They can influence what clothes people wear, what music people listen to and what food people eat. The power of celebrities is well known in the realm of popular culture, but what influence do they have when it comes to public health?
While many celebrities can stake a claim to knowing a thing or two about how to "look good" and what the latest fashions are, the same cannot usually be said about health and medicine. And yet, despite this, the opinions and experiences of celebrities frequently influence how people approach their own health.
Even in the face of the expert opinions of doctors, physicians and academic researchers whose professional lives are focused on improving and delivering the best health care possible, people can sometimes be influenced more by the actions of a film star.
"People are trusting celebrities with their health," write researchers from McMaster University in Ontario, Canada. Steven J. Hoffman and Charlie Tan conducted a meta-narrative analysis of literature concerning celebrities' medical advice in 2013, examining its effects from economic, marketing, psychological and sociological standpoints.
This trust, however, is sometimes misplaced. "While celebrities sometimes encourage healthy behaviors of proven benefit, at other times they spread misinformation and harmful practices," they state.
In this Spotlight, we take a look at some recent examples of how celebrities have influenced health care, for better and for worse. We will then briefly examine the possible mechanisms that could be behind this powerful influence.
Getting tested: the 'Angelina and Jade effects'
A study revealed that in the wake of this announcement, genetic testing referrals among high-risk women rose by two-and-a-half times in the following 2 months. A two-fold increase in testing referrals remained for 5 months following her article discussing the decision.
The researchers conducting the study - published in Breast Cancer Research - reported that there were also many more enquiries for risk-reducing mastectomy, and that an internal review showed that there had been no simultaneous increase in inappropriate referrals.
"The Angelina Jolie effect has been long lasting and global, and appears to have increased referrals to centers appropriately," they concluded.
Study co-author Gareth Evans, of Genesis Breast Cancer Prevention and St. Mary's Hospital in the UK, described the potential impact of Jolie's announcement, stating that it was likely to have had a bigger impact than other celebrity announcements, possibly due to her image as a glamorous and strong woman.
"This may have lessened patients' fears about a loss of sexual identity post-preventative surgery and encouraged those who had not previously engaged with health services to consider genetic testing," he said.
It was not the first time that Angelina had influenced cultural trends. An article in TIME suggested that when she adopted a baby from Ethiopia, inquiries at adoption centers in the US for Ethiopian orphans doubled.
However, it is not just Academy Award-winning actors that can have a significant impact on health care trends. In the UK, when British media personality Jade Goody publicly announced her cervical cancer diagnosis, it led to a surge in cervical screening attendances.
A study published in the Journal of Medical Screening reported that about half a million extra cervical screening attendances occurred in England during the period in which Jade Goody announced her diagnosis and died, with attendances 70% higher than expected at their peak.
"The pattern of increased attendance mirrored the pattern of media coverage of Jade Goody's diagnosis and death," the authors write. "It is likely that the increased screening resulted in a number of lives saved."
These examples are just two of the many incidences where the personal experiences of a public figure have led to significant change in the behaviors of the public toward their health leading to substantial benefit. However, the same can not be said for all examples of celebrity influence.
Going against the grain and the anti-vaccination movement
Many people will be accustomed to TV appearances and column inches being dedicated to the latest dietary fads and health tips that are being touted by celebrities as the newest greatest thing. Sometimes these are based on personal experience, but at other times commercial interest can influence a decision to promote something.
While it is one thing to promote a certain item of food as healthy, however, it is quite another to recommend a form of medical practice, especially if it concerns a particularly deadly disease such as cancer and the practice in question does not conform to mainstream medical opinion.
In their analysis, Hoffman and Tan identify a number of examples where celebrities have promoted or recommended medical practices that conflict with the established ways of thinking in the medical field.
British TV presenter Sir Michael Parkinson advocated a method of self-diagnosis for prostate cancer that entailed checking whether it was possible to urinate against a wall from two feet away. Actor Suzanne Somers recommended her own brand of medicine to reverse aging and for pancreatic cancer, despite a lack of evidence for the therapies' efficacy.
Some might consider these positions to be examples of free-thinking, stating that it is important to challenge established ideas. When it comes to established medical opinion, however, it is arguable whether actors and TV presenters are the people best positioned to do the challenging.
Actor Jim Carrey wrote an article about the dangers of vaccines for The Huffington Post in 2009 in which he said the following:
"In this growing crisis, we cannot afford to blindly trumpet the agenda of the CDC, the American Academy of Pediatrics (AAP) or vaccine makers. Now more than ever, we must resist the urge to close this book before it's been written."
