Members of the NBER's Aging Program met March 29 in Cambridge. Research Associate Kathleen M. McGarry of University of California, Los Angeles, and Program Director Jonathan S. Skinner of Dartmouth College organized the meeting. These researchers' papers were presented and discussed:
Péter Hudomiet and Susann Rohwedder, RAND Corporation, and Michael D. Hurd, RAND Corporation and NBER
The Lifetime Risk of Living with Dementia for Six Months, One, Two, or Five Years
Dementia prevalence exceeds 40% at advanced old age, but that high rate is not informative about the lifetime risk of this condition. Yet individuals, policy makers, health care providers, and insurance companies need to know the lifetime risk of dementia and its duration because of the high associated care costs. In this study, Hudomiet, Hurd, and Rohwedder produce nationally representative estimates of the lifetime risk of living with dementia for at least six months, one, two, or five years in the U.S. by gender, race, ethnicity, age at death, health, and socio-economic status. The study sample includes 8,733 individuals who died after reaching age 70 between 1998 and 2014 in a large, longitudinal, nationally representative U.S. survey, the Health and Retirement Study. A subsample has undergone a clinical assessment for dementia (n=856). Using the dementia diagnosis from the subsample, and cognitive, functional status, and health predictors in the larger sample, probabilities of dementia were estimated for the full study sample. Then a longitudinal latent variable model was fit on the wave-by-wave probabilities to estimate the probability of dementia at several discrete times prior to death. The averages of these probabilities provide unbiased estimates of the lifetime risk of living with dementia for these durations or longer. 43.2% of those who died after age 70, had dementia six months before death. 38.6%, 31.7%, and 18.7% had dementia one, two, and five years before death, respectively. The risk was higher for females, the less educated, African Americans, those with lower lifetime earnings, and those who died at older ages. Comorbidities decreased the risk except for stroke and psychiatric problems, which increased it.
Julie Bynum, University of Michigan
The Diagnosis and Prevalence of Alzheimer's Disease and Related Dementias in Clinical Practice
Amitabh Chandra, Harvard University and NBER
Innovation and the Economics of Alzheimer's Disease (discussion talk)
Amanda E. Kowalski, University of Michigan and NBER
Behavior within a Clinical Trial and Implications for Mammography Guidelines (NBER Working Paper No. 25049)
Kowalski examines behavior within a clinical trial to inform treatment guidelines. They use data from the Canadian National Breast Screening Study, an influential clinical trial on mammography. During the active study period of the trial, a substantial fraction of women in the control group received mammograms, and some women in the intervention group did not. Using this mammography behavior, random assignment within the trial, and a standard model from the economics literature, Kowalski divides participants into three groups that differ in how likely they are to receive mammograms. Making comparisons across these groups, two important relationships are found. First, heterogeneous selection into mammography: women more likely to receive mammograms are healthier. This relationship is found using a marginal treatment effect model that assumes no more than the local average treatment effect assumptions. Second, Kowalski finds treatment effect heterogeneity along the margin of selection into mammography: women more likely to receive mammograms are more likely to experience harm from them. This relationship is found using an ancillary assumption that builds on the first empirical relationship. Additional empirical support is found for the ancillary assumption using baseline covariates. These findings contribute to the literature concerned about harms from mammography by demonstrating variation across the margin of selection into mammography. This variation is problematic for current mammography guidelines for women in their 40s because it implies that they unintentionally encourage mammography for healthier women who are more likely to experience harm from them.
Ryan Brown, University of Colorado, Denver, and Duncan Thomas, Duke University and NBER
On the Long Term Effects of the 1918 U.S. Influenza Pandemic
Using the 1918 Spanish influenza pandemic, Almond (2006) concludes that in utero exposure to maternal health insults has a large, negative impact on socio-economic status that reaches well into adulthood. A key assumption underlying this research is that birth cohorts exposed in utero to the influenza are statistically exchangeable with surrounding birth cohorts. The validity of that assumption is investigated using data from the 1920 and 1930 U.S. Censuses. Brown and Thomas document that the exposed cohorts were born to families of lower socio-economic status relative to those who were not exposed. For example, fathers of the 1919 birth cohort were less likely to be literate, worked in lower-earning occupations, had lower socioeconomic status, were older, less likely to be white, had higher fertility and were less likely to be WWI veterans than the fathers of surrounding birth cohorts. Furthermore, after controlling for background characteristics, there is little evidence that individuals born in 1919 have worse socio-economic outcomes in adulthood relative to surrounding birth cohorts.
Simon Jäger, MIT and NBER; Benjamin Schoefer, University of California, Berkeley; and Josef Zweimüller, University of Zurich
Marginal Jobs and Job Surplus: A Test of the Efficiency of Separations (NBER Working Paper No. 25492)
Jäger, Schoefer, and Zweimüller present a sharp test for the efficiency of job separations. First, they document a dramatic increase in the separation rate -- 11.2 pp (28%) over five years -- in response to a quasi-experimental extension of UI benefit duration for older workers. Second, after the abolition of the policy, the "job survivors" in the formerly treated group exhibit exactly the same separation behavior as the control group. Juxtaposed, these facts reject the "Coasean" prediction of efficient separations, whereby the UI extensions should have extracted marginal (low-surplus) jobs and thereby rendered the remaining (high-surplus) jobs more resilient after its abolition. Third, the researchers show that a formal model of predicted efficient separations implies a piece-wise linear function of the actual control group separations beyond the missing mass of marginal matches. A structural estimation reveals point estimates of the share of efficient separations below 4%, with confidence intervals rejecting shares above 13%. Fourth, to characterize the marginal jobs in the data, the researchers extend complier analysis to difference-in- difference settings such as ours. The UI-induced separators stemmed from declining firms, blue-collar jobs, with a high share of sick older workers, and firms more likely to have works councils -- while their wages were similar to program survivors. The evidence is consistent with a "non-Coasean" framework building on wage frictions preventing efficient bargaining, and with formal or informal institutional constraints on selective separations.
Jay Bhattacharya, Stanford University and NBER; Dean R. Lillard, Ohio State University and NBER; and Su H. Shin, University of Alabama
Understanding the Correlation between Alzheimer's Disease Polygenic Risk, Wealth, and the Composition of Wealth Holdings (NBER Working Paper No. 25526)
Bhattacharya, Lillard, and Shin investigate how the genetic risk of developing Alzheimer's Disease (AD) relates to saving behavior. Using nationally representative data from the 1992-2014 Health and Retirement Study (HRS), they find that genetic predisposition for AD correlates with, but is not causally related to older individuals' wealth holdings. People with higher Alzheimer's Disease polygenic risk score (PGS) hold roughly 9 percent more wealth in CDs (hands-off assets) and around 11 percent, 15 percent, and 7 percent less wealth in stocks, IRAs, and other financial assets (hands-on assets) respectively. The researchers explore three hypotheses that could explain these correlations. They hypothesize that people with high risk of AD choose different portfolios because: (i) they know their polygenic risk of developing Alzheimer's Disease and related dementia, (ii) they have lower cognitive capacity, and (iii) the genome-wide association studies (GWAS) process that generated the Alzheimer's Disease PGS failed to fully account for the aging process. The researchers' extended model results do not support the first two hypotheses. Consistent with the third hypothesis, the interaction between age and the Alzheimer's Disease PGS explains the correlation between genetic traits and asset holdings.