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Older individuals who stuck with their antihypertensive drug treatment tended to have a lower longer-term risk of mortality, with the magnitude of benefit varying across the spectrum of clinical status, according to researchers from Italy.

Seniors had a lower likelihood of all-cause mortality with very high versus very low adherence, although the impact on risk waned with declining clinical status: −44% with good status, −43% with medium status, −40% with poor status, and −33% with very poor status (P=0.046 for trend).

Better adherence was also associated with a lower risk of cardiovascular mortality, Giuseppe Mancia, MD, PhD, of University of Milano-Bicocca, Italy, and colleagues reported.

"This supports the conclusion that antihypertensive treatment is beneficial in frail old patients but that the extent of the benefit may be less than that achieved by healthier old individuals," they wrote in a study in Hypertension.

The study was based on more than 1.28 million people age 65 and older (mean 76 years) who lived in the Lombardy region of Italy. As the country's National Health Service covers virtually all citizens, the investigators were able to retrieve fairly comprehensive medical records from various databases for their analysis.

People included in the analysis were those who had at least three consecutive prescriptions of antihypertensive drugs in 2011-2012. They were followed for a median of 7 years.

The Multisource Comorbidity Score -- to predict mortality in the Italian population -- was used to stratify participants clinical status.

As expected, death rates ranged from 16% for those in good status to 64% for those in very poor condition.

Very high adherence was defined as having more than 75% of follow-up time covered by antihypertensive prescriptions. Very low adherence flagged people who had less than 25% of their time covered by prescriptions.

Mancia's group matched 255,228 people who died during the 7-year observation period with surviving controls in a nested case-control analysis.

Compared with controls, the people who died more were more likely to have been on only one antihypertensive medication, to have been on other medications, and to have more comorbidities. Controls were more adherent with their BP-lowering treatment.

The investigators could only assume that they were prescribed, they acknowledged. Their study also lacked information on baseline and , they said.

Importantly, the possibility of residual confounding could not be excluded due to the study's retrospective design.

However, "the sensitivity analysis showed that only an extremely important, and thus unrealistic, involvement of an unmeasured confounder would have nullified the effect of adherence on mortality in patients with a very poor clinical status, which makes it most likely that adherence to antihypertensive treatment was independently responsible for the results," Mancia and colleagues maintained.

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