Cardiovascular Risk Factors and Memory Function in Nepal: Findings from the Dhulikhel Heart Study

BACKGROUND

Although a growing number of studies are focusing their attention on cognitive domains, fewer studies have been conducted in developing countries. Previous studies have suggested that cardiovascular disease (CVD) risk factors may be related to cognitive health or impairment. In the present study, we assessed the associations of CVD risk factors with short-term memory and working memory function among 352 adults from the city of Dhulikhel in Nepal.

METHODS

This cross-sectional study used data from the first wave of the Dhulikhel Heart Study (DHS), which was a population-based cohort study to investigate CVD and its risk factors in Nepal. Information on demographics and self-reported CVD risk factors were collected via home interviews. Blood pressure and Body Mass Index (BMI) were clinically measured by trained technicians. Unadjusted and demographic adjusted linear regression models quantified the correlations between CVD risk factors and the Digit Span Forward (DSF) and the Digit Span Backwards (DSB) tests, measures of short-term and working memory, respectively. Binomial and multinomial logistic regression models were used to evaluate the relationship of lowered short-term memory and working memory with CVD risk factors. Sensitivity analyses were performed among participants who had never taken any hypertension treatment.

RESULTS

A total of 32.8% of participants in the DHS (N=352) completed either the DSF or the DSB. In linear regression models adjusted for age, sex, education, ethnicity, and household, diabetes was associated lower DSF scores (Coeff=-0.74, p=0.05); however, hypertension and higher BMI were associated with higher DSF scores (Coeff. of hypertension=0.52, p=0.04; Coeff. of BMI=0.05, p=0.05). Other CVD factors did not result in significant relationships with DSF scores. In binomial logistic regression models, BMI was similarly associated with a reduced risk of lowered short-term memory comparing the lowest quartile of the DSF with the other three quartiles (RR=0.96, 95% CI 0.93-1.00). Former smoking was also associated with the reduced risk of lowered short-term memory (RR=0.57, 95% CI 0.39-0.83). Sensitivity analyses provided similar results although associations were attenuated due to reduced sample size (n=276). In the multinomial logistic regression model comparing the highest quartile with the lowest (worst memory) of the DSF, the relative risk for a one-unit increase in BMI and ≥600 MET min/week physical activity was 0.90 (95% CI 0.83-0.98) and 0.52 (95% CI 0.27-0.98), respectively. Working memory based on the DSB test was not significantly associated with any CVD risk factors in the present study.

CONCLUSION

Our results suggest that hypertension, diabetes, BMI, smoking history, and physical activity may be associated with short-term memory among Nepalese adults. Results should be considered cautiously due to the cross –sectional design of the study, small sample size and multiple testing.