A clear correlation exists between increasing age and the chances of developing dementia. In fact, less than 1 percent of people are diagnosed under the age of 65. The following table breaks down these figures.
The obvious question is whether dementia will become more common as people live longer. Thanks to advances in science, medicine, and technology, the human species is living increasingly longer. Life expectancy until 30,000 years ago is believed to have been less than 30 years, and right up until the 1800s it was common for adults to die by the age of 40. Now the average man in the United States can expect to live for 76.4 years, whereas a woman can make it to the ripe old age of 81.2.
| Age | Number diagnosed |
| Younger than 65 | 1 in 1,500 |
| 65–70 | 1 in 100 |
| 71–79 | 1 in 20 |
| 80–89 | 1 in 4 |
| 90+ | 1 in 3 |
These figures represent an average, and life expectancy across the United States varies depending on levels of poverty and other factors. To the same extent, life expectancy in some countries is much lower than in the United States; in the African nation of Chad, for example, it's only 49.5 years.
Over the next few decades these figures are expected to rise along with the proportion of older people in the population as a whole. According to government figures, currently 44 million people in the United States are older than 65 years of age. By 2030, it's estimated that 25 million more elderly people will be residing in the United States, rising to around 79 million by 2050.A boy born in the United States in 2030 will have a good chance of living until he's 85, and a girl to 90. Given the rising chance of developing dementia with age, it's feared that cases will become far more common as a result of this boom in life expectancy.
