Normal EEG in adults of age 70 or older is similar to those younger with the following exception:

In older adults, particularly those aged 70 or older, there is a notable change in sleep architecture compared to younger individuals. One of the significant changes is that REM (Rapid Eye Movement) sleep tends to decrease, often falling below 20% of total sleep time. This reduction in REM sleep can be attributed to various factors associated with aging, which can affect sleep quality and quantity.

While the distribution of sleep states generally remains similar throughout life, older individuals may experience more fragmented sleep patterns and a decline in the duration of REM sleep, leading to the characteristic finding noted in the question. As such, this decrease is a key differentiating factor from younger adults, making it an appropriate choice regarding the exception found in the normal EEG patterns across different age groups.

In contrast, while other aspects of the EEG may change with age, such as beta activity and slow wave prominence, these characteristics vary more individually and are not as universally applicable across the older adult population as the reduction of REM sleep. Additionally, the notion that alpha activity becomes more reactive or that beta is rarely seen does not consistently hold true across all elderly individuals. Therefore, the decline in REM sleep stands out as a more defining and commonly recognized characteristic in distinguishing the EEG of older adults from