The Merck Manual [Changes in the Body
with Aging] says, “Most bodily functions
peak shortly before age 30 and then begin
a gradual but continuous decline.”

Bones become less dense, Merck
Manual says, which raises the risk of
fractures. Changes in the vertebrae at the
top of the spine “cause the head to tip
forward, compressing the throat.” That
makes swallowing more difficult, thus
raising the risk of choking.

Cartilage thins, often leading to
osteoarthritis, Merck says. Muscle tissue
and strength start to decrease early in
the aging process — at around age 30.
Presbyopia, the stiffening of the lens in
the eyes, typically begins at age 40: That’s
when people notice a loss of “near vision,”
or objects less than two feet away. And,
Merck says, as we age, we need more
light to see, our color perceptions change
(which can make text written in certain
colors harder to read), and our depth
perception becomes less acute.

Noise exposure over a lifetime causes
hearing loss: It’s harder to hear higher
pitches, and speech (including high-pitched
sounds such as T, S, and P in
English) is harder to understand. Our
senses of taste and smell become less
acute. And skin becomes thinner, less
elastic, and drier.

The Mayo Clinic notes that our bladders
often become less elastic with age, which
leads to more frequent urination and
potentially a raised risk for incontinence.

But aging isn’t all bad news. In a
2016 study published in the Journal of
Clinical Psychiatry and reported by Time,
researchers at the University of California,
San Diego found that happiness changed
throughout life, and they found a “dipping
down” in middle age.

Then happiness rebounded. Said Time,
“People in their 20s and 30s reported the
highest levels of depression, anxiety and
stress, plus the lowest levels of happiness,
satisfaction and well-being. Older people,
surprisingly, were the happiest.”