Front Slide

Health & Cycling

Professor Bruce LynnEmeritus Professor of Physiology, UCLHealthy Rides Co-Ordinator, Southwark Cyclistswww.healthyrider.weebly.com

June 3rd, 2014evening lecture series: Cycling for Transport: A Technical, Society-Focussed and Policy

Based Overview

Outline of presentation

• Essential background and some key facts

• Exercise and health: the best arguments

• Cycling and health: evidence base

Physical activity Fitness and good health

We are designed to run!

But remember we have also evolved to be as energy efficient as possible – and ingrained behaviour patterns reflect this.

Our heart, muscles, vascular system are designed for serious levels of physical activity.During hominid evolution survival depended on physical activity for obtaining food, for establishing territory, and so for success in procreation.

But when possible, Stone Age Man needed to rest. And when food was available, they needed to eat enough to lay down storage fat in case of future lack of success in hunting, or a drought.So our brains are programmed appropriately.

When possible be sedentary – rest.When there is food – eat it!

This is the problem in the modern environment

Our body needs to exercise to stay healthy.

But our brain says •Be lazy•And eat enough to ensure you can outlast the next famine

And of course this is why exercise promotion is such a tough business

And the consequence:

Non-communicable disease is now the principle cause of death and chronic illness.

More people die from cardiovascular disease, cancer, stroke and other NCDs then from infectious disease (malaria, cholera, AIDS etc) or from trauma (road collisions, warfare)

How important is exercise?

What about smoking, poor diet, lousy air quality?

Smoking provides about the same risk of early death as low physical fitness. But affects many fewer people – so the population risk is less than half.

High blood pressure also confers about the same risk as sedentary living. But, due to changes in diet and effective medication, now affects many fewer people.

How important is exercise?

What about over-eating - obesity?

Excessive eating – too many calories. Turns out, surprisingly, to be not an issue at all! We probably eat the same number of calories as our neanderthal ancestors.

Secular trends in diet (left) and activity (right) in relation to obesity in Britain.

Prentice A M , Jebb S A BMJ 1995;311:437-439

©1995 by British Medical Journal Publishing Group

Changes in average energy intake in Britain over 60 years.

Prentice A M , Jebb S A BMJ 1995;311:437-439

©1995 by British Medical Journal Publishing Group

6

8

10

12

1986/7 2000/1 2008/10

Year

En

ergy

Inta

ke (

MJ/

day)

Data from UK National Diet and Nutrition Surveys

Energy expenditure at work, kcal

Year

Energy expenditure has been falling

This fall in US energy expenditure is enough to account for the increase in body weight seen over the same period.

This energy needs to be put back into everyday life, e.g. by cycling more

Church TS, et al. (2011) PLoS ONE 6(5): e19657.

How important is exercise?

What about over-eating - obesity?

The reason we get fat is that we do not exercise.

Unscrambling the risk of fatness from the risk of under-exercising is tricky. But much evidence indicates that not exercising is worse for us than being overweight.

0.8

0.9

1

1.1

1.2

1.3

1.4

25-30 30-35 >35

Haz

ard

Rat

io

BMI:

Overweight Grade 1 Obese Grade 2,3 Obese

Association of all-cause mortality with overweight and obesity using standard body mass index categories: a systematic review and meta-analysis. Flegal KM, Kit BK, Orpana H, Graubard BI. JAMA. 2013 Jan 2;309(1):71-82.

Chance of dying relative to normal weight (BMI 18.5-25) individualsOverweight looks best!

This well-researched review provoked a furious response!

Walter Willett from Harvard School of Public Health was interviewed on US National Public Radio. His interview was promoted by the Harvard Media Office and rapidly taken up as a "counter" position to the original study, particularly the soundbite that he provided: that "This study is really a pile of rubbish, and no one should waste their time reading it."

Tam Fry, from the National Obesity Forum in the UK, said: "It's a horrific message to put out at this particular time.”

Prof John Wass, vice-president of the Royal College of Physicians said: "Huge pieces of evidence go against this, countless other studies point in the other direction."

http://newsatjama.jama.com/2013/02/14/jama-forum-separating-the-science-and-politics-of-obesity/

JAMA Forum: Separating the Science and Politics of “Obesity” Filed under: Medicine and the Media,Obesity,The JAMA Forum — news@JAMA @ 10:29 am

By Stacy M. Carter, PhD, MPH, and Helen L. Walls, PhD, MPHThoughtful analysis of why reaction was so fierce.

“Obesity in the sociopolitical sense also became institutionalized fairly rapidly in universities and governments…. There are now obesity strategies, government departments responsible for obesity, obesity handbooks, professorial chairs, university research centers, websites, …. No wonder it has become such a battleground.”

