Fig. 2.

Relationship between MMSE score (95% confidence interval) and napping frequency. Adjusted for age, gender, years of education, smoking habit, regular alcohol, tea and coffee consumption, habitual snoring, depression (Geriatric depression scale score ≥ 8), use of psychotropic medications, and the diagnosis of diabetes mellitus, hypertension, stroke, chronic obstructive pulmonary disease and coronary heart disease. p for quadratic regression = 0.017. 0 to ≤1–2/week: p for trend = 0.026; ≥1–2/week to daily: p for trend = 0.026