Spatial Clustering of Scleroderma in Three Michigan

Counties“The Toledo Twins”

Sharon HensleyAlford

Sarah Ann Cleveland

Background

The disease that “turns people to stone”– Chronic, connective tissue disease– Unknown cause– Collagen accumulation in some organs

Classifications– Localized– Systemic

Who has scleroderma

• Approximately 150,000 people in the United States

• 4 times more women than men

Symptoms May Include

• Raynaud’s Phenomenon

• Swelling of hands and feet

• Pain and stiffness of joints

• Thickening of the skin

• Kidney, heart, and lung involvement

• Oral, facial, and dental problems

Diagnosis

• Difficult

• Involvement of several specialists

• May take months to years

Rates in Study Area

Prevalence

• 242 cases per 1million adults

Incidence

• 19 new cases per 1 million adults per year

Reference: Prevalence, incidence and survival rates of systemic sclerosis in the Detroit metropolitan area. Mayes et al.

Age Distribution of Cases

Age Distribution of Scleroderma

0

2

4

6

8

10

1 6 11 16 21 26 31 36 41 46 51 56 61 66 71 76 81 86

Age

Num

ber

of C

ases

Sex Distribution

• 134 Females• 37 Males

• 3.62 times more females than males

78%

22%

020406080100120140160

Males Females

Num

ber o

f Cas

es

Etiologies

• UNKNOWN

• Possibilities include:– silica dust– vinyl chloride monomer– pet ownership– some solvents– appetite suppressants

Significance

To Explore...

• Environmental associations

• Spatial pattern Disease process

Materials

Disease Data– Incidence data for

1989-1991 (N=171)

– Three counties:• Macomb

• Oakland

• Wayne

Population Data– 1990 Census data

– Block and Tract divisions

Methods

• Gathering population data– Finding census data– Extract pertinent information

• Geocoding cases– ArcView Batch Match– Digitizing unmatched cases

Working with Unmatched Cases

• Verifying address: US Post: www.usps.gov

• Using web map programs– Mapquest: www.mapquest.com

• gives county lines

– Vicinity: www.mablast.com

• Digitizing

Matching Rate

171 Original

5 Unmatchable Addresses

n=166

Batch-Matched Addresses

n=148

Non-matched

n=18

Digitized

n=13

Unable to Digitize

n=5161 Matched/166 Total

96% Matching Rate

Statistical Analysis

Null Hypothesis: No spatial clustering

Alter. Hypothesis: Spatial clustering

Test statistic: Ipop, Moran’s I

Statistical Program: STAT!

Macomb/Tracts

Assumption R

Variance : 0.0000000

z-score : -0.3175953

Significance : 0.7507920 (2-tailed)

Approximation

Variance : 0.0000000

z-score : -0.3121641

Significance : 0.7549158 (2-tailed)

Simulation

Significance : 0.8800000 (2-tailed)

STAT Output 4/13/1999

Results from Ipop test

Number of runs : 99

Ipop calculations

Areas (m) : 194

cases (n) : 30

Population (x) : 724110

Ipop : -0.0000099

Ipop' : -0.2377846

E[I] : -0.0000014

% within : 99.9752702

% among : 0.0247298

Macomb/BlockSTAT Output 4/14/1999

Results from Ipop test

Number of runs : 99

Ipop calculations

Areas (m) : 661

cases (n) : 30

Population (x) : 724112

Ipop : -0.0000208

Ipop' : -0.5008514

E[I] : -0.0000014

% within : 99.9957345

% among : 0.0042655

Assumption R

Variance : 0.0000000

z-score : -0.3930764

Significance : 0.6942630 (2-tailed)

Approximation

Variance : 0.0000000

z-score : -0.3855452

Significance : 0.6998335 (2-tailed)

Simulation

Significance : 0.6400000 (2-tailed)

Oakland/TractsSTAT Output 4/13/1999

Results from Ipop test

Number of runs : 99

Ipop calculations

Population (x) : 1101540

Ipop : 0.0000033

Ipop' : 0.0817093

E[I] : -0.0000009

% within : 99.8772695

% among : 0.1227305

Assumption R

Variance : 0.0000000

z-score : 0.2045747

Significance : 0.8379044 (2-tailed)

Approximation

Variance : 0.0000000

z-score : 0.2022084

Significance : 0.8397538 (2-tailed)

Simulation

Significance : 0.5600000 (2-tailed)

Oakland/Blocks

Wayne/TractsSTAT Output 4/13/1999

Results from Ipop test

Number of runs : 99

Ipop calculations

Areas (m) : 632

cases (n) : 86

Population (x) : 2159815

Ipop : -0.0000062

Ipop' : -0.1565116

E[I] : -0.0000005

% within : 100.4700628

% among : -0.4700628

Assumption R

Variance : 0.0000000

z-score : -0.3578355

Significance : 0.7204664 (2-tailed)

Approximation

Variance : 0.0000000

z-score : -0.3542334

Significance : 0.7231640 (2-tailed)

Simulation

Significance : 0.9200000 (2-tailed)

Wayne/Blocks

Discussion

Limitations of Analysis– Position uncertainty– Residential history– Reliability of census data

Future Analysis– Stratification by age, sex, race– 3 county combination analysis– Space/Time Analysis

Thank You

First Honors: Andy Long

Mark Wilson

Dr. Mayes

Geoff Jacquez