Cluster Phenotypes - Background• Phenotypes such as “asthma” are difficult to define,

variable over time and/or are subject to recall bias and are “syndromic”.

• Subtypes of asthma are known to exist -– Eosinophilic, neutrophilic, paucigranulocytic, atopic,

occupational.• There are intermediate phenotypes –

– IgE, atopy, AHR, FEV1, eNO• Phenotypes do not “capture” “asthma”

• Ho: Clusters will capture phenotypes that more strongly associate with genetic variation than “asthma”

Cluster Phenotypes

• Cluster Analysis (SAS)• Busselton Health Survey 2005-7• All adults with:

– Age, Sex, FEV1, FVC, eNO, eosinophil count, BMI, airway hyper-responsiveness (AHR), atopy (skin tests)

• n = 1,970• 7 clusters (each with n > 100)

Cluster Phenotypes

Cluster nDoctor-diagnosed

Hay Fever (%)Doctor-diagnosed

Asthma (%)

1 106 52.8 31.1

2 226 28.8 17.7

3 215 45.6 40.0

4 391 42.2 18.2

5 127 31.5 24.4

6 441 31.1 15.6

7 464 20.2 5.4

Cluster Phenotypes

Cluster n Cluster Variables Outcome Variables “Descriptors”

1 106 High eNO, high eosinophils, low BHR, high atopy

Smoke low, HF high, asthma

Allergic sneezing, wheezing twitchers

2 226 Females, obese, no AHR, low atopy Fat Freewheelers

3 215 Reduced lung function, all AHR, moderate atopy High asthma Chronic wheezers

4 391 Males, no AHR, very atopic HF Blotchy blokes

5 127 Males, poor lung function, no AHR Smoke high Puffing Old Blokes

6 441 Younger females, no AHR, low eNO, low eosinophils, low atopy

Smoke low, asthma low Sanctimonious shielas

7 464 Older, good lung function, no AHR, low atopy

Smoke low, HF low, asthma very low

Survivors

Cluster Phenotypes - Questions

• How many clusters?– ? Sub-clusters

• What other variables to collect?• Include exposure?• Include questionnaire data?• Include treatment?• Do clusters suggest pathways?• Best gene association strategy

– GWAS, candidate (from lit. or pathways)?

Cluster Phenotypes

Cluster n Age Sex (%F) FEVPPR FEVFVC eNO EOSIN BMI AHR ATOPY

1 106 49.2 41.5 97.7 76.9 60.0 5.8 25.7 19.8 81.1

2 226 53.9 78.3 92.8 80.9 16.1 3.2 34.5 0.0 30.5

3 215 53.3 56.7 88.2 74.0 23.6 3.9 26.9 100.0 71.2

4 391 51.6 16.9 97.3 77.8 20.7 4.1 27.3 0.0 95.4

5 127 69.4 24.4 68.4 58.3 20.4 3.8 26.4 0.1 49.6

6 441 38.7 80.8 100.9 81.7 14.6 2.7 24.0 0.0 45.1

7 464 68.2 43.3 104.0 77.0 18.3 3.0 26.2 0.0 5.2

Excessive Airway Narrowing in a General Population

n = 201

James et al. ARRD 1992;146:895-9

Airway Compartments

Lumen area

Smooth muscle

Inner wall area

Outer wall area

Basement membrane perimeter

Excessive Airway Narrowing

Airway smooth muscle in asthma: collaborative study

James et al AJRCCM (rejected), Thorax (rejected), ERJ (submitted)

Decline in lung function - the Busselton Health Study

Females

James et al AJRCCM 2005;171:109

Sears M et al. N Engl J Med 2003;349:1414-1422

FEV1/FVC Mean (SE) from 9-26 Yrs in Males and Females, by Pattern of Wheezing

A Longitudinal Study of Childhood Asthma Followed to Adulthood

Asthma (ever)

(p <0.001)*

(p <0.001)*

(p <0.001)*

(p <0.001)*

*1981 vs 2005/07

Q. “Have you ever had asthma?” Q. “Has a doctor ever told you that you had asthma?”

Current Asthma(AHR + recent wheeze)

Wheeze (ever)

(p <0.001)*

(p <0.029)*

(p <0.001)*

Q. “Has your chest sounded wheezy on most days or nights?”

Q. “Has your chest ever made a wheezing or whistling

sound ?”

*1981 vs 2005/07

Recent WheezeWheeze <12 months

Shortness of Breath

Cough/Phlegm

(p <0.02)*

(p <0.02)*

(p <0.02)*

(p <0.02)*

*1981 vs 2005

Smoking

Bronchitis

Q. “Have you ever had bronchitis? Q. “Has your doctor ever told that you had bronchitis?”