Older adults use the highest proportion of medical and pharmaceutical treatment, but are vastly underrepresented in clinical trial research. A recent review of publications based on randomized control trials (Zulman et al 2011) shows that this is not only a product of the under-recruitment of older adults. In addition to the use of age limits and other exclusion criteria that tend to preclude older individuals, most clinical research fails to look at outcomes of particular relevance to older adults. Further, many published studies employ statistical methods that may misrepresent the significance of age in their findings.
The authors performed a systematic review of all relevant articles published in five high-impact journals in the year 2007. The methods used in the articles were systematically coded, and the reviewers analyzed how age was used as an exclusion criterion, and for grouping study participants. The reviewers also analyzed the extent to which studies measured outcomes that are salient for older adults, such as physical function and quality of life. Most studies either excluded individuals over a certain age limit, or used eligibility criteria the exclude older adults. Researchers have an ethical obligation to minimize the risk of study participants, which motivates much of this exclusion. At the same time, researchers have another ethical obligation, which is to perform research that benefits at-risk populations. The authors acknowledge that many studies do not have the resources to include high-risk patients (such as individuals with multiple illnesses or cognitive limitations) in an ethical fashion. At the same time, it is troubling that so many studies preclude individuals based solely on age, regardless of health status.
The statistical shortcomings identified by the reviewers are not attributable to the ethical imperative to not harm subjects. The authors argue that many of the age-related conclusions drawn by clinical researchers are not statistically valid. For instance, many of the studies they reviewed draw conclusions that age did not make a difference in their findings, but did not report on whether or not the statistical power (basically, whether the study had enough participants that such non-differences are statistically meaningful) of the study was sufficient to draw this conclusion. On the other end of the spectrum, the authors argue that many of the studies that attributed different outcomes to age did not sufficiently explore possible confounding factors like pre-existing health status or multiple conditions.
The authors include some suggestions about improving the relevance of clinical trials for older adult populations. This includes not only being more inclusive of older adults, or individuals with medical conditions, but also by increasing standards of statistical analysis and examining outcomes of particular relevance to older adults. We should not underestimate the difficulties faced by clinical researchers in ethically recruiting and intervening with vulnerable participants. At the same time, we need to draw attention to the ageism behind how subjects are recruited and in how outcomes are measured.
Zulman DM, Sussman JB, Chen X, Cigolle CT, Blaum CS, Hayward RA (2011). Examining the Evidence: A Systematic Review of the Inclusion and Analysis of Older Adults in Randomized Controlled Trials. Journal of General Internal Medicine (e-pub ahead of print: DOI: 10.1007/s11606-010-1629-x)