10 people over the age of 65 have dementia. It is the single greatest cause of disability in older Australians . Rates of dementia are higher for indigenous people. In people from the northern territory and western Australia the prevalence of dementia is 26 times higher in the 45–69 year old group and about 20 times greater in 60–69 year old group. Risk factors in countries of affluence The risk factors for developing dementia or Alzheimer's include age, family history, genetic factors, environmental factors, brain injury, viral infections, neurotoxic chemicals, and various immunological and hormonal disorders. A new research study has found an association between the affluence of a country, hygiene conditions and the prevalence of Alzheimer in their population. According to the Hygiene Hypothesis, affluent countries with more urbanized and industrialized areas have better hygiene, better sanitation, clean water and improved access to antibiotics. This reduces the exposure to the friendly bacteria, virus and other microorganisms that help stimulate our immune system. Decreased microbial exposure leads to immune system that is poorly developed, which exposes the brain to inflammation as is seen in Alzheimer's disease. Countries like the UK and France that have access to clean drinking water, improved sanitation facilities and have a high GDP show a 9% increase in Alzheimer's disease as opposed to countries like Kenya and Cambodia. Also countries like UK and Australia, where three quarters of their population lives in urban areas, have a 10% higher Alzheimer's rate than in countries like Bangladesh and Nepal where less than one tenth of their population live in urban areas. Alzheimer's risk changes with the environment. Individuals from the same ethnic background living in an area of low sanitation will have a lower risk as compared to the same individuals living in an area of high sanitation who will be exposed to a higher risk of developing Alzheimer's. An African-American in U.S. has a higher risk of developing Alzheimer's as compared to one living in Nigeria. Immigrant populations exhibit Alzheimer disease rates intermediate between their home country and adopted country. Moving from a country of high sanitation to a country of low sanitation reduces the risk associated with the disease. Mental illness People who face poverty have more risks related to having a mental illness and also do not have as much access to treatment. The stressful events that they face, unsafe living condition and poor physical