“…it might be time to remove the word obesity from the names of centers, advocacy organizations, university chairs, and so on. If our professional identities are at stake, it is more difficult to remain civil” (in scientific discourse).

“The relation between BMI and health is imperfect. The basic messages of health promotion, however, are fairly consistent. Human health depends on good housing in safe neighborhoods, safe and rewarding employment, fresh and whole food, physical activity, recreation, and social connectedness.”

Exercise gets you fit, usually measured as maximum oxygen consumption, VO2max

Lets look at the relation of fitness to health in more detail.

The fitter you are, the healthier you are.

Steep relation between health measures and measures of fitness or physical activity

BMI and Morbid Obese Trend, All adults, HSE. +/- 1 s.e.

25.6

25.8

26.0

26.2

26.4

26.6

26.8

27.0

27.2

27.4

27.6

1990 1995 2000 2005 2010 2015

Year

BM

I, k

g/m

2

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

% M

orb

id O

be

se

, >4

0 B

MI

BMI

Morb Ob

Poly. (BMI)

BMI trend has flattened.

Big problem is nearly 200% increase in morbidly obese.

Children (age 2-15) BMI trend. HSE. +/- 1 s.e.

17.6

17.8

18.0

18.2

18.4

18.6

18.8

19.0

19.2

1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014

Year

BM

I kg

/m2

Risk of death. Age-adjusted hazard ratios versus exercise capacity and adulthood recreational activity, expressed in quartiles, with the least fit or least active group as the reference group (quartile 1). MET=metabolic equivalent = 3.5 ml O2/min.kg. N=6200. Av age 59. Av follow-up, 7 years. Myers, J. et al Am J Med. 2004;117:912–918

Note, these are huge differences in risk of death.

If you are pretty fit at 60, your chance of dying in the next 7 years is only 25% of someone in the least fit quarter of the population.

And the risks are substantial.

After 6 years 25% of the lowest fitness group were dead. But only 7% of the highest fitness group.

I know which group I want to be in!!

Relative risk of death versus aerobic fitnessData from Kuopio Ischaemic Heart Disease Risk Factor Study. The study population is a representative sample of Finnish men who were 42–60 years of age at baseline examination between 1984 and 1989. 1294 healthy men, median follow up 13.7 yrs

Jari A. Laukkanen et al. European Heart Journal (2004) 25, 1428–1437

Note these are large risksCa 1:20 for most fit; 1:3 for least

How much exercise do we need?

New UK 2011 guidelines:

1. Adults should aim to be active daily. Over a week, activity should add up to at least 150 minutes of moderate intensity activity in bouts of 10 minutes or more. Moderate = up to 11 mph cycling

2. Alternatively, comparable benefits can be achieved through 75 minutes of vigorous intensity activity spread across the week or combinations of moderate and vigorous intensity activity. Vigorous = more than 11 mph cycling

3. Adults should also undertake physical activity to improve muscle strength on at least two days a week. So up some steep hills or a bit of mountain biking!

Children 300 min/wk

But remember this is the level that gets you SOME benefit, not the level that gives you optimal fitness and health

Note how low the guideline is.

150 min/wk is 30 min per working day.

A 15 min ride to work and home again is enough!

Neanderthal man did rather more than this, and in consequence probably had a rather healthier cardiovascular system!

Exercise and health: the best arguments

First, general arguments regarding exercise and health

Children: Health arguments not useful. Key here is independence/enjoymentMaybe can also suggest they will find school work easier.

Martinez-Gomez, D. et al Arch Pediatr Adolesc Med.

Published online December 6, 2010.

Participants: A total of 1700 adolescents (892 girls) aged 13 to 18.5 years.

Cognitive function in adolescents is higher, at least in girls, if you walk or cycle to school

ACS = active commuting to school

Exercise and health: the best arguments

Adults (18-50). Again, stressing risk of early, lingering, death does not work. People still think they are immortal.

Better to stress (health-related) quality of life.

Adult quality of life arguments

Can fully participate in activities involving physical exertion such as dancing, charity runs.

Feel better – less depression etc.

Look better!

Better sex life

0

1

2

3

4

5

Low Mod High

Physical Activity

Od

ds

Ra

tio

(H

igh

re

f)

0

0.5

1

1.5

2

Lo, Lo Lo, Mod/Hi Mod/Hi, Lo Mod/Hi,Mod/Hi

Physical Activity: 1965, 1974

Od

ds

Rat

io, M

H,M

H r

ef

More depressed if NOT activeLongitudinal study in CaliforniaInitial random sample of 8023 recruited in 1965As many as could be found re-examined in 1974 and 1983Symptoms of depression from questionnaireOdds ratio (proportion with symptoms compared with proportion in high activity group).Much more depression in low than high activity groupsChanges in activity levels were a strong indicator of future depression.

