Age-related changes in plasma dehydroepiandrosterone levels in adults with Down's syndrome and the risk of dementia.

People with Down's syndrome (DS) are at high risk of developing early onset dementia. Recent studies suggest a link between age-related decreases in dehydroepiandrosterone (DHEA) concentrations and dementia in the general population. The present study investigates the relationship between DHEA serum levels and age and the risk of dementia in adults with DS. The DHEA plasma concentrations of 67 adults with DS and 65 age-matched controls were determined. Participants with DS were assessed for the presence of dementia using the CAMDEX informant interview. The DHEA plasma concentrations decreased with age in subjects with DS as well as in controls. Age significantly predicted DHEA levels in both groups (B = -0.06, t = -4.536, P < 0.001 in the DS group and B = -0.04, t = -2.928, P < 0.005 in control participants). The mean ± SD DHEA level was 3.47 ± 1.41 µmol/l in controls and 2.79 ± 1.24 µmol/l in participants with DS. This difference was significant (t = -2.981, P < 0.01). Within the DS population, ancova revealed a significant relationship between DHEA concentrations and dementia (F(1,65) = 4.348, P < 0.05). We found that DHEA levels declined significantly with age in people with DS and controls and were lower, in comparison to age-matched controls, in people with DS across all ages studied. Those with DS and evidence of dementia have lower DHEA concentrations than those with DS (controlling for age) but without dementia.

The modified CAMDEX informant interview is a valid and reliable tool for use in the diagnosis of dementia in adults with Down's syndrome.

BACKGROUND: Dementia because of Alzheimer's disease (AD) commonly affects older adults with Down's syndrome (DS). Methods are needed, with established concurrent and predictive validity, to facilitate the diagnostic assessment of dementia, when it is complicated by pre-existing intellectual disabilities (ID). We report on the reliability and validity of a modified version of the Cambridge Examination for Mental Disorders of the Elderly (CAMDEX) informant interview, for use when assessing people with DS suspected as having dementia. METHODS: As part of a previous epidemiological study of older people with DS, the CAMDEX informant interview was used to determine the prevalence of dementia. The 74 people with DS included at that time (Time 1) had also completed the Cambridge Cognitive Examination (CAMCOG), the neuropsychological assessment from the CAMDEX schedule. Fifty-six were assessed again 6 years later (Time 2). Based on the CAMDEX informant interview, nine of the 74 at Time 1, and 11 of the 56 at Time 2, were found to meet clinical criteria for AD. Forty-one scored above floor on the CAMCOG at Time 1 and were included in the analysis of cognitive decline. Concurrent validity was established by comparing diagnosis at Time 2 with independent evidence of objective decline on cognitive tasks since Time 1. Predictive validity was established by examining how accurately diagnosis at Time 1 predicted both cognitive decline and future diagnosis. Inter-rater reliability was determined by comparing the level of agreement between two raters. RESULTS: CAMDEX-based diagnosis of AD was shown to be consistent with objectively observed cognitive decline (good concurrent validity) and to be a good predictor of future diagnosis. Although numbers are small, some support is also provided for the accuracy with which diagnosis predicts cognitive decline. Inter-rater reliability was good with Kappa > 0.8 for 91% of items and > 0.6 for all items. CONCLUSIONS: The use of the modified CAMDEX informant interview enables the structured collection of diagnostic information, so that a valid and a reliable diagnosis of dementia can be made in those with pre-existing ID, using established diagnostic criteria.