Transcript Survivorship Poster.ppt

Gender Differences in Age-Specific Survivorship Between
Rural and Urban Communities in Central Willamette Valley, OR
Grabow, Jessica A., and Scott P. Oeffner
Department of Biology, Western Oregon University
Monmouth, Oregon 97361
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Abstract
We collected demographic data from 3,543 headstones (n = 1,642 rural
headstones, n = 1,901 urban headstones) between urban and rural communities in
the Northern Willamette Valley, Oregon (Table 1). We hypothesized no differences in
survivorship between genders, and those born before and after 1900. Males, both in
urban and rural communities, exhibited significantly lower survivorship than females.
Analyses also revealed differences in (qx), the probability of surviving to a certain age,
between urban and males born both before and after 1900. Most significant
differences were found during mid-life (ages 30 to 50). We conclude that significant
industrial, sociological, and global events during the early 20th Century equally
affected both community types.
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Figure 3.
We found a significant difference between the survivorship curves (age class 14 to
21 (ages 70 to 105)) of males and females (Figure 3). This pattern was true for all
comparisons; urban males versus urban females, rural males versus rural males, and
both before and after 1900. Biological/physiological differences between males and
females are likely the reason for this difference.
1000
Probability of 100
Surviving to
Age Class
(qx)
Males
Females
There was a significant difference between males born before 1900 and males
born after 1900 (Figure 4). Although we did not show the comparison of survivorship
curves between females born before 1900 and females born after 1900, this
comparison showed a significant difference during the age classes 13 to 18 (ages 65
to 90). This was surprising because advances in technology and medicine would
likely have led to increases in survivorship, not decreases. Military conflicts
throughout the 1900’s (WWI and WWII, Korean War, etc.) may have significantly
decreased the ability to survive to greater age classes for those individuals born after
1900. Our future research will investigate this hypothesis.
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(+ 1 S. E.)
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0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
Age Class
Figure 4.
1000
Probability of 100
Surviving to
Age Class
(qx)
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(+ 1 S. E.)
Results and Discussion
There was no significant difference between the survivorship curves comparing
rural males and urban males as well as comparing rural females to urban females
(Figures 5 and 6). However, many of the communities sampled had less
demographic differences than previously assumed. Specifically, both communities
were equally affected by the events (industrial, sociological, and global) that altered
the ability to survive to greater age classes for those individuals born after 1900.
Males Born After 1900
Males Born Before 1900
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0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
Figure 5.
Age Class
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Probability of 100
Surviving to
Age Class
(qx)
Introduction
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
Figure 1. Satellite map of the Willamette Valley,
Oregon showing the 11 sampled
communities in relation to the cities of
Portland and Eugene (Urban indicated
by red pins and Rural indicated by blue
pins).
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Figure 2. Scott P. Oeffner collecting tombstone
data from the Vernonia community
cemetery.
(+ 1 S. E.)
Literature Cited
Hendrick, Philip W. 1984. Population Biology: The Evolution and Ecology of
Populations. 206-213pp. Jones and Bartlett Publishers Inc. Portola Valley,
California.
Neher, Deborah. 2004. Human Demography. 56-67pp. http//www.uvm.edu/~dneher/
biodiversity/10_Demography.pdf. Accessed 19 November 2008
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0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
Age Class
Probability of 100
Surviving to
Age Class
(qx)
(+ 1 S. E.)
If there is a significant difference in the ability to survive to a certain
age between genders?
qx is the probability of surviving to a certain age:

px is age-specific mortality:  px 


lx  1 

lx 
qx  1  px 
lx is the proportion alive at the beginning of each age class (standardized to
populations of 1,000 individuals).
Rural Females
Urban Females
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If the survivorship of urban and rural populations differ significantly?
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0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
Age Class
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Conclusions

We constructed survivorship curves following Hedrick (1984). Specifically, we
plotted qx , the probability of surviving to a specific age class, against time t, where:

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1000
Figure 6.
If there is a significant difference between the population’s ability to survive to
a certain age before 1900 and after 1900?
We collected headstone data from 5 urban populations (Corvallis, Monmouth,
Hillsboro, McMinnville, and Newberg) and 6 rural populations (Vernonia, Banks,
Willamina, Sheridan, Falls City, and Dallas) (Figures 1 and 2). We grouped each
population into males born before 1900, males born after 1900, females born before
1900, and females after 1900. By comparing survivorship curves of different time
periods, historical trends in the demography of each population could be inferred and
link changes to historical events and/or cultural differences, each population’s
environment.
Rural Males
Urban Males
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Demography is the study of the composition of a population over time, and the
effects of that population in terms of growth (Neher 2004). Human population
compositions can be studied by constructing survivorship curves, which are graphical
representations of the probability a certain person will survive from birth to a particular
age (Neher 2004). To assemble survivorship curves, we collected headstone data
(birth, death, age) from eleven populations to try to infer…

1000

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Males, both urban and rural, born before 1900 expressed reduced
survivorship through midlife [age classes 3 to 18 (15 to 90yrs)] when
compared to males born after 1900.
Males and Females born before 1900 lived significantly longer than those
individuals born after 1900 despite medical advancement.
In urban and rural communities, females lived significantly longer than their
male counterparts for both before and after 1900.