1965 Baseline situation

PA changes 1965-74, symptoms in 1983

Camacho, TC et al (1991) Am J Epidemiol, 134, 221-31

Runners have Better Sex •A Sunday Times survey confirmed that runners have better sex; it also showed that runners who have sex the night before the London Marathon do better, on average, than those who do not

•Runners are better lovers, says Dr Michael Cohen•A Harvard study found the sex lives of women and men over 40 who exercised regularly were similar to those of many people in their late 20s and 30s

From the Serpentine Running Club websitehttp://www.serpentine.org.uk/pages/beginners_bettersex.html

But actually the evidence is that all forms of exercise are good for your sex life, not just running.

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

ED pAD

Odd

s R

atio

Sedentary§§

Insufficientactivity††

Sufficientactivity‡‡

§§ No participation in physical activity; †† Some physical activity reported but not meeting ‘sufficient’ criteria; ‡‡ At least five separate sessions of vigorous intensity activity

A representative sample (n = 5990) of Australian men aged 40+ years, stratified by age and State, was contacted by random selection of households, with an individual response rate of 78%. All men participated in a 20-minute computer-assisted telephone interview exploring general and reproductive health.

ED - erectile dysfunction

pAD - response to question:‘Do you think you may currently be suffering from low levels of testosterone now?’

Holden et al. BMC Public Health 2010, 10:96. http://www.biomedcentral.com/1471-2458/10/96

The over 50s

Here the health arguments start to be effective.

We know too many people who have had heart problems.

Some close friends/relatives are developing chronic illnesses.

May be visiting people in nursing homes.

This area is well-researched.

Risk of early death is roughly doubled if you are sedentary

Risk of cardiovascular disease, several common forms of cancer, diabetes and approx 40 other conditions all linked to low physical activity. Typically increased risk of developing a problem is 50-100%.

Are we all too busy to find time for exercise?

"Most people in modern life just don't have the time in our lives to spend several hours a day exercising." Prof Terence Stephenson, Academy of Medical Royal Colleges (AoMRC), launching campaign on rising levels of obesity, 15 April 2012.http://www.aomrc.org.uk/item/medical-profession-united-in-fight-to-defuse-obesity-time-bomb.html

Yet…UK viewers notched up an average of four hours and two minutes a day watching TV in 2011

Cycling and Health: key evidence

Cross sectional – health status of cyclists in one-off surveys

Cohort studies – seeing who dies

Experimental – looking at health effects of starting cycling

020

406080

100120140

160180

0.00 5.00 10.00 15.00 20.00 25.00Time, mins

Hea

rt r

ate,

bpm

Gr Way

/TCR L

ts

Eus R

d/TCR L

ts

Parkw

ay

Prince

W R

d

KT Rd/

Forte

ss R

d jn

Tufne

ll Pk

Archw

ay

Mor

n Cre

sc

Bicycling from Bloomsbury to the Archway CampusHeart rate recordingAt or above the “training zone” for 18 min – big contribution to fitness.

89

90

91

92

93

Low activity High Activity >20% cycling

Av

BP

, mm

Hg

5

5.2

5.4

5.6

5.8

Low activity High Activity >20% cyclingC

ho

lest

ero

l, m

mo

l/l

5.2

5.3

5.4

5.5

5.6

5.7

5.8

5.9

Low activity High Activity >20% cycling

Gly

Hb

, %

Health indicators in cyclists

Low activity < 1 hr/week, N=4743High Activity >= 1 hr/week, N=9772>20% cycling group: High activity where cycling is >20% of all activity, N=536.Data from Health Survey of England, 2008

Cyclists live longerStudy of random sample of 6954 subjects in Copenhagen.Looked at physical activity, smoking, BMI, blood lipids (cholesterol etc), blood pressure.Followed for 15 years.Found usual increased mortality in those with low physical activity, who smoked, had high BP etc.

Looked at those who cycled (or had cycled) to work and those who did not.Concluded: “Those who used the bicycle as transportation to work experienced a lower mortality rate even after adjustment for leisure time physical activity”

“Even after adjustment for other risk factors, including leisure time physical activity, those who did not cycle to work experienced a 39% higher mortality rate than those who did.”

Lars Bo Andersen et al., Arch Intern Med. 2000;160:1621-1628

Reduced Mortality risk for cyclists.

