Final answer:
The greatest rate of aging is generally observed during late adulthood, starting in the mid-60s, where serious health concerns and physical and cognitive decline become more pronounced.
Step-by-step explanation:
The rate of aging does not stay constant throughout life; it varies from one stage of adulthood to another. While aging signs can start to manifest in the late 20s and early 30s, these changes tend to be gradual and subtle. However, the greatest rate of aging is generally observed during late adulthood, which begins in the mid-60s.
In late adulthood, the skin continues to lose elasticity, reaction time slows more dramatically, and muscle strength diminishes. Senses such as smell, taste, hearing, and vision, which are sharp in our twenties, decline significantly. Cognitive functions also face more serious challenges during this stage, with increased risks of memory loss, dementia, and diseases like Alzheimer's disease.