Which of the following EEG changes is commonly observed in elderly patients?

In elderly patients, irregular sleep spindles are a notable EEG change. Sleep spindles are bursts of oscillatory brain activity that occur primarily during non-REM sleep and are believed to play a role in memory consolidation and neural plasticity. As individuals age, the structure and function of the brain undergo changes, which can lead to alterations in the characteristics of sleep spindles, making them appear more irregular compared to those seen in younger individuals. This irregularity can be a reflection of the aging process and may be associated with variations in synaptic activity or other neurophysiological changes that accompany aging.

While other options might present changes in EEG patterns, irregular sleep spindles specifically capture the unique aspect of how aging affects the brain's electrical activity during sleep, making it the most relevant and accurate choice in this context.