Parathyroid hormone (PTH) does not have an independent influence on cognitive decline, according to a recent population-based cohort study. Researchers studied 12,964 middle-aged white and black Atherosclerosis Risk in Communities Study (ARIC) participants without a history of prior stroke. In 1990–1992 (baseline), subjects had serum PTH levels measured and cognitive function testing, with repeat cognitive testing performed at up to 2 follow-up visits. Cognitive testing included the Delayed Word Recall, the Digit Symbol Substitution, and the Word Fluency tests, which were summed as a global Z score. The mean (SD) age of the cohort was 57 (6) years and 57% were women. They found:

• There was no cross-sectional association of elevated PTH with cognitive global Z score at baseline.
• Over a median of 20.7 years, participants in each PTH quartile showed a decline in cognitive function.
• However, there was no significant difference in cognitive decline between each of the top 3 quartiles and the lowest reference quartile.