Health Numeracy: Explaining risk in numbers patients can use

Kirtly Parker Jones MD

Learning Objectives

• List three different numerical means of presenting risk

• Describe three graphical methods of presenting risk

• Identify at least 3 factors that influence patients’ perceptions of risk

Disclosures

• This presentation has been created in part by the Association of Reproductive Health Professionals (ARHP – to see more you can go to arhp.org and go to CORE slide set)

• I like arithmetic

Arithmetic

• Two plus Three equals?• If there was a 50% decrease in the number

of people who answered the question incorrectly, what would be the subsequent percent of people who answered the question correctly?

Weather Class…..

• If there is a 50% chance of rain today and a 50% chance of rain tomorrow…..

• What is the chance that it will rain today AND tomorrow?

• What is the chance that it will rain today OR tomorrow?

What do oncologists tell patients?

• The 5 year survival of stage 4 ovarian cancer is 12%

• Aggressive chemotherapy can increase the 5 year survival of ovarian cancer by 50%

• What is the chance if surviving stage 4 ovarian cancer for 5 years if a patient undergoes aggressive chemotherapy?

• What do you think the patient hears?

Know your numbers

Expressing Risk

Hennekens CH. Epidemiology in Medicine. 1987.

CausalityWeigh

pros and cons

Degree towhich

attributable

Risk Calculations

Grimes DA. Lancet. 2002.

• An association does not always mean exposure caused outcome

• It could be due to random chance or bias

Associations vs. Causality

Commonly Used Risk Calculations

Absolute Risk

Attributable Risk

Relative Risk

New York Academy of Medicine. 2005. Misselbrook D. Fam Practice. 2002.

The percentage of people in a group who experience a discrete event

Number of events experienced

Total exposure timeof people at risk

Absolute Risk

Of 100,000 women on third-generation OCs, 30 will develop venous thromboembolism (VTE) per year.

Absolute risk

30 per 100,000 woman-years

Mills A. Hum Reprod. 1997.Bromham D, O’Brien T. 1995.

Example of Absolute Risk

BMJ Collections. 2007.

• The difference in risk between those exposed and those not exposed

• Reflects extra risk associated with exposure

Attributable Risk

Risk in unexposed

Risk in exposed

–

=

Risk of cancerin smokers:

100 per 100,000

Attributablerisk:

90 more cancersper 100,000

Risk of cancerin nonsmokers:

10 per 100,000

Attributable Risk: Example 1

Risk from3rd-generation OCs

30 VTE per 100,000 woman-years

Risk from2nd-generation OCs

15 VTE per 100,000 woman-years

–

=Attributable Risk:

15 more VTE per 100,000 woman-years

Attributable Risk: Example 2

Frequency of the outcome in the exposed group divided by the frequency of the outcome in the unexposed group

Grimes DA. Lancet. 2002. Hennekens CH. Epidemiology in Medicine. 1987.

FrequencyExposed

FrequencyUnexposed

Relative Risk

Relative Risk > 1

Increased risk in exposed group

Relative Risk < 1

Decreased risk in exposed group

Hennekens CH. Epidemiology in Medicine. 1987.

Compared with unexposed group:

Interpreting Relative Risk

Relative Risk = 1

No increased risk in exposed group

Absolute Risk:3rd-Generation OCs

30 per 100,000 woman-years

Absolute Risk:2nd-Generation OCs

15 per 100,000 woman-years

Mills A. Hum Reprod. 1997.

=Relative Risk:

2

Relative Risk: Example 1

Relative risk = 20 10 = 2

Risk of cesarean delivery with elective induction of labor 20%

Risk of cesarean delivery with spontaneous onset of labor 10%

Relative risk with induction: 20% 10%

Grimes DA. Lancet. 2002.

more…

Relative Risk: Example 2

= 0.5

Risk of infection after cesarean delivery with prophylactic antibiotics 6%

Risk without prophylactic antibiotics: 12%

Relative risk: 6% 12%

Relative risk = 6 12 = 0.5

Grimes DA. Lancet. 2002.

more…

Relative Risk: Example 3

Ridiculous Relative Risk

Chance of getting heads is 1:2 with a normal penny

In two headed penny, the chance is 2:2

Relative risk is 2

But…..you are always going to get head

Relative risk isn’t useful without absolute risk

Know how to communicate numbers

Communicating About Risk

Try different ways to explain numerical data:

Gigerenzer G, Edwards A. BMJ. 2003.

more…

“Three of every 10 women develop nausea.”

“You have a 30% chance of having nausea.”

Tools: Numerical Data

Avoid shifting denominators in proportions:

Gigerenzer G, Edwards A. BMJ. 2003. Grimes DA, Snively GR. Obstet Gynecol. 1999.

more…

“Headache developed in 3 of every 1,000 women.”

“Headache developed in1 of every 333 women.”

Tools: Numerical Data (continued)

Use absolute risk:

Gigerenzer G, Edwards A. BMJ. 2003. Farley TMM, Collins J, Schlesselman JJ. Contraception. 1998. Sloman SA. Organizational Behavior and Human Decision Processes. 2003.

