Alzheimer's disease
People who have Alzheimer's disease slowly lose their memory and ability to think clearly. As the disease gets worse, they get more confused and start acting differently. Several changes happen in the brain that stop it working properly. Small lumps called amyloid plaques grow in the parts of the brain used for memory and thinking. And bundles of twisted threads called 'neurofibrillary tangles' form inside brain cells. These stop brain cells communicating with each other, and they can cause cells to die. Also, in Alzheimer's disease, the brain does not have enough chemical messengers (neurotransmitters), and holes or gaps appear where brain cells have died.

Lewy body dementia
People with Lewy body dementia slowly lose their memory and ability to think clearly. Most people also get symptoms of Parkinson's disease. This means they may move more slowly and become rather stiff and rigid in the way they do things. People with this type of dementia get small, round clusters of proteins inside their brain cells. These are called Lewy bodies. They stop important chemicals in the brain from working normally. Lewy body dementia can also cause small lumps in the brain called amyloid plaques. They're made of protein and bits of dead cells. The lumps grow in the parts of the brain used for memory and thinking. They may stop messages from passing between brain cells.Lewy body dementia is the second most common cause of dementia after Alzheimer's disease.

vascular dementia
This type of dementia happens when blood vessels near your brain get damaged, so your brain doesn't get enough blood. Some of the cells in your brain die, which causes symptoms such as confusion and memory problems. Vascular dementia can happen suddenly if you have a stroke. Or it can come on gradually if you have a series of little strokes (this is called multi-infarct dementia).

high blood pressure
Your blood pressure is considered to be high when it is above the accepted normal range. The usual limit for normal blood pressure is 140/90. If either the first (systolic) number is above 140 or the lower (diastolic) number is above 90, a person is considered to have high blood pressure. Doctors sometimes call high blood pressure "hypertension."

stroke
You have a stroke when the blood supply to a part of your brain is cut off. This damages your brain and can cause symptoms like weakness or numbness on one side of your body. You may also find it hard to speak if you've had a stroke.

menopause
When a woman stops having periods, it is called menopause. This usually happens around the age of 50.

hormone replacement therapy
Hormone replacement therapy (also called HRT) is given to women after menopause to replace the estrogen (the main female hormone) that is no longer made by their ovaries. It can be given either as estrogen alone or as a combination of estrogen and progestin (another female hormone). It is useful to treat menopausal symptoms such as hot flushes, and to prevent brittle bone disease (osteoporosis). But there are concerns that it may increase the risk of breast cancer, heart attacks and strokes.

genes
Your genes are the parts of your cells that contain instructions for how your body works. Genes are housed on chromosomes, structures that sit in the nucleus at the middle of each of your cells. You have 23 pairs of chromosomes in your normal cells, each of which has thousands of genes. You get one set of chromosomes, and all of the genes that are on them, from each of your parents.

Down syndrome
Down's syndrome affects some people from birth. It causes learning difficulties, and it also makes some physical problems more likely. It is caused by an extra chromosome. Chromosomes are found in all our cells, and contain genes, which tell cells how to grow and behave.