Sex- and age-dependent relationships between resting heart rate and cognitive impairment: a population-based cross-sectional study in rural China

Resting heart rate (RHR) is an important risk factor for cardiovascular diseases (CVD) and has been linked to cognitive impairment (CI), but evidences remain inconsistent. Given that both cardiovascular regulation and cognitive function differ by sex and age, these factors may modify the RHR–CI association. This study aimed to examine this relationship and its potential sex- and age-specific differences in a general Chinese population. This population-based cross-sectional study included 1309 participants from rural areas of northwestern China. RHR was obtained from a standard 12-lead electrocardiogram. CI was diagnosed with Mini-Mental State Examination scores below the cutoff value. RHR data were fitted as restricted cubic spline to explore potential non-linear relationships. Stratified analyses by sex, age (50–69 years vs ≥ 70 years) and combined were performed. Two hundred twenty five (17.2%) participants met criteria for CI. We found an independent and prominent U-shaped relationship between RHR and CI in female within 50–69 years (P overall = 0.01, P non-linear = 0.003), while other subgroups showed no significant relations. Further results showed that in female within 50–69 years, both lower (≤ 70 bpm) and higher RHR group (≥ 81 bpm) were associated with increased risk for CI (vs. 71–80 bpm) (≤ 70 bpm vs 71–80 bpm vs ≥ 81 bpm: 19.3% vs 10.7% vs 18.5%, P = 0.011; ≤ 70 bpm vs 71-80 bpm: OR = 2.061(1.225–3.467), P = 0.006; ≥ 81 bpm vs 71-80 bpm: OR = 1.692(0.949–3.015), P = 0.075). This association remained significant after excluding participants with abnormal RHR or with CVD or cerebrovascular diseases. The relationship between RHR and CI was highly dependent on sex and age. An independently U-shaped relationship existed only in female within 50–69 years, but no relations were found in other participants. These findings highlight the importance of considering demographic heterogeneity when evaluating the relationship between RHR and CI.