Sex differences in salt-sensitivity risk approximated from ambulatory blood pressure monitoring and mortality

Background: Salt-sensitivity is difficult to assess with salt diet. Methods: Salt-sensitivity risk was estimated from ambulatory blood pressure monitoring indices, patient data, and 20-year all-cause mortality. Tracings of 2064 untreated patients from our clinical monitoring service were evaluated for the prevalence and associations of salt-sensitivity risk, which was considered low in patients with both mean arterial pressure dipping more than 10% and 24-h heart rate less than 70 bpm; high in patients with dipping 10% or less and 24-h heart rate at least 70 bpm; and intermediate in patients with the other combinations. Results: Low, intermediate, and high salt-sensitivity categories were predicted for 33% (366/1099), 57% (624/1099), and 10% (109/1099) of men and 18% (177/965), 67% (630/965), and 16% (158/965) of women, respectively (chi(2) P < 0.0001). Positive linear trends were noted between salt-sensitivity and BMI, clinic and 24-h ambulatory blood pressure, awake and sleep ambulatory heart rate and awake and sleep blood pressure variability, and negative trend with heart rate dipping (all P < 0.005). Kaplan-Meier analyses revealed increased mortality in association with salt-sensitivity in men but not in women (P < 0.02). With low and intermediate salt-sensitivity as reference, adjusted Cox proportional hazard ratios for all-cause mortality associated with high sensitivity were 1.96 (95% confidence interval 1.07-3.62) in men and 1.02 (0.51-2.07) in women. Conclusion: To the extent that ambulatory blood pressure-derived estimation of salt-sensitivity is feasible, analysis of our database suggests increased mortality risk in men but not in women, in whom salt-sensitivity was more common.