JUNE 8 2019 LISTENER 21
drinking three hours or more before
going to sleep, so your digestive system
has done most of its initial work. Most
people suffer sleep deprivation and they
don’t appreciate that means all kinds of
systems in their body are not perform-
ing at peak. It’s nice if you can do 10,000
steps a day, but it doesn’t have as much
benefit as eight hours of restful sleep a
night.”
Smarr has close to 100 different bio-
markers from his blood and stool samples
that provide his personal average over
time – a more valuable measurement
than population-based comparisons. His
various devices measure his blood pressure
100 times a month, his heart rate once a
minute, his sleep every 15 minutes every
night. He freezes stool samples once every
fortnight. His genome has been mapped
three times. This year, he plans to start
measuring his blood for toxin exposure.
The real insight, he says, will come from
examining changes to personal baselines,
which may be the first indicators of
disease.
B
ut what about the risk of over-
diagnosis and overtreatment,
which, according to US American
academic physician H Gilbert Welch –
interviewed by the Listener in 2015 – is
the scourge of modern medicine. In
a story about Smarr in the Atlantic in
2012, Welch, author of Overdiagnosed:
Making People Sick in the Pursuit of Health,
warned those who monitor themselves
as closely as Smarr are pretty much
guaranteed to find something “wrong”.
Abnormality, he says, is normal, and
constant monitoring can lead to unnec-
essary interventions.
Smarr concedes that, given enough
data, you can find a problem, but says
that’s not a bad thing. “You could argue
we overmedicate our cars because we
have things in there that measure the
spark plugs, the fuel injection, the brak-
ing and 100 different variables. When
you take your car in for maintenance,
they read those things out and deter-
mine if any of them aren’t normal. It’s
called preventive maintenance. When
I grew up, you took your car in if you
saw smoke coming out from under the
hood. You want to catch those things
early.”
He believes evidence that fitness track-
ers improve health outcomes will come
with time. The technology is only about
a decade old and population-based
statistics are increasing by the year. In
2018, for example, Fitbit sold 14 mil-
lion devices worldwide, up from 60,000
in 2010. “More and more data about
your body is in your hands; it’s not
in your doctor’s hands,” says Smarr.
“We are very early in the transition
from data-poor knowledge of yourself
to data-rich knowledge. I’m healthier
than I’ve been in 15 years. I’m less
concerned about how long I live, than
that I live as healthy as possible until I
stop living.”
The information doesn’t stress him.
“Stress comes from being in a situation
that you feel you don’t have any control
over. I have much greater knowledge
and therefore control over my health. If
you were driving a car on a busy high-
way at 70 miles an hour and could see
out the windows and mirrors and see
your speedometer ... now put a black
cloth across the windshield and over
your instruments. Which situation is
likely to cause you greater stress?”Larry Smarr:
“Most people
suffer sleep
deprivation.”heart-rate response to exercise has changed.
They already have heart disease and they’ve
come to me and it seems something has
gone wrong or deteriorated.”
He says that’s more useful information
than modest deviations in the “worried
well”. He doesn’t recommend patients use
fitness trackers, because most are not FDA-
approved medical-grade devices. “It may
just cause more anxiety, and I don’t have
confidence in algorithms that are hidden
away in company systems.”
He’s also worried about privacy issues,
the extent of the surveillance of data and
its potential use by insurance companies.
“It’s like when people who go on overseas
holidays are weighed because they’re fatter,which similarly has a degree of yuck about
it. You could get to a very punitive situa-
tion where instead of providing goals and
encouragement, you’re penalising people
and that could make disparity worse.”
But if people want to buy a device, he
wouldn’t stop them. “I didn’t realise how
many steps I took at work until I got my
phone app and then I was horrified. Now I
take the stairs instead of the elevator. In the
weekends I’ll easily make 10,000 steps, but
during the week it’s 2500-3000. As a junior
doctor, I walked 7km a day and wore out a
pair of shoes a year. My shoes don’t wear out
anywhere near as quickly now.”THE APP UPDATE
I still haven’t got to the bottom of my Fit-
bit’s behavioural blip. I tweet-messaged
the company’s support service for help. It
wasn’t the Fitbit, they said. It was me. The
app update hadn’t altered the way heart
rates are measured, and I’d probably just
changed the way I was wearing it. (I hadn’t.
Nor had I changed my routine.) What I have
done, though, is reassess my relationship
with my Fitbit and my dependence on it.
My former lover has now been friend-zoned.
“It’s not you,” I said, “it’s me.” But I didn’t
really believe it. l“I didn’t realise how
many steps I took at work
until I got my phone app
and then I was horrified.Now I take the stairs
instead of the elevator.”