My grandma has been having difficulty speaking clearly recently, is this a problem or just old age?

Recently I've noticed that my grandma has been having difficulty pronouncing words that should be fairly simple.. She knows what she wants to say, she just can't form the word correctly. For example, she was trying to say differentiate the other day and corrected herself about 10 times before finally giving up. Is this just normal as people get older, or should I be concerned that something more serious may be going on?