There is little evidence that people change their behavior when told they have a genetic risk for common diseases like type 2 diabetes or heart disease, according to a systematic review in The BMJ. Researchers focussed on diseases caused by complex interactions between multiple genes and environmental factors, finding that results of DNA tests had little or no effect on behaviors like smoking, diet or physical activity. The researchers say their results do not support expectations raised by proponents of personalized medicine and direct-to-consumer testing companies.
Dr. Robert Nussbaum, Professor Emeritus, University of California, San Francisco (webpage):
Expertise: If and how genetic and genomic information can be used to improve health care by improving outcomes, reducing adverse reactions, lowering costs and promoting health through risk education.
“The conclusion of this paper is exactly what I would expect when the kinds of genetic risks being communicated are very modest. Tests for common SNPs that alter odds ratios for disease by small amounts have low predictive value, and so I am not surprised that the results of such tests have little impact on behavior.
“Behavioral change is hard and throwing genetic information of low predictive value at the problem isn’t going to change that. Francis Collins says that a SNP test that showed he had a modest increased risk for diabetes motivated him to lose weight and exercise, but I think he is the exception. There has been a lot of hype about these tests, but even the new Chief Medical Officer of 23andMe has essentially jettisoned any claim that common SNP tests that are associated with modest increases in disease risk are anything other than a way to satisfy curiosity and explore the “Genomic Self”.
“That said, there are also genetic risk assessments for mutations with large impacts (pathogenic mutations in BRCA1, BRCA2, Lynch syndrome genes, long QT syndrome, etc.) that alter medical management a lot, although they still may not change peoples’ lifestyle choices. Even when someone tests positive for a Lynch syndrome mutation it can be hard to convince them to get a colonoscopy, despite a 5-10 fold increased risk for early onset colon cancer that is largely preventable by removing polyps.”
Beth Peshkin, Professor of Oncology, Senior Genetic Counselor, Georgetown Lombardi Comprehensive Cancer Center (webpage):
Expertise: Medical and behavioral outcomes of cancer genetic counseling and testing, bioethical issues in genetics.
“This review demonstrates the unsurprising finding that when individuals receive the results of some types of DNA tests, they do not significantly alter their diet, smoking habits, or levels of physical activity. But these results do not mean we should throw out the baby with the bathwater! Genetic testing is not the linchpin for motivating all types of behavior change or for treating and preventing every disease, but testing still plays a vital role in promoting health for some individuals in some circumstances, which is the essence of personalized medicine.
“Many of the studies included in the review assessed risk based on commonly occurring genetic variations. However, using this type of DNA testing to predict the risk of cancer and cardiovascular disease is highly imprecise and incomplete. For this reason, most of the genetic tests included in this review are not part of standard clinical testing and are not used to by health care professionals to guide a patient’s medical management. Preventing diseases resulting from smoking and obesity is a major public health challenge and this review affirms that research needs to focus on effective behavioral counseling and interventions that do not rely primarily on genomic feedback.
“Currently, the promise of genomic medicine lies predominantly in identifying mostly rare, high risk gene mutations that are associated with markedly increased risks for diseases or conditions such as hereditary breast, ovarian or colorectal cancer or predisposition to sudden cardiac death. For many individuals at increased risk for these conditions genetic testing has motivated them to pursue lifesaving medical tests or procedures.
“The bottom line is that not all genetic tests are created equal. Genetic counseling before and after testing can help individuals separate the hype from the evidence (or lack thereof). Such counseling also leverages a teachable moment to reinforce the contribution of other factors to disease risk and the benefits of a healthy lifestyle.”
Dr. Cecile Janssens, Professor, Deparment of Epidemiology, Emory University (webpage):
Expertise: Translation of genomics to applications in clinical and public health practice including assessment of the clinical validity and utility of predictive testing.
“This an important review because expectations are high that genetic testing can be used to motivate behavior change.
“Common diseases are polygenic: they are caused by complex interactions between multiple genetic and non-genetic factors, and the impact of each single variant is limited. When individuals are tested for a single genetic variant, which was done in 12 of the 18 studies reviewed, they might learn that their risk of disease increases from, say, 10% to 12%. Such small increases in risk are not expected to increase motivation, definitely not for behaviors that are difficult to change. It is therefore not surprising that randomized trials failed to show a significant impact.
“A weakness of the review is that it gives the suggestion that all genetic tests are equal. The authors pooled the results of small studies by performing separate meta-analyses for diet, smoking cessation and physical activity, because they consider that these behaviors are different. But they ignored differences between the genetic tests.
“For example, among the seven studies that investigated the role of genetic testing on diet: one study tested the APOE gene among people with a family history of Alzheimer’s disease; one study tested the FTO gene for obesity risk in students; and one study tested multiple type 2 diabetes genes in people who were overweight or obese. Altogether, the seven studies investigated seven different genetic tests in five different populations to predict the risk of six different diseases. Evidently, combining them in one meta-analysis makes no sense.
“The most important lesson from this review is that most randomized trials on the role of genetic testing in behavioral change were of poor quality. While future studies should be designed and conducted with more methodological rigor, expecting genetic tests to motivate lifestyle changes is quite optimistic. So unless unless the predictive ability of genetic tests can be improved perhaps more research on their behavioral impacts should be postponed.”
Dr. Brian Zikmund-Fisher, Associate Professor, Health Behavior and Health Education, University of Michigan (webpage):
Expertise: Decision psychology and behavioral economics to study factors that affect individual decision making about a variety of health and medical issues.
“Most (but not all) of the studies included in the review found little to no patient reaction to being informed that they carry gene variants related to disease. The main limitation of this finding is the type of meta-analysis carried out in the study does not take into account the degree that having the variant changes the patient’s risk of disease.
“Take APOE, the gene related to Alzheimer’s disease examined in one of the papers in the review. APOE has several variants. APOE3 is most common, and people who have two copies of APOE3 face average risk. Having one copy of APOE4 (rare) increases the risk of Alzheimer’s disease by 2-3 times, while having two copies of APOE4 (much rarer) increases it 15 fold. People receiving information that they have 2 copies of APOE4 should be far more motivated to act than people receiving information that they have only one copy. So the participants who are most likely to show an effect of receiving genetic information are rare, while most participants will have only weak reasons to change their behavior.
“In short, the absence of effect shown in this meta-analysis is not surprising: the people most likely to act on genetic information are few in number and hence we tend not to find effects on average. Yet, the current lack of evidence is not proof that communication of genetic findings cannot influence patients. Instead, it simply suggests that communicating genetic risk will likely be very useful to a small subset of patients rather than moderately useful to everyone.”
Declared interests (see GENeS register of interests policy):
Dr. Robert Nussbaum: “I am Chief Medical Officer of Invitae, a genetic information and testing company. We provide genetic testing for mutations in genes that have been well validated to harbor mutations that cause serious human diseases. Our tests can only be ordered by a genetics provider or physician and are not available direct-to-consumer.”
Dr. Brian Zikmund-Fisher: “I am co-investigator on a grant from the National Human Genome Research Institute examining the impact of whole genome sequencing for patients with rare cancers.”
‘The impact of communicating genetic risks of disease on risk reducing health behaviour: systematic review with meta-analysis’ by Hollands et al., published in The BMJ on Tuesday 15 March, 2016.