As if older men didn't have enough to worry about between
hair loss and high cholesterol, according to a recent report
in the Archives of General Psychiatry, a journal
of the American Medical Association, fathering a child late
in life increases the chances of the offspring having bipolar
The study generated headlines like, "Older Fathers Linked
with Bipolar Disorder," and "Bipolar Risk Rises with Father's
Age." True enough; the study concluded that "the offspring
of men 55 years and older were 1.37 times more likely to be
diagnosed as having bipolar
disorder than the offspring of men aged 20 to 24 years."
A 37 percent percent increase seems important, but in this
study (as in many others rooted in statistics), a few caveats
tend to be overlooked.
First, the increase in incidence of bipolar disorder was
also tied to the mother's age, though not as much. Researchers
believe that the older a man is at fatherhood, the higher
the chance that his sperm may be subjected to damaging mutations.
Women, on the other hand, are born with a limited number of
eggs which are not replicated as they age (and therefore are
less vulnerable to mutation).
More importantly, the 37 percent increase in bipolar disorder
seems very dramatic until you realize that the incidence of
the disorder in the general population is very low to begin
with. According to the National Institute of Mental Health,
about 2.6 percent of adults in any given year can be diagnosed
with bipolar disorder. A 37 percent increase would translate
into about a 3.5 percent chance of a father over age 55 having
a child with bipolar disorder.
Thus in the general population, 97.40 percent of children
will not develop the disorder, and among "old dads"
the number drops to 96.43 percent. Does the difference —
less than one percent — really justify the headline
warnings and caution about fathering a child at an older age?
This is one of those "So What?" studies that are often exaggerated
by journalists who fail to put numbers into context and perspective.
The research is interesting, but really only relevant to doctors
The increase in incidence of bipolar among the offspring
of older fathers may be statistically significant, but it
is not socially significant. It is not information that should
guide behavior, and scary headlines should not deter fathers
from having children later in life if they so choose.