There's one part of the body you don't want to see get smaller--and no, men, it's not down there.

It's the brain--and while we all lose a little grey matter as we age, too much shrinkage has been linked to dementia.

Now, a new study finds that the loss of brain mass found in Alzheimer's patients might actually be detectable up to a decade before the telltale signs of the disease appear.

Researchers looked at two groups of 33 healthy people in their 70s who were given MRI scans of the regions of the brain associated with Alzheimer's disease, and then tracked for between 8 and 11 years.

The researchers say 55 percent of the 11 people who had the lowest MRI measurements eventually developed Alzheimer's disease... versus none of the nine people with the highest measurements and just 20 percent of those with normal readings, according to the study in Neurology.

A similar study in 2009 found that people with smaller hippocampal volumes and faster shrinkage rates were between two and four times more likely to develop dementia than people with larger hippocampal volumes and slower rates of shrinkage.

Like I said earlier, all brains shrink with age--so don't worry about the normal loss of volume, which is about half a percent a year in seniors.

More than that, however, and you still don't have to accept dementia as your fate. In fact, you might even be able to slow that shrinkage with ordinary B vitamins.

Researchers found that a patented blend of folate, B12 and B6 slowed the rate of brain shrinkage by an average of 30 percent when compared to a placebo in a study of 168 seniors who suffered from mild cognitive impairment.

The patients who had the highest levels of the inflammation marker homocysteine had an even greater benefit, with the B blend lowering their shrinkage rates by 53 percent. (Read about that here.)

Brain shrinkage isn't the only dementia warning sign to watch for--another new study finds that people who lose the ability to detect lies and sarcasm may actually suffer from frontotemporal dementia, a form of the disease that affects about 5 percent of all dementia patients.

Researchers from U.C. San Francisco asked 175 older adults--half of whom had some form of dementia--to watch videos of two people speaking, one of whom occasionally lied or used sarcasm.

While the patients without dementia had no problems picking up on it, the ones who showed signs of frontotemporal dementia missed it.

Two messages from this: First, if someone in your life starts missing sarcasm and lies, it may be time to bring them to a specialist.

And second, if they do have this form of dementia, they may be especially prone to scams and con artists--so keep a close eye on them and their finances.