[Do the morning peak in blood pressure, age and gender affect the need to change hypertension treatment because of inefficacy?].

Objective: To evaluate if the timing coincidence of morning rise of arterial blood pressure (BP) and morning turn of clinic BP measurement in our primary healthcare center implies an increased risk of switching antihypertensive drugs because of inefficacy with respect to afternoon staff turn. We also describe age and sex differences. DESIGNAND SETTING: A historical cohort study. We recorded all changes of antihypertensive drugs because of inefficacy of patients of 7 urban primary care clinics during the period from october 1997 to september 1999.

Measurements: We compared the incidence of changes per 1000 months of prescription of morning and afternoon turns, men and women, older and younger patients than 75 and 65 years old.

Results: The mean age of 1152 patients was 69.5 years old. The relation men:women in morning and afternoon turns was similar. Relative risk of switching in morning/afternoon turns was 0.82 (95% CI, 0.61-1.10). Sex and age did not affect the results. If the turn was not considered, younger patients and men had increased risk of being switched. Male adults (< 65 years old) relative risk against female was 1.62 (95% CI, 1.07-2.47). Older patients than 65 year had the RR inverted: RR men/women: 0.78 (95% CI, 0.51-1.21).

Conclusion: Morning rise of BP did not provoque an increased risk of switching antihypertensive drugs in morning turn with respect to afternoon turn. Male adults had increased risk of switching with respect to women. Older women than 65 years old had more risk than men to be changed.