Photo: Adam Berry (Getty Images)

Some five million Americans live with dementia, most often Alzheimer’s disease. And it’s almost certain that as the general population gets older, dementia will become more common. But a new study published this week offers some encouraging, if mixed, news.

It might be possible to prevent cognitive decline by aggressively treating a person’s high blood pressure, the study found. Unfortunately, it’s not clear whether lowering blood pressure can do the same for dementia.

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In 2010, a project known as the Systolic Blood Pressure Intervention Trial, or SPRINT, was started. It recruited nearly 10,000 volunteers over the age of 50 with high blood pressure and at least one other risk factor for cardiovascular disease, like smoking. The trial was meant to compare whether trying to lower people’s systolic blood pressure (the top number in a blood pressure reading) below 120 would be better for people’s overall health than trying to lower it to 140. The latter threshold was, at that point, considered standard care.

Cardiovascular disease was the main health outcome examined by the SPRINT study, which ended early in 2015 after it became apparent that aiming for 120 was better at preventing things like heart attacks and stroke than standard care. But a subset of around 8,500 volunteers were also studied for their potential risk of dementia and mild cognitive impairment (MCI), an earlier stage of memory loss and brain drain that often progresses to dementia.

The findings of the current study, published Monday in JAMA, come from this side project, called the SPRINT MIND study. It found that aggressively treated, relatively healthy people were significantly less likely to develop MCI than people given standard care. The rate of new MCI cases was 19 percent lower in this group.

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High blood pressure is a risk factor for all sorts of conditions, including cognitive decline. But while scientists largely accept that keeping our blood pressure in check should help prevent dementia, we don’t currently have concrete evidence from human trials that any potential intervention can lower dementia rates. So the results of the SPRINT MIND are definitely good news in that sense.

But there’s also a big caveat to the study. Ultimately, while there was a small reduction in new cases of full-blown dementia in the aggressive treatment group, it wasn’t a statistically significant difference from the group given standard care. In other words, the study actually failed to meet its primary outcome.

Ordinarily, it might be easy to dismiss the touted results of the SPRINT MIND study as overblown hype. But there’s a key point to take into account. While not every person with MCI goes on to develop dementia, everyone with dementia will first experience MCI. And because the study was ended early, it’s possible researchers simply didn’t have the time needed to spot a true reduction in dementia cases.

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“The fact that there was still a MCI result when the study was cut short makes these results encouraging,” Laurie Ryan, chief of the Dementias of Aging Branch at the National Institute on Aging, said in a statement (the NIH helped fund the original SPRINT study).

So while the study isn’t a home run for dementia prevention, it’s a promising lead. In light of the findings, the Alzheimer’s Association announced Monday that it would help fund SPRINT MIND 2.0, an extension of the original study that should provide two more years of follow-up data.

“The Alzheimer’s Association finds these data to be compelling, and is committed to getting clarity and certainty on the dementia outcome by following participants for a longer period of time,” Maria Carrillo, chief scientific officer of the Alzheimer’s Association, said in a statement.

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Hopefully, time really will tell if lowering blood pressure can prevent dementia.

[JAMA via NIH, Alzheimer’s Association]