AIMS

 1) To assess the relationship between nocturnal dipping of blood pressure (ND), urinary sodium excretion (24h UNa) in hypertensive patients with type 2 diabetes and habitually high (sodium excretion >200 mmol/24 h) or low (sodium excretion <100 mmol/24 h) salt intake. 2) To determine if the relationship between ND and 24h UNa is influenced by morning ARB with or without salt supplementation.

METHODS

28 Patients received 4 weeks of ARB (telmisartan, 40mg mane) and in a double-blind randomised fashion, sodium chloride (NaCl, 100 mmol/24 h) or placebo capsules in addition to their habitual salt intake during the last 2 weeks of telmisartan therapy. The protocol was repeated with NaCl and placebo capsules administered in reverse order to allow each participant to act as his or her own control. At 0, 4 and 18 weeks, 24 h ambulatory blood pressure (ABP) and 24 h urine collections were performed. The ND (%) was calculated as = ((MAP day- MAP night)/MAPDay) x 100, where MAPDay and MAPNight are daytime and night time values of MAP.

RESULTS

Correlation between ND of MAP (mmHg)   and 24h UNa:

There was a significant correlation between the 24h UNa and the ND before the commencement of telmisartan which disappeared during telmisartan therapy but was restored with NaCl supplementation.

CONCLUSION

In type 2 diabetes, the degree of ND correlates with urinary sodium excretion and suggests that dietary salt intake increases blood pressure to a greater extent during the day than night. This correlation is abolished by telmisartan administered in the morning. This study raises the possibility that evening administration of telmisartan may restore ND in subjects with low dietary salt intake.