and its relevance for later death differed between hospitalized AD and age-matched controls subjects.

METHODS: Co-morbid diseases with a prevalence of more than 1% at hospital admission were compared between 634 hospitalized AD and 72,244 control subjects aged above 70 years admitted to the University of Birmingham NHS Trust between 1 January 2000 to 31 December 2007. Risk factors, i.e. co-morbid diseases that were predictors of mortality within the 7-year follow-up, were identified and compared.

RESULTS: Subjects with AD suffer more eating disorders, infections, brain diseases and neck of femur fractures than other hospitalized elderly patients. In contrast, some cardiovascular diseases and diabetes mellitus were less prevalent in AD subjects in comparison with hospitalized controls. Diseases that might have contributed to later mortality in AD were pneumonia, ischemic heart disease and gastroenteritis, but there were no significant differences in their impact on mortality compared to other hospitalized elderly subjects with the same co-morbidities in multivariate logistic regression analyses.

CONCLUSION: Patients with AD have a different pattern of co-morbidity, but die from the same diseases as other hospitalized patients. Infections including pneumonia and diseases that may occur secondary to neurodegeneration and cognitive decline may need special attention in patients with AD who may not be able to identify or report the early symptoms. Preventive measures may be helpful to reduce the high risk and fatal consequences of undetected disease in AD.