Centenarians, defined as people age 100 or older, are a tiny but growing age group in Michigan and the United States as a whole . In the 2010 U.S. Census, centenarians constituted .0173 percent of the U.S. population and a similar proportion (.0175 percent) of Michigan’s population (1,729 centenarians of the total of 9,883,640 people in Michigan). In the first part of this two-part blog series, we looked at this group not by studying living centenarians but by studying the characteristics of Michigan residents aged 100 or older who died from 2011-2013.
In this second part we contrast centenarians’ characteristics with those of Michigan residents who died in 2011-2013 at ages 65-69, 70-79, 80-89, and 90-99. In making this comparison it is important to keep in mind that not all differences are simply a function of increasing age. Cohort differences – those differences due to being part of a group that grew up at a certain time and experienced things in common that shaped their health, outlook, and experiences – also play a role. For example, if there are differences in marital status at death between say, 65-69-year-olds and centenarians, some of this is due to differences in age-related mortality, but some may also be a result of changing norms regarding marriage.
Population of Study
For this study we used the Michigan Department of Health and Human Services’ Vital Statistics and Health Records database of deaths in Michigan. In order to have a sufficiently large number of centenarian deaths for analysis we aggregated 2011-2013 death records. For those three years, there were 271,853 deaths of Michigan residents in total. Of that total, 2,414 were deaths of people 100 years old or older (0.9 percent), and 197,205 were to individuals ages 65-99 (72.5 percent).
Table 1. Number of deaths by age group. Michigan deaths 2011-2013.
In analyzing characteristics of the populations we studied we found missing data on some records. For the analysis of a particular characteristic, records with missing data have been eliminated. As a result, the number of records in some of the analyses is less than the total of 199,619 deaths (197,205 + 2,414).
Characteristics of Centenarian Deaths and Deaths in Age Groups 65-99
In this section we contrast the characteristics of centenarians who died during 2011, 2012, and 2013 with the characteristics of Michigan residents aged 65-69, 70-79- 80-89, and 90-99 who died during the same period. (In Table 1 note the increase in the number of deaths for people in their 80s compared to the number for those in their 70s.)
Figure 1 illustrates the striking change in the percentages of male and female deaths with increasing age.
Figure 1. Percentages of male and female deaths by age group. Michigan deaths 2011-2013.
Table 2. Percentages of White and Black deaths by age group. Michigan deaths 2011-2013.
Comparisons by race are shown only for Blacks and Whites in Table 2. Because the number of 100+ year old Blacks was statistically small (259), the comparison for that age group must be viewed with caution.
The percentage of deaths of Whites (total of 176,038 deaths to ages 65+ 2011-2013) increased through each decade up to age 100 and then decreased slightly to 89% for centenarians. Deaths of Blacks (total of 20,754 deaths from 2011-2013) constituted 16% of the 65-69-year-olds, decreased to 7% for individuals in their 90s, and then increased by 4 percentage points for centenarians. 
Table 3. Percentages of deaths by marital status and age group. Michigan deaths 2011-2013.
The trends evident in Table 3 – both the gradual decrease in the percentage never married and the marked decrease in the percentage of divorced with increasing age – bring to mind two explanations, which are offered here only as incentives to look further into the issue. First, we may be seeing cohort differences in the acceptability of divorce. Second, it may be that marriage, here represented by being widowed as well as being married, confers a longevity advantage.
Table 4. Percentages of deaths by educational attainment (three categories) and age group. Michigan deaths 2011-2013.
However, Table 5 reveals the startling increases in the percentage not continuing their education past 8th grade as age increased. While 5% of 65-69-year-olds had not gone beyond 8th grade, the percentage increased 4-5 points through the 90-99 age group and then jumped 9 percentage points to 28% of centenarians.Table 4 is a three-category aggregation of the eight categories of educational attainment shown in Table 5. As Table 4 demonstrates, the greatest difference lies in the higher percentages of 65-69 and 70-79 year olds who continued their education beyond high school than their older age cohorts. The difference is especially marked for the youngest age group.