0

0.2

0.4

0.6

0.8

1

1.2

0 min/week 1-59 min/week >=60 min/week

Total cycling, min/week

Haz

ard

Rat

io

EPIC-Norfolk cohort, n=22 450 Adults aged 40–79 years at startAverage follow up 15.3 years. Error bars 95% conf limits.Note sub-group with more detailed cycling data but shorter follow up did not show sig reduced mortality

Sahlqvist S, …, Cavill N, et al. BMJ Open. 2013 Nov 14;3(11):e003797.

26

26.2

26.4

26.6

26.8

27

27.2

27.4

27.6

27.8

28

Start 6 months 12 months

BM

I, kg

.m2

20

22

24

26

28

30

32

34

36

38

40

VO

2m

ax, m

l/kg.

min

BMI

VO2max

From Tjelta et al., Tidsskr Nor Laegeforen (2010) 130, 1246-9

Recruited 25 non-cyclist, non-exercisers. Cycled >5km to and from work for a year. First 6 months, May-Oct, average exercise 200 min/wk; 2nd 6 months, Nov-April, 145 min/wk. Stavanger, Norway. 16 male, 9 female, av age 43±8. Given a free bike!

25% increase in aerobic fitness (VO2max).

Small but significant reduction in BMI

From Tjelta et al., Tidsskr Nor Laegeforen (2010) 130, 1246-9

Recruited 25 non-cyclist, non-exercisers. Cycled >5km to and from work for a year. First 6 months, May-Oct, average exercise 200 min/wk; 2nd 6 months, Nov-April, 145 min. Stavanger, Norway. Given free bike!

Significant fall in total cholesterol.

Marked rise in HDL, the “good” cholesterol

4

4.2

4.4

4.6

4.8

5

5.2

5.4

5.6

5.8

6

Start 12 months

Tot

al c

hole

ster

ol, m

mol

/l

1

1.1

1.2

1.3

1.4

1.5

1.6

1.7

1.8

1.9

2

HD

L ch

oles

tero

l, m

mol

/l

Total cholesterol

HDL cholesterol

40

42

44

46

48

50

52

54

56

Cyclist Non-cyclists

VO

2m

ax

, m

l/m

in.k

g

Before

After

Børrestad et al. (2012) Scand J of Public Health 40: 245–252

Norwegian 10-13 year-olds. Before and after 12 weeks of cycling to school every day. Randomised, controlled, trial. Av distance to school, 1.6 km. N: cyclists, 28; non-cyclists, 18.Note marked increase in fitness in the cyclists.

The risk of physical inactivity compared to road casualties

Source: * **DfT Road Traffic Casualties 2009 *** BHF statistics 2010 edition; McPherson et al 2002.

SourceActive travel briefings for Local AuthoritiesPublic Health England 2013 http://www.noo.org.uk/slide_sets/activity

SUMMARY

•Lack of exercise is a significant risk factor for 40+ diseases and for early death.

•Lack of exercise affects more people than other risk factors such as smoking and high blood pressure

•You do not have to do huge amounts of exercise to get benefits – 30min/day is enough (but more is better!)

•Cycling is an effective form of exercise

•Cycling improves health indices, e.g lowers cholesterol, lowers blood pressure

•For older people, health arguments are powerful

•For younger people, probably most effective to stress quality of life, including sex life!

Cycling, Exercise and Health – Useful sources of information

General Exercise and health

Physical activity to reduce cardiovascular risk. British Heart Foundation. Factfile No 5, Sept 2008. http://www.bhf.org.uk/publications/view-publication.aspx?ps=1000639

Start Active, Stay Active: A report on physical activity from the four home countries’ Chief Medical Officers. Dept of Health, 2011. http://www.dh.gov.uk/prod_consum_dh/groups/dh_digitalassets/documents/digitalasset/dh_128210.pdf

Physical Activity and Health. The evidence explained. A.E.Hardman & D.J.Stensil. Routledge, 2009. 340pp.

Active travel briefings for Local Authorities. Public Health England 2013 http://www.noo.org.uk/slide_sets/activity

Cycling specific

Cycling and Health. What’s the evidence. N.Cavill & A.Davis. 2007. Cycling England. http://www.ecf.com/wp-content/uploads/2011/10/Cycling-and-health-Whats-the-evidence.pdf

Oja P et al (2011) Health benefits of cycling: a systematic review. Scand J Med Sci Sports 21, 496-509

NICE 2012. Walking and cycling guidance. http://publications.nice.org.uk/walking-and-cycling-local-measures-to-promote-walking-and-cycling-as-forms-of-travel-or-recreation-ph41

My web site www.healthyrider.weebly.com has information on cycling and health and on other local campaiging issues