Does Schizophrenia in Offspring Increase the Risk of Developing Alzheimer's Dementia

Abstract

Background/Aims: Prior studies have consistently found a higher risk of dementia in individuals with schizophrenia, but whether this is due to a common etiology between the disorders remains obscure. We wanted to elucidate this association by investigating whether schizophrenia in offspring increases the risk of Alzheimer's dementia. Methods: All individuals born between 1930 and 1953 were identified through national registers and followed from their 50th birthday until the date of Alzheimer's dementia, death or end of the study. Regressions were performed to evaluate the association between offspring with schizophrenia and Alzheimer's dementia. Results: Individuals with offspring with schizophrenia did not have an increased risk of Alzheimer's dementia [incidence rate ratio (IRR), 0.97; 95% CI, 0.88-1.07] compared to individuals with offspring without psychiatric contact. This finding remained stable when evaluating early-onset (IRR, 1.10; 95% CI, 0.91-1.31) and late-onset Alzheimer's dementia (IRR, 0.92; 95% CI, 0.88-1.07). Similar findings were made for vascular and unspecified dementia. Conclusion: The finding of no familial coaggregation between schizophrenia and Alzheimer's dementia may suggest that no common etiology between the disorders exists. This may indicate that the excess risk of dementia in individuals with schizophrenia is a by-product of the higher rates of somatic comorbidity and adverse health risk factors among these individuals.

Schizophrenia and risk of dementia: a meta-analysis study

“…In total, 32 studies were excluded: 25 lacked necessary data, 10 – 14 , 16 – 20 , 32 – 46 one was a review, 47 five did not report dementia outcome, 21 – 25 and one was a sample duplication. 15 Finally, there were six papers including 206,694 cases of dementia and 5,063,316 participants in the meta-analysis 48 – 53 ( Figure 1 ).…”

“… 71 Moreover, there is evidence that the excess risk of dementia in subjects with schizophrenia may be explained by adverse health risk factors. 15 Thus, there are many potential reasons why people with schizophrenia may have progressive cognitive impairment during the course of the disease. 19 …”

“…Some studies have made an effort to evaluate the hypothesis of a shared etiology between schizophrenia and dementia by using mental disorders as determining predispositions for dementia. 15 Longitudinal studies have confirmed the relationship between schizophrenia and dementia risk. 16 – 18 A number of studies have found a significant cognitive decline over time in people with schizophrenia.…”

Familial Co-Aggregation of Dementia with Schizophrenia: A Cross Sectional Pedigree Analysis

“…Several studies have addressed the familial coaggregation of the two disorders and have yielded incongruent results. [11][12][13][14][15] Narayanaswamy et al 16 reported significantly higher morbid risk for psychosis in early-onset dementia (EOAD) proband families and proposed a possibility of genetic overlap between dementia and psychosis. Thereby, in continuation of the proposal, there is a definite need to study the familial loading of dementia in families of patients with schizophrenia, to establish familial coaggregation.…”

“…This is in convergence to a recent population-based study which reported that schizophrenia proband families did not have an increased risk of Alzheimer's [incidence rate ratio (IRR), 0.97; 95% CI, 0.88-1.07], vascular, or unspecified dementia. 15 Rohde et al, 15 in turn, postulated that there might be no common etiological basis between the two disorders and that the associations detected between the two in previous studies might [11][12][13][14][15] be false because of higher rates of somatic comorbidity (like DM) among these individuals. But despite the increased proportion of somatic morbidity (like DM in schizophrenia probands families) in our study, there was nonreporting of MNCD.…”