Knopman, David S.

ABSTRACTBACKGROUND AND PURPOSEMild cognitive impairment (MCI) precedes both Alzheimer's disease (AD) dementia and with Lewy bodies (DLB). We investigated proton magnetic resonance spectroscopy (MRS) characteristics of MCI patients who progressed to DLB compared to those who progressed to AD dementia or remained stable.METHODSConsecutive MCI patients who underwent single voxel MRS at baseline and progressed to DLB (n = 10) were identified during a median follow‐up period of 18 months. From the same cohort, we identified age‐ and sex‐matched MCI patients who progressed to AD dementia (n = 27) or remained stable (n = 20) during a similar follow‐up period. This study was approved by the Institutional Review Board and informed consent was from every subject.RESULTSMCI patients who progressed to AD dementia were characterized by lower N‐acetylaspartate (NAA)/Cr ratio in the posterior cingulate voxel compared to those who progressed to DLB (P = .001). Decreased NAA/Cr in the posterior cingulate voxel differentiated MCI patients who progressed to DLB from those who progressed to AD with an area under the receiver operating characteristic curve of .85 (P < .001) on logistic regression analysis.CONCLUSIONSMRS may be useful in differentiating MCI patients with prodromal AD dementia from those with prodromal DLB for early disease‐specific interventions.

Background and purposeSome recent studies in older, largely white populations suggest that vitamin D, measured by 25‐hydroxyvitamin D [25(OH)D], is important for cognition, but such results may be affected by reverse causation. Measuring 25(OH)D in late middle age before poor cognition affects behavior may provide clearer results.MethodsThis was a prospective cohort analysis of 1652 participants (52% white, 48% black) in the Atherosclerosis Risk in Communities (ARIC) Brain MRI Study. 25(OH)D was measured from serum collected in 1993–1995. Cognition was measured by the delayed word recall test (DWRT), the digit symbol substitution test (DSST) and the word fluency test (WFT). Dementia hospitalization was defined by ICD‐9 codes. Adjusted linear, logistic and Cox proportional hazards models were used.ResultsMean age of participants was 62 years and 60% were female. Mean 25(OH)D was higher in whites than blacks (25.5 vs. 17.3 ng/ml, P < 0.001). Lower 25(OH)D was not associated with lower baseline scores or with greater DWRT, DSST or WFT decline over a median of 3 or 10 years of follow‐up (P > 0.05). Over a median of 16.6 years, there were 145 incident hospitalized dementia cases. Although not statistically significant, lower levels of 25(OH)D were suggestive of an association with increased dementia risk [hazard ratio for lowest versus highest race‐specific tertile: whites 1.32 (95% confidence interval 0.69, 2.55); blacks 1.53 (95% confidence interval 0.84, 2.79)].ConclusionsIn contrast to prior studies performed in older white populations, our study of late middle age white and black participants did not find significant associations between lower levels of 25(OH)D with lower cognitive test scores at baseline, change in scores over time or dementia risk.