Objectives: Microalbuminuria (MA) has been increasingly identified as a marker of cardiovascular risk. Although poor cognitive function has been implicated as a sequelae of increased cardiovascular burden, little is known about the association between MA and cognitive function.
Design: Population-based cross-sectional study.
Settings: National Health and Nutrition Examination Survey 1999-2002 in the USA.
Subjects: 2049 noninstitutionalized adults (>/=60 years) with nonmissing values in cognitive test, urinary albumin-to-creatinine ratio (UACR) and ankle-brachial blood pressure index (ABPI) was analysed. Participants with UACR >300 microg mg(-1) were excluded.
Main outcome measures: The UACR, in the unit of microg mg(-1), was calculated by dividing the urinary albumin value by the urinary creatinine concentration. MA was defined as UACR between 30 and 300 microg mg(-1). Cognitive function was measured by a 2-min Digit Symbol Substitution Test (DSST). Peripheral artery disease (PAD) was defined as an ABPI <0.9 in either leg.
Results: Overall speaking, MA was inversely associated with DSST score after controlling for age, sex, race, body mass index and educational level (regression coefficient = -2.8, P = 0.002). There was an effect modification of PAD on the association between MA and the DSST score. Amongst participants with PAD, the DSST score for those with MA was lower than those without MA (beta = -6.3, P = 0.003) after multivariate adjustment. Moreover, participants with PAD in the highest quartile of UACR had significantly lower DSST score compared to those in the lowest quartile (beta = -8.7, P = 0.001). There was no association between MA and cognitive function amongst participants without PAD. We observed an additive effect of MA and PAD on DSST score. Participants with both MA and PAD had a lower mean DSST score compared to those without both conditions (beta = -6.2, P = 0.003).
Conclusions: The presence of MA or a higher level of urinary albumin excretion was inversely associated with cognitive function in participants with PAD.