“Heart attacks occur in

4.2 of every 1 million OC users and 1.7 of every 1 million nonusers.”

“OC use increases the risk of heart attack 2.5-fold.”

Tools: Numerical Data (continued)

Risk level

Calman KC. BMJ. 1996. Berry DC, et al. Drug Saf. 2003.

High <1 in 100

Moderate 1–10 in 1,000

Low 1–10 in 10,000

Very low 1–10 in 100,000

Minimal 1–10 in 1 million

Tools: Descriptive Terms

But your patient needs to know the numbers, too

Annual risk of death (per 100,000)

Bennett P. In: Risk Communication and Public Health. 1999; Chang J, et al. MMWR. 2003. Harvard Center for Risk Analysis. 2006’ Schwingl PJ, et al. Am J Obstet Gynecol. 1999. Trussell J, Jordan B. Contraception. 2006.

Skydiving 100

Driving 20

Pregnancy 11.5

Riding a bicycle 0.8

Airplane crash 0.4

Using OCs* 0.06 *Nonsmoker, age 15–34

Tools: Risk Comparisons

Shulman LP. J Reprod Med. 2003. Chang J. In: Surveillance Summaries. 2003.

Inci

denc

e of

VT

E p

er

100,

000

wom

an-y

ears

0

20

40

60

Pregnancy High-dose OC

Low-dose OC

General Population

Comparative Risks of VTE

• Categories table• Numbers and categories table• Paling Perspective Scale• Paling Palette

Tools: Diagrams

More Effective* Effective† Less Effective‡

Sterilization (male & female)

Birth control pills (combined & mini pill)

Barrier methods

Implants Spermicide

Hormone shot Natural methods

Intrauterine device (hormonal)

Intrauterine device (copper)

Typical Success Rate

Adapted from Steiner MJ, et al. Obstet Gynecol. 2003.

Tools: Categories

Typical Success Rate Typical Pregnancy Rate

Lowest Expected Pregnancy Rate

More Effective*

Sterilization (male & female) 0.5–0.15% 0.5–0.1%

Implants 0.05% 0.05%

Hormone shot 3% 0.3%

Intrauterine device (hormonal) 0.2% 0.2%

Intrauterine device (copper) 0.8% 0.6%

Effective†

Birth control pills (combined & mini pill)

8% 0.3%

Less Effective‡

Barrier methods 15–16% 2–6%

Spermicide 29% 18%

Natural methods 25% 3–5%

Steiner MJ, et al. Obstet Gynecol. 2003.Trussell J, et al. Ardent Media, 2007.

Tools: Numbers and Categories

Steiner MJ. Obstet Gynecol. 2003.

Teaching Methods Affect Knowledge

14%

20%

15%

29%

27%

37%

Pill vs.Condom

HormoneShot vs. Pill

Categories Numbers & categories (WHO) Numbers FDA

Tools: Paling Perspective Scale

INCREASED RISKRisk of death from vaccination

Risk of smallpox

Death from smallpoxif not vaccinated post-exposure

Death fromsmallpoxif vaccinated post-exposure

1 in 2 million

1 in 100 million (or less)

1 in 1.7 billion

1 in 100 billion

Paling J. BMJ. 2003.

Tools: Paling Palette1,000 Women

Paling J. BMJ. 2003.http://www.riskcomm.com/palettes.php

Absolute Risk of Breast Cancer in the General Population

• Each 50-year-old woman has approximately a 2.8% chance of developing breast cancer by age 60 years

• This translates to an absolute risk of 2.8 per 100 women

All Women Aged 50 Years in the General Population—Risk for Breast Cancer by Age 60 Years

All Women Aged 50 Years in the General Population—Risk for Breast Cancer by Age 60 Years

In 100 women, 2.8 are at riskIn 100 women, 2.8 are at riskAmerican Cancer Society, Surveillance Research, 2001. Breast Cancer Facts and Figures 2001–2002. Available at: http//www.cancer.org/downloads/STT/BrCaFF2001.pdf.

Absolute Risk of Breast Cancer After 5 Years of HT

• WHI results indicate an HR for breast cancer of 1.26 after 5 years of HT use (a 26% increase in risk)1

• This translates into an absolute risk of 3.5 per 100 users

Risk of Breast Cancer by Age 60 Years After 5 Years of HT Use (Assuming a 26% Increase in Risk)

Risk of Breast Cancer by Age 60 Years After 5 Years of HT Use (Assuming a 26% Increase in Risk)

1Writing Group for the Women’s Health Initiative Investigators. JAMA. 2002;288:321-33.1Writing Group for the Women’s Health Initiative Investigators. JAMA. 2002;288:321-33.

3.5 of 100 women who are HRT users are at risk (<1 additional woman over baseline risk)

3.5 of 100 women who are HRT users are at risk (<1 additional woman over baseline risk)

Least Effective

Most Effective≤1

pregnancy per 100

women in1 year

Adapted from World Health Organization, 2006.

