Scientific American - November 2018

66 Scientific American, November 2018

illness, the more stress the women

reported and the shorter their

telomeres were, even after the

researchers accounted for poten-

tially confounding factors such

as diet and smoking. Telo meres

normally shorten at a more or

less constant rate in people, and

calculations showed that these

women’s telomeres had aged

roughly an additional decade—and

sometimes more—past those in

the low-stress group.

This discovery triggered a flood

of supporting studies showing that

stressors that included major de-

pression, post-traumatic stress dis-

order and the experience of racial

discrimination can all accelerate

telo mere shortening. Unsurpris-

ingly, lower childhood SES also

predicts shorter telo meres in

adulthood; perceived poor neigh-

borhood quality, witnessing or

experiencing violence, family in-

stability (such as divorce, death

or incarceration of a parent), and

other features of poor status early

on are tied to these shrunken chro-

mosome tips later in life. Spend

your childhood in poverty, and

by middle age your telo meres

will probably be about a decade

older than those with more fortu-

nate childhoods.

Thus, from the macro level of

entire body systems to the micro

level of individual chromosomes,

poverty finds a way to produce wear

and tear. Most studies of telomere

length compare “poor” with “non-

poor,” as do the studies comparing

allostatic load, but the few studies

that examine the whole spectrum of

inequality, step by low-status step,

show that every rung down the SES

ladder most likely worsens these bi-

ological markers of aging.

OUT OF CONTROL

SLIPPING DOWN these rungs also

changes the brain and behavior, ac-

cording to a slew of recent neuro-

biological studies. My laboratory

has devoted a quarter of a century

to studying what ongoing stress

does to the brain in rodents, mon-

keys and humans. Along with other

labs, we have learned that one hot-

spot is the hippocampus, a region

critical to learning and memory.

Sustained stress or exposure to ex-

cessive glucocorticoids impairs

memory by lowering hippocampal

excitability, retracting connections

between neurons and suppressing

the birth of new neurons. In the

amygdala, a dierent brain area

that is central to fear and anxiety, THE SPIRIT LEVEL: WHY GREATER EQUALITY MAKES SOCIETIES STRONGER.

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4

–1

Low

2

1

0

5 6 7 8

Index of Health and Social Problems

Wo rse

Better

Income Inequality, 2005 (20:20 ratio)

High

Sweden

NorwayNorw

Finland

Denmark

Belgiumelgium

Austria

Germany

i

France

IrelandIre

Greece

Canada

Netherlands

Switzerland

Spain

S

Italy

Australia

New Zealand

U.K.

Por tugal

U.S.

0.4

–1

Low

2

1

0

0.45 0.5

Index of Health and Social Problems

Wo rse

Better

 ́`¹®y ́yÕùD ̈ŸïĂjÀμμμÊŸ ́Ÿ`¹yˆ`Ÿy ́ïË

High

–1

Low

2

1

0

GDP per Capita, 2005 (U.S. dollars, at purchasing power parity)

High

Sweden Norway

Finland

Belgium Denmark

Germany Austria

France

Ireland

Greece

Canada

Netherlands Switzerland

Spain

Italy

Australia

New Zealand

U.K.

Portugal

U.S.

25,000

–1

Low

2

1

0

35,000

25,000 35,000

Per Capita Income, 1999 (dollars)

High

AK

UT

WI

NH

IA

VT

MN

ND

NENE

ID

IN

DE

MD

NV

MI

OHO

WYMECO

OR

HIKS

MTMT

MA

WAWA VA

RINJ

PA

AZ ILIL

MONC

SC SC TN

TX

PA

MI

GA

AK DE

MN

CO NJ CT

MA

IL

NH

CA

WA

NY

MD

RI

FL

HI

WI

NE

OR

WY

NC

IN

MO

OH

ID

IANN

ND VT

0

ARGA AR

NMTN NM

AAKY

TX KY

WVWWWV

OKO FL CA WV OKAZ

SD KS

ME

AL

MS

LA MS

LA

NY

CT UT

MT

VAV

NV

Health and social problems are worse in countries

with more income inequality

U.S. states also show worse health and social problems

as income inequality climbs

U.S. states with higher average incomes rarely

show improved health

Higher average income levels in countries

do not mean better health

Overall trend

Index of Health

and Social Problems

includes these

components:

• Life expectancy

• Teenage births

• Obesity

• Mental health

• Homicides

• Imprisonment

• Trust/mistrust

• Education

• Infant mortality rate

• Social mobility (for

country level only)