Table 5. Percentages of deaths by educational attainment (eight categories) and age group. Michigan deaths 2011-2013
The death certificate includes codes for the underlying cause of death, using the 10th Revision of the International Classification of Diseases codes. Comparing across the age groups, we find notable changes in the underlying cause of death. Table 6, which lists the top five underlying causes for centenarians, shows diseases of the circulatory system increasing in importance as underlying causes of death with advancing age, accounting for half the deaths of centenarians but only about 30% of the 65-to-69-year-olds. In contrast, neoplasms are shown to shrink dramatically in representation, decreasing from 36% among 65-to-69-year-olds to 4% among centenarians. These figures must be viewed with some skepticism, however. 
Underlying cause of death
Table 6. Percentages of deaths by underlying cause and age group. Michigan deaths 2011-2013
Summary of Findings and Concluding Remarks
Based on information from the Michigan death certificate this blog post has offered a glimpse into the ways in which centenarians differed from those who died at ages 65-99 in Michigan in 2011-2013. Summary of Findings and Concluding Remarks
Comparing centenarian deaths to deaths in younger age groups (65-69, 70-79, 80-89, 90-99) we found:
- Female deaths outnumbered male deaths starting with the 80-89 age group (55% to 45%), reaching a peak of 84% to 16% among centenarians
- While two-thirds of 65-69 year-old decedents were married (50%) or widowed (17%), just 7% of centenarians were married and 86% were widowed at their death.
- The percentage of decedents stopping their education at 8th grade or less increased with advancing age groups from 5% of 65-69 year-olds to 19% among those in their 90s and 28% of centenarians.
- The underlying cause of death increased in frequency for diseases of the circulatory system with advancing age while neoplasms decreased in frequency.
Clearly, death certificates can give us some basic demographic information about those who died, but there is so much more that we would like to know – information that might give clues as to why some people live past 100 and others die at much younger ages. For example, how did the age groups differ in the strength of their social ties? Did centenarians differ from younger groups in how they handled stress? How did their incomes differ, or their living arrangements? What is the role of heredity: Did people who died in their 100s come from a line of long-lived relatives? How, if at all, did people who died in their 100s, especially in their “youngest” 100s, differ from people who died in their early to mid-90s and those who died in their late 90s? Is there something markedly different about people who live to age 100 or older?
Finally, what can the “oldest old,” those in their 90s and 100s, tell us about what it takes to live a long and fulfilling life? Can the common threads that emerge from their stories help us all lead healthier, more satisfying lives?
 From 1980 to 2010, the percentage of centenarian in the U.S, population grew from 1.42% to 1.73% according to the U.S. Bureau of the Census official counts. (The Census Bureau cautions that counts of the centenarian population are subject to numerous sources of error) Source: U.S. Census Bureau, 2010 Census Special Reports, Centenarians: 2010, C2010SR-03, U.S. Government Printing Office, Washington, DC, 2012
 An analysis of 2010 Census data showed the same shift in the Black/White proportions from people in their 90s to those in their 100s. The author of the analysis wrote that this shift is likely an issue of data quality since centenarians are the survivors of people who were in their 90s a decade earlier, and thus the racial composition of centenarians in 2010 should reflect the racial composition of nonagenarians in the 2000 Census. Source: Meyer, Julie. Centenarians: 2010, 2010 Census Special Reports. Issued December 2012.
 In an enlightening article about the accuracy of death certificate information, Kathryn Schulz wrote, “The Framingham Heart Study, an ongoing longitudinal study in Massachusetts, found that death certificates overstate coronary-heart disease as a cause of death by as much as twenty-four per cent in the general population and by a far greater percentage in the elderly.” Source: Schulz, Kathryn, “Final Forms.” The New Yorker, April 7, 2014.