The association between serum cholesterol levels and mild-to-moderate cognitive impairment in the Suita Study and evidence from other epidemiological studies.

Background: Serum cholesterols are well-documented markers of cardiovascular diseases; however, their association with cognitive well-being is uncertain. This study investigated the association between serum cholesterol levels and mild-to-moderate cognitive impairment.

Methods: Epidemiological evidence on the role of total cholesterol (TC), high-density lipoprotein cholesterol (HDLC), non-HDL-C, and low-density lipoprotein cholesterol (LDL-C) in cognitive impairment was highlighted. Then, data from 6216 Japanese individuals, aged ≥50 years, from the Suita Study were analyzed. Mini-Mental State Examination (MMSE) scores <27 and < 24 were used to define cognitive impairment. Logistic regression was used to calculate the odds ratios (ORs) and 95 % confidence intervals (95 % CIs) for cognitive impairment.

Results: Epidemiological studies investigating the association between serum cholesterol and cognitive impairment have shown conflicting findings: elevated risk with certain lipid components in some studies and no association in others. In the Suita Study, HDL-C < 40 mg/dL was associated with cognitive impairment: ORs (95 % CIs) = 1.36 (1.08, 1.72) for MMSE <27 and 1.61 (1.00, 2.60) for MMSE <24. Non-HDL-C ≥ 200 mg/dL was also associated with cognitive impairment: ORs (95 % CIs) = 1.53 (1.02, 2.31) for MMSE <27 and 1.80 (1.16, 2.79) for MMSE <24. No such associations were detected with TC.

Conclusion: While epidemiological evidence remains inconsistent, the Suita Study showed that decreased HDL-C and increased non-HDL-C, but not increased TC, were associated with mild-to-moderate cognitive impairment. Management of serum cholesterol levels should be considered to prevent cognitive impairment.