Academic journal article Demographic Research

Human Biodemography: Some Challenges and Possibilities for Aging Research1

Academic journal article Demographic Research

Human Biodemography: Some Challenges and Possibilities for Aging Research1

Article excerpt

Abstract

This opinion report - in a series on the future of biodemography - focuses on promising areas that I think will be valuable to develop in the future in order to get a better understanding of the determinants of the health and well-being of elderly people. I discuss two major themes:

i) the benefits of strengthening the ties between biodemography and medical-clinical disciplines to better understand the link between functioning/diseases/vulnerability and mortality,

ii) the male-female health-survival paradox (i.e., males report better health than females, but encounter higher mortality at all ages), and how this paradox may shed light on fundamental aging processes.

1. Introduction

The purpose of this opinion report on the future of biodemography is to outline what I consider to be promising areas of human biodemographic research that could lead to a better understanding of the determinants of the health and well-being of elderly people.

2. Strengthening the ties between biodemography and medicalclinical disciplines to better understand the link between functioning/diseases/vulnerability and mortality

While biodemography has been exceptionally successful in establishing strong ties to and collaboration with research areas as diverse as biology - especially evolutionary biology - genetics, epidemiology, and public health (Ewbank 2004; Carey and Vaupel 2005) links to the clinical sciences, in particular geriatrics, in the case of aging, and obstetrics, in the case of fertility, could be further developed. Specifically, biodemographic aging research traditionally uses mortality as outcome, but some studies also include the phenotypes that are most central to elderly people, namely physical and cognitive functioning. This is typically operationalized as ADL (activity of daily living) (Katz and Akpom 1976) and cognitive tests (such as MMSE - Mini-Mental-State-Examination) (Folstein, Folstein and McHugh 1975). These measures are known to be both valid and reliable and are by now well integrated in many biodemographic studies.

2.1 Including diseases in human biodemographic research

Diseases are occasionally included in biodemographic analyses, often in the form of cause-of-death or (number of) self-reported diseases. There is, however, considerable concern about the validity of disease assessment made this way, and collaboration with geriatrics is needed to improve this. Also conceptually, the terms "co-morbidity" and "multi-morbidity" (the latter used more in Europe) are often used interchangeably, but have different meanings. Multi-morbidity is the occurrence of several diseases in an individual, while co-morbidity denotes pre-existing diseases or conditions in reference to an index disease (e.g. diabetes (co-morbidity) will increase the mortality risk due to hip fracture (index disease)) (Yancik et al 2007).

The tradition of using number of diseases (often from a pre-existing list) as a measure of multi-morbidity has the advantage of being conceptually simple and easy to handle in statistical models, but it assumes that all the diseases on the list have the same impact and it ignores interaction and common etiologies. This is sometimes addressed by weighting and categorizations which on the other hand requires additional assumptions (Lash et al 2007). When diseases are included in the analyses it is furthermore important to be clear of the importance of the data source and its limitations (self-report, medical records, administrative data) and whether the co-morbidity/multi-morbidity is a confounder, a modifier (interactor), or an outcome in the analyses. Work is in progress to deal with these problems (Boyd et al 2007; Lash et al 2007), and the field of biodemography could clearly benefit from this development.

2.2 Including frailty/vulnerability in human biodemographic research

A concept in geriatrics receiving increasing attention is frailty - not the statistical model developed by Vaupel, Manton and Stallard (1979) - but a concept which is not equal to either ADL's or disease: a "clinical vulnerability" measure (Fried et al 2001). …

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