Once people reach the age of 65, they begin to experience memory problems, most of which is caused by Alzheimer's disease. This is a terrible disease that causes patients to loss memory, starting with recent events and slowly taking away more of their memory from longer ago. This means that AD patients have a hard time remember what they did earlier this week, but they do remember important events from years ago, until the disease progresses and starts taking away those memories.
This disease is caused by senile plaques and neurofibrillary tangles, which cause a loss of synapses and the death of cells in the hippocampus and cerebral cortex which are important to memory and intellectual ability. Unfortunately there are no treatments or cures that slows down or reverses Alzheirmer's effects, there are only proposed theories as to what can help, yet they have not been proved by research. One of these theories that has been studied showed that being physically fit, with a good diet and a strong social network can help decrease ones chances of Alzheimer's, but it's hard to determine the correlation in the study. Because of the difficulty to treat Alzheimer's, people who have the disease gradually lose their memories until they pass away.