Impact of cystatin C and microalbuminuria on cognitive impairment in the population of community-dwelling Japanese.

Background and Aims: Cognitive impairment is an important element affecting our well-being, and as such, early diagnosis is critical today. We investigated whether serum cystatin C and microalbuminuria are associated with cognitive impairment.
Methods: A total of 1943 subjects (774 males, 1169 females, mean age 65.8 years) took part in the investigation, and underwent a health examination in Tanushimaru, Japan, in 2009. The participants' cognitive function was evaluated using of mini-mental state examination (MMSE). We measured the levels of serum cystatin C using latex nephelometric immunoassay. Spot urine samples were used to measure microalbuminuria levels. Multivariate linear regression analyses were used to assess the relationship between MMSE scores and the level of cystatin C or microalbuminuria. All statistical analyses were performed using the SAS system.
Results: The mean values of log-transformed serum cystatin C levels and log-transformed microalbuminuria were 0.95 (range 0.41-7.11) mg/L and 10.7 (range 1.1-2600) mg/g·Cr, respectively. The means of MMSE score were 27.7 ± 2.5. In the multivariate linear regression analyses adjusted for age and sex, MMSE was significantly associated with systolic blood pressure (p = 0.024, inversely), cystatin C (p = 0.046, inversely) and microalbuminuria (p = 0.019, inversely), whereas estimated glomerular filtration rate (eGFR) had an insignificant association (p = 0.197). In the multiple stepwise linear regression analysis, age, history of stroke, systolic blood pressure, serum cystatin C were independently associated with MMSE levels.
Conclusions: We demonstrated for the first time that cognitive function was significantly and inversely associated with cystatin C and microalbuminuria, in the relatively younger general population.
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