Q: Which of your senses deteriorates first with age?
A: Taste. The number of taste buds you have decreases with age, and each remaining taste bud also shrinks, reducing sensitivity. In addition, your mouth produces less saliva as you age, further impairing sense of taste.
Smell also diminishes with age, especially after age 70. In some ways the impairment is similar to loss of taste as the nose produces less mucus, which helps keep odors in the nose long enough to be detected by nerve endings.
Of course, vision and hearing also decline with age, and may be exacerbated by disease or environmental factors, such as smoking or excessive noise. Touch changes too, though less obviously. Decreased blood flow to nerve endings in the skin can reduce sensitivity, but thinner skin may increase it.