The new star rating system is intended to help make personal health decisions and guide future research

The new star rating system is intended to help make personal health decisions and guide future research

A new series of meta-analyses highlights the often complex and contradictory health guidelines that link certain diets, behaviors and conditions to disease. The analyzes, conducted by researchers at the Institute for Health Metrics and Evaluation (IHME) at the University of Washington School of Medicine, were published today in Nature Medicine. IHME analyzed the strength of evidence for 180 pairs of risk factors and health outcomes - such as smoking and lung cancer, low-vegetable diets and type 2 diabetes, and high systolic blood pressure and ischemic heart disease. The results are presented in an easy-to-understand star rating system that shows the strength of the evidence for each link. The new star rating system is designed to help people make personal health decisions, inform health policy and guide future research.

There is extensive research into the relationships between various risks and health outcomes, but the results often vary widely across studies. One of the goals of this new star rating system is to eliminate confusion and help consumers make informed decisions about diet, exercise and other activities that can have a long-term impact on their health.

Dr. Christopher Murray, director of the Institute for Health Metrics and Evaluation and lead author of the study

In many areas, the IHME found that the association between a risk factor and a health outcome was weaker than some might believe. Almost two-thirds of the risk-outcome pairs examined – 112 of 180 – received only a one- or two-star rating. These include common combinations such as a diet high in unprocessed red meat and ischemic stroke (one star). In other cases, IHME's analysis confirmed the widespread consensus. Eight risk-outcome pairs received a five-star rating, including smoking and lung cancer, as well as high systolic blood pressure and ischemic heart disease. A list of star ratings including a data visualization tool can be found on the IHME website. More star ratings will be added in the near future.

The analysis takes into account both the extent of risk demonstrated in previous studies and the consistency of results between these studies. Star ratings are based on the most conservative interpretation of the available evidence to limit the impact of errors or biases in the underlying data. A one-star rating indicates that there may not be a true relationship between the behavior or condition and the health outcome. Two stars mean that the behavior or condition is associated with at least a 0–15% change in the probability of a health outcome, while three stars mean a change of at least 15–50%, four stars mean a change of at least 50–85%, and five stars mean a change of greater than 85%.

For example, the five-star rating for smoking and lung cancer means that smoking increases the chance of developing or dying from lung cancer by more than 85%. At the other end of the scale, the one-star rating for red meat and ischemic stroke means there may be no connection - in this case, because studies on the connection have produced inconsistent results.

Notable reviews from the study include:

“Our analysis not only helps consumers, but can also help policymakers develop health and wellness education programs to focus on the risk factors that have the greatest impact on health,” said Dr. Emmanuela Gakidou, professor of health metrics sciences at the Institute for Health Metrics and Evaluation and lead author of the study. “Health researchers can also use this analysis to identify areas where current evidence is weak and more definitive studies are needed.” The IHME researchers also note that while the meta-analytic approach used in this study should not replace expert advice, it can provide useful input to expert committees and advisory groups that make formal health policy recommendations.

The IHME analysis is based on the landmark Global Burden of Disease study, which celebrates its 30th anniversary this year, and is updated regularly. Due to constantly evolving research, star ratings may change as more data becomes available. This is especially true for pairings with low star ratings due to limited or conflicting research. On the other hand, high star ratings are unlikely to change significantly as the evidence is already compelling.

Source:

Institute for Health Metrics and Evaluation

Reference:

Zheng, P., et al. (2022) The Burden of Proof Studies: Assessing the Risk Evidence. Natural medicine. doi.org/10.1038/s41591-022-01973-2.

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