African Americans, Hispanics, and longevity

I’ve known for a while that women live longer than men, Hispanic Americans live longer than Euro Americans, and the oldest people in the US are disproportionately black:

At 116 years old, Susannah Mushatt Jones is not only the oldest woman in the US, but also the entire world.

One theory I considered was that higher infant mortality rates in Mexico (I don’t actually know the infant mortality rates in Mexico, this is just an idea,) results in the deaths of premature infants and others with severe health problems, whereas in the US these infants survive for several years–maybe even decades–before dying. The population of Hispanic immigrants, therefore, does not include these children–they’re already gone–but the US population does. This could result in a higher life expectancy among the immigrants than among non-immigrants.

But what about women and blacks? Their infant mortality would be included in the native rates, and even if worse medical care resulted in higher infant mortality among them, this still wouldn’t explain why so many supercentenarians are black.

While researching hippocampi yesterday, I ran across an article about hippocampal volumes in the elderly: Brain Morphology in Older African Americans, Caribbean Hispanics, and Whites From Northern Manhattan

We already know that different people age at different rates, but it appears as well that different races age at different rates, with black brains aging the slowest:

“Results of the regression analysis revealed significant effects of age, sex, vascular disease history, and race/ethnicity on relative brain volume (F_5,685 = 38.290, P < .001). For each additional year in age, there was an associated 0.3% decrease in relative brain volume (β = −0.003, t = 10.34, P < .001) (Figure 2). Relative brain volume among women was 2% larger than that among men (β = 0.02, t = 5.93, P < .001). Hispanic (β = 0.03, t = 7.20, P < .001) and African American (β = 0.02, t = 4.09, P < .001) participants had 2.8% and 1.6% larger relative brain volumes than white subjects, respectively. Finally, for each additional vascular disease, there was a 0.5% associated reduction in relative brain volume (β = −0.005, t = −2.70, P < .001). When interaction terms were entered into the model, none were significant, demonstrating that the association of vascular disease history and age with relative brain volume did not differ across race/ethnicity or sex. Analysis of variance controlling for age and vascular disease history confirmed main effects of sex (F_1,685 = 34.906, P < .001) and race/ethnicity (F_2,685 = 23.528, P < .001) but no sex × race/ethnicity interaction (F_2,685 = 0.167, P =.85) (Figure 3).“

Relative brain volume across racial/ethnic groups and by sex.

relationship among chronologic age, race/ethnicity, and relative brain volume.

 

So why are white males (at least in these samples) aging so quickly?

The Insidious Approach of Death

A friend recently attended their 20th highschool reunion, the sort of event that makes one feel very old. Worse, three of their classmates have already died.

I thought that sounded way statistically unlikely, especially given the group’s demographics, but I ran the numbers, and it turns out that it’s only a little unlikely. Given the small N, we’re probably talking about random chance making the class unlucky rather than a particular propensity for death, but it’s unfortunate either way.

Highschool reunions are also a great (by which I mean depressing) opportunity to see who has aged the most. Some classmates look hardly older than the last time you saw them, while others look like they got hit by a semi full of old. Hopefully not you, of course.

In “Quantification of biological aging in young adults,” Belsky et al confirm what I’ve long suspected: that different people age at radically different rates, not just emotionally/mentally, but also biologically.

From the abstract: “We studied aging in 954 young humans, the Dunedin Study birth cohort, tracking multiple biomarkers across three time points spanning their third and fourth decades of life. We developed and validated two methods by which aging can be measured in young adults, one cross-sectional and one longitudinal. Our longitudinal measure allows quantification of the pace of coordinated physiological deterioration across multiple organ systems (e.g., pulmonary, periodontal, cardiovascular, renal, hepatic, and immune function). We applied these methods to assess biological aging in young humans who had not yet developed age-related diseases. Young individuals of the same chronological age varied in their “biological aging” (declining integrity of multiple organ systems). Already, before midlife, individuals who were aging more rapidly were less physically able, showed cognitive decline and brain aging, self-reported worse health, and looked older.” (bold mine.)

” We scaled the Pace of Aging so that the central tendency in the cohort indicates 1 y of physiological change for every one chronological year. On this scale, cohort members ranged in their Pace of Aging from near 0 y of physiological change per chronological year to nearly 3 y of physiological change per chronological year.”

“Study members with advanced Biological Age performed less well on objective tests of
physical functioning at age 38 than biologically younger peers (Fig. 5). They had more difficulty with balance and motor tests (for unipedal stance test of balance, r = −0.22, P < 0.001; for grooved pegboard test of fine motor coordination, r = −0.13, P < 0.001), and they were not as strong (grip strength test, r = −0.19, P < 0.001).”

“Study members with older Biological Ages had poorer cognitive functioning at midlife (r = −0.17, P < 0.001). Moreover, this difference in cognitive functioning reflected actual cognitive decline over the
years. When we compared age-38 IQ test scores to baseline test scores from childhood, study members with older Biological Age showed a decline in cognitive performance net of their baseline
level (r = −0.09, P = 0.010).”

“Neurologists have also begun to use high-resolution 2D photographs of the retina to evaluate age-related loss of integrity of blood vessels within the brain. Retinal and cerebral small vessels
share embryological origin and physiological features, making retinal vasculature a noninvasive indicator of the state of the brain’s microvasculature (32). Retinal microvascular abnormalities are associated with age-related brain pathology, including stroke and dementia (33–35) … study members with advanced Biological Age had older retinal vessels (narrower arterioles, r = −0.20, P < 0.001; wider venules, r = 0.17, P < 0.001).”

“… these biologically older study members were perceived to be older by independent observers.”

“Based on Pace of Aging analysis, we estimate that roughly 1/2 of the difference in Biological Age
observed at chronological age 38 had accumulated over the past 12 y.”

“… our analysis was limited to a single cohort, and one that lacked ethnic minority populations. Replication in other cohorts is needed, in particular in samples including sufficient numbers of ethnic minority individuals to test the “weathering hypothesis” that the stresses of ethnic minority status accelerate aging.”

“Three Dunedin Study members had Pace of Aging less than zero, appearing to grow physiologically younger during their thirties.”

While I suspect measurement error is at play, I’d still like to know what those guys did.