My sister Molly – my older sister Molly – recently sent me some an excerpt from Lynne M. Spreen’s blog with some encouraging news about aging.

“According to the Seattle Longitudinal study, our brains are awesome after forty. Seattle tracked the same 6000 people for forty years, finding that people reached their highest cognitive ability from age forty through seventy. This was in four of six areas: vocabulary, verbal memory, spatial orientation and inductive reasoning.”

“[A] substance called myelin, the fatty outer coating of the trillions of nerve fibers in the brain… acts like insulation on a wire and makes the connections work… [T]he development of myelin in the brain area relating to language peaks from the 50s to the 60s (2001, Bartzokis). The insulation allows the neuron to recover faster after signals have been sent and get ready to send the next signal more quickly, giving brain cells what Bartzokis calls greater bandwidth. ‘As myelin increases, it builds connections that help us make sense of our surroundings.'”

All good!

But the evidence sure runs the other direction when you’re talking about tennis. Without a doubt, and especially from the standpoint of winning and losing at the highest level of competitive tennis, tennis is a game where youth matters. Once a tennis player approaches full physical strength and sufficient competitive experience –  late teens for women, early 20s for men – age asserts itself in every match up. And it’s astonishing how small the window of significance is: assuming that both players have reached the age of maturity described in the previous sentence, there is equivalence only between players born within about three years of each other.  With an age gap of four years or more, the younger player has a pronounced advantage.

This is well accepted as a general rule of thumb, but is often and curiously forgotten when it comes to superstars. My admiration for Roger Federer gets tested – and I get testy – when someone tries to diminish his accomplishments by pointing out his losing record (10-23) against Rafael Nadal.

There is almost a five year age difference between the two: Nadal was born on June 3, 1986, Federer on August 8, 1981. During the decade from 2001 to 2011, when Roger was age 20 to 30 (presumably the most-likely “best decade” for a professional male tennis player), his record against players born from 1979-1984 who ranked 1-5 in ATP rankings was an astonishing 131-24. Federer’s record during the same period against those ranked 1-5 in the ATP rankings born four years or more after him was 52-54.  (If you remove his losing record against Nadal it’s 42-31 against the same cohort.)

We all tend to resent the aging process because it’s so heartless. Ask Rafael Nadal, aging (in tennis terms) at the ripe old age of 28.  Nadal has lost in the early rounds of two recent clay court tournaments in which he had been well nigh invincible for the last eight years.

But today I’ve learned that those of us on the sidelines of competitive sports under the age of 70 are expert at talking about such diminishing capacities.  That’s good, I think – though I’d still love to experience 20 year-old legs again.