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Preventing Alzheimer Disease

At first read, the study results seemed disappointing. Yet another promising premise fails to deliver when it comes to actual proof.

But the researchers aren’t ready to give up on this hypothesis just yet.

In fact, commentators on the study say the results offer ‘great hope’ and represent ‘a major leap forward.’

The SPRINT MIND study, recently published in JAMA was investigating whether intensive blood pressure control (to a systolic less than 120mmHg) worked better than standard blood pressure control (SBP<140mmHg) at reducing the risk of mild cognitive impairment and dementia.

This randomised controlled trial was a component of the well-publicised Systolic Blood Pressure Intervention Trial (SPRINT) which looked at the effect of more intensive blood pressure control on cardiovascular and renal outcomes in addition to cognitive function in over 9000 people without a history of diabetes or stroke.

Basically, what this study showed was that intensive blood pressure control to a target of less than 120mmHg did not reduce the incidence of probable dementia compared to lowering BP to a target of less than 140mmHg.

Depressing, yes? No, say the study authors.

Firstly, they say the study demonstrated no ill-effects of intensive BP lowering – which has been an issue of concern for some who have been worried that lowering the BP could decrease cerebral perfusion thereby harming cognitive function. In fact, the study authors showed quite the opposite was true. The intervention actually helped protect cognitive ability.

“This is the first trial, to our knowledge, to demonstrate an intervention that significantly reduces the occurrence of [mild cognitive impairment], a well-established risk factor for dementia, as well as the combined occurrence of [mild cognitive impairment] or dementia,” they said.

The study authors suggest the lack of benefit in dementia may be due to the fact the SPRINT study was terminated early following the demonstration of benefit of intensive BP control on cardiovascular outcomes and all-cause mortality. Because of this shortened time frame and the fact that there were fewer than expected cases of dementia, they suggest the study may have been ‘underpowered’ to show a result for lowering the risk of dementia.

They also say there were fewer cases of dementia among the intensive treatment group compared with the standard treatment group (7.2 vs 8.6 cases per 1000 patient years) even though this wasn’t statistically significant. We cannot know whether this trend would have reached statistical significance had the intervention continued.

An accompanying editorial views the study and the results with a good deal of positivity.

“For older adults, almost all of who have concern about being diagnosed with Alzheimer Disease and related dementia, [this study] offers great hope,” the US epidemiologist, Dr Kristine Yaffe, said.

She points out that this a readily modifiable risk factor, and we should be accelerating our efforts into investigating whether this, along with other vascular health interventions such as physical activity, can indeed prevent dementia, building on the positive results of this study.

“The SPRINT MIND study may not be the final approach for prevention of Alzheimer disease or other cognitive impairment but it represents a major leap forward in what has emerged as a marathon journey.”

Reference

Yaffe, K. Prevention of Cognitive Impairment With Intensive Systolic Blood Pressure Control. JAMA [Internet]. 2019 Jan 28. DOI: 10.1001/jama.2019.0008 [Epub ahead of print]