~30pregnancies

per 100women in

1 year

Implants, female sterilization, vasectomy, IUD

Injectables, lactational amenorrhea method, pills, patch, vaginal ring

Male condom, female condom, diaphragm, sponge, fertility awareness–based methods

Withdrawal, spermicides

WHO Decision Aid on Contraceptive Effectiveness

• Given only effectiveness category information, women overestimated pregnancy risk

• When later shown percentage tables, majority reported rate accurately

• Authors recommend category tools with general range of risk shown within each category

Steiner MJ. Obstet Gynecol. 2003.

Communicating Contraceptive Effectiveness

Farley TMM, Collins J, Schlesselman JJ. Contraception 1998.

10

22

123

Smoker OC User

6

22

7

Smoker OC User

BP Checked

3

Deaths per million woman-years among women age 30–34

Cardiovascular Adverse Events:Screening for Risk Factors

Venous thromboembolismIshemic strokeHemorrhagic strokeMyocardial infarction

Medical student attitudes toward the doctor–patient relationship

Medical EducationVolume 36, Issue 6, pages 568-574, 31 MAY 2002 DOI: 10.1046/j.1365-2923.2002.01233.xhttp://onlinelibrary.wiley.com/doi/10.1046/j.1365-2923.2002.01233.x/full#f1

Attitudes re: patient centered care through medical school

First Third Fourth0

10

20

30

40

50

60

70

80

90

100

TotalMalefemale

Overall correct response rate as a function of numeracy and graphical format.

Hamstra D A et al. Med Decis Making 2014;35:27-36

• Understand risk and how to communicate it• Ensure a trusting environment conducive

to conversation• Put risks in context• Remember cultural, literacy, and

developmental issues • Remember that discussing risk may make it

salient

Pro Choice Public Education Project. 2004.

more…

Guidance

• When providing information about risk, discuss risk reduction

• Remember to present absolute risk • Use different forms of numerical data to

explain risk• Be aware of framing effects• Use risk comparisons with care• Have multiple, complementary tools available

Pro Choice Public Education Project. 2004.

Guidance (continued)

Know Yourself and Your Patient

O’Connor A, Legare F, Stacey D. BMJ. 2003.

Clarify situation

Provide information

Clarify patient’s values

Screen for implementation problems

Decision Aid for Risk Communication

• A misperception of risks may unnecessarily limit choices

• Risk perception is affected by a number of factors

• Clinicians should consider relevant factors and expert guidance about risk communication

• Several tools are available to aid risk communication

What to ask: Patient needs & concerns

What to consider: Relevant factors

What to use: Tools

What to do: Provide guidance

Communicating Risk: How-To’s

“How important is it to avoid pregnancy right now?”

“Do you want (or need) your use of contraception to be private?”

“Do you have concerns about a particular contraceptive?”

“What side effects are you willing to accept?”

“Are you comfortable with methods that require insertion in the vagina?”

Patient Needs & Concerns

“…Decisions about risk are not technical, but value decisions.”

Baker B. In: Risk Communication and Public Health. 1999.

Risk & Health Decisions

Mammography numbers

• For every 2,000 women age 50 to 70 who are screened for 10 years, one woman will be saved from dying of breast cancer,

• 10 will have their lives disrupted unnecessarily by overtreatment.

Nordic Cochrane Center Collaborative, 2006

Mammography Numbers

• repeated screening starting at age 50 saves about 1.8 (overall range, 0.9–2.7) lives over 15 years for every 1000 women screened.

Keen JD. BMC Medical Informatics and Decision Making 2009

Grimes DA. In: Oral Contraceptives and Breast Cancer. 1989.

Widespread dispersion of reproductive

health information

Misperception of

contraceptive risks

+ –Media Influence

Perception & Interpretation of Risk

Individual Risk Presentation

Characteristics of the Risk

People worry more about risks that:• The individual cannot control• Are involuntary• Are associated with particular dread• Are novel or unfamiliar• Result from man-made sources• Are more easily recalled

Harvard Center for Risk Statistics. 2003. Bennett P. In: Risk Communication and Public Health. 1999.

Characteristics of the Risk

Burkman R. Am J Obstet Gynecol. 2004.

Weighing the Risks & Benefits

• Understand risk and how to communicate it• Establish a trusting environment conducive

to conversation• Put risks in context• Remember cultural, literacy, social, and

developmental issues • Remember that discussing risk may make it

salient

Lipkus IM. Med Decis Making. 2007. Pro Choice Public Education Project. 2004.

more…

Guidance for Risk Communication

• When providing information about risk, discuss risk reduction

• Remember to present absolute risk • Use numeric, verbal, and visual formats to

convey health risk• Be aware of framing effects• Use risk comparisons with care• Have multiple, complementary tools available

Lipkus IM. Med Decis Making. 2007. Pro Choice Public Education Project. 2004.

Guidance for Risk Communication (cont’d)

Using numbers your patient can use

• Know your numbers• Know how to present your numbers• Know your patient