Sense of smell can start to fade up to 10 years before memory changes become noticeable. The olfactory system — the nose and the brain areas that process smell — is one of the first regions to change as the brain ages. That makes smell one of the earliest windows you have to pay attention and act.

Long-term blood sugar health and hearing are closely linked. Research shows that people with elevated blood sugar face about double the rate of hearing loss — likely because it affects the small blood vessels and nerves of the inner ear. Tracking your hearing over time shows you the trend while it's still gradual.

Mood and taste move together. Low mood is associated with dulled or distorted taste, which changes appetite and nutrition — and the loop feeds itself. Noticing a shift in how food tastes is worth paying attention to.

Nerve sensation in the feet and lower limbs fades gradually and quietly, which makes it easy to miss until an injury goes unnoticed. Regular touch testing makes a slow change visible early, when there's the most room to act on it.

Difficulty understanding speech in noise is often less about the ears than about how the brain processes sound — and that processing can change early. Measuring it over time separates 'the room was loud' from a real trend.