Introduction: Cognitive decline and heart failure frequently coexist in the elderly. Several studies have been shown that current smoking was paradoxically associated with preserved cognitive function. However, the mechanism underlying the relationship between smoking status and cognitive function in chronic heart failure (CHF) was not clear.
Hypothesis: We hypothesized that physical activity might mediate the association between smoking and cognitive function in the elderly patients with CHF.
Methods: Cognitive function was evaluated using mini-mental state examination (MMSE) in 152 elderly inpatients in stable phase of HF (82.8±6.2 years old, female 51%, smoking 26%). Standing isometric relative handgrip strength was calculated as the average level of maximal absolute handgrip strengths from both hands. Total exercise capacity was assessed with the 6MWT.
Results: According to the quartile of MMSE score (≥ 24), a significant association of MMSE score were observed with prevalence of current smoking (38 vs 22%, p<0.05) while handgrip strength (15.5 vs 12.9kg, p=0.13) and 6MWT (179 vs 149m, p=0.15) were not significantly different between the two groups. In the logistic regression analysis adjusted for the confounding factors including age, gender, body weight, left ventricular ejection fraction, log brain natriuretic peptide, systolic blood pressure and use of antihypertensive medication, current smoking (β=3.25, 95%CI: 1.08 to 9.80, p<0.05) was significantly associated with highest MMSE score. Consistent with handgrip strength or 6MWT as mediators of the relationship between smoking and highest MMSE score, inclusion of handgrip strength or 6MWT in the multivariate model appreciably attenuated the association (p=0.06 and p=0.09, respectively).
Conclusions: In the elderly patients in stable phase of CHF, the current smoking was significantly associated with higher cognitive function. Handgrip strength or 6MWT was a significant mediator for the relationship between smoking and cognitive function in the CHF patients. Preservation of physical activity might be a key factor for preserved cognitive function in the elderly smokers with CHF.