Remember the seven dwarfs from the 1937 Disney classic "Snow White"? It turns out that Grumpy was setting himself up for big problems down the road, according to new research published in the journal Alzheimer's & Dementia.

The study reported that repetitive negative thinking (RNT) is associated with memory decline and brain deposits of amyloid tangles and tau protein, which are hallmarks of Alzheimer's disease.

The researchers evaluated the RNT of a subset of study participants and found that it didn't increase as the signs of Alzheimer's did. According to lead researcher Dr. Natalie Marchant, "The data support the hypothesis that RNT may be a risk factor for, rather than an early symptom of, dementia."

RNT may contribute to Alzheimer's because of stress associated with negative thinking, which can damage cognition. Stress also plays a role in amyloid- and tau-related brain changes.

Fortunately, you can become less grumpy with the following strategies:

• Research shows that small steps like smiling more (even for no reason) can boost your mood. So does adopting good posture. If you slump, you tend to grump.

• Focus on what you feel grateful for.

• Perform one kind act a day. It may be helping a stranger with a package, calling your grandmother, doing volunteer work for a local charity, or going out of your way to help a friend.

• Give yourself happy moments. A study in the Journal of Positive Psychology found that trying to make yourself happier does just that. For example, if you know you like a certain song, play it to boost your mood -- and it will.