"Anti-vaxxers have been relentless in the efforts to spread misinformation. Despite overwhelming scientific evidence that vaccines are beneficial, they endlessly repeat a variety false claims," wrote Steven Salzberg, a professor of biomedical engineering, computer science and biostatistics at Johns Hopkins University School of Medicine in Baltimore, MD, in Forbes earlier this year.
One of the biggest fears concerning vaccinations has been that they could lead to autism spectrum disorder in children.
"Over the past 15 years, dozens of studies involving hundreds of thousands of people have shown convincingly that neither vaccines nor any of the ingredients in them are linked to autism," said Prof. Salzberg. "Vaccines are not only safe, but they are perhaps the greatest public health success in the history of civilization."
One website calculates the number of vaccine-preventable illnesses(resource no longer available at www.antivaccinebodycount.com) that occur in the US using data obtained from the Centers for Disease Control and Prevention's (CDC) Morbidity and Mortality Weekly Reports for case numbers of diseases such as measles, mumps, rubella, whooping cough and chickenpox.
The website then reports the number of vaccine-preventable illnesses and deaths that have occurred since June 3rd, 2007 - a year in which the website says "there was an increase in celebrities promoting anti-vaccination rhetoric."
To date, this website suggests 149,958 vaccine-preventable illnesses and 9,020 preventable deaths occurred between June 3rd, 2007, and May 9th, 2015. During this period, the site also suggests there have been no autism diagnoses scientifically linked to vaccinations.
'Trust me, I'm a celebrity'
So why is that people with little or no medical experience can have such a significant influence on public health trends? In their analysis, Hoffman and Tan state there are multiple mechanisms that explain the influence of celebrities that can be grouped into four different categories:
Celebrity endorsements act as signals of superiority, distinguishing endorsed forms of treatment and opinions from the alternatives. People also have a tendency to make decisions based on what others have done in similar situations - in this instance, people often want to follow in their favorite celebrities' footsteps.
People often see attributes in celebrities they respect and wish to emulate. This respect can lead people to follow the advice and actions of celebrities in the hope of acquiring these traits. There is also the "halo effect," whereby the success of celebrities gives them a cloak of "generalized trustworthiness that extends well beyond their industry or expertise."
Beliefs and practices that are endorsed by celebrities come to elicit the positive responses many people associate with their favorite celebrities. Images projected by celebrities are often used to define individuals' self-conception so that their advice may be compatible with an individual's ideal self and push them to follow that advice.
Also, people typically desire to maintain mental consistency. Ignoring a favorite celebrity's medical advice may conflict with their adoration for that celebrity.
Newsworthiness and the star quality of celebrities allow them to feature prominently within social networks and achieve great influence. "People 'purchase' celebrity by acquiring celebrities' products, mimicking their lifestyles, and heeding their medical advice," the authors write. Doing so gives individuals social capital, raising their social status.
The long-term effects of celebrity
A few months ago, Carrey sent out a series of messages on Twitter in response to the California government passing a law that removed the ability for parents to opt out of vaccinating their appropriately-aged children for personal or religious reasons, implying that mandatory vaccines contain dangerous levels of mercury and aluminum. These tweets illustrate the longevity of the anti-vaccine message.
Other examples of the celebrity influence in health care are not as long-lasting. In one example, the "Jade Goody effect" observed in the UK wore off within years of cervical screening attendances reaching significant highs.
A cervical cancer charity in the UK reported that testing for cervical cancer among women in England had fallen to a 10-year low in 2012, with around 20% of women not attending recommended screening.
In the case of Angelina Jolie influencing the number of genetic testing referrals, these also began to fall 5 months after her public announcement.
For celebrities to continue to have an influence on public health, it would appear that their messages need to remain in the spotlight.
In the conclusion to their analysis, Hoffman and Tan suggest that health professionals could utilize the influence of celebrity status in order to improve public health practice.
"A better understanding of celebrity can empower health professionals to take this phenomenon seriously and use patient encounters to educate the public about sources of health information and their trustworthiness. Public health authorities can use these insights to implement regulations and restrictions on celebrity endorsements and design counter-marketing initiatives - perhaps even partnering with celebrities - to discredit bogus medical advice while promoting evidence-based practices.
Rather than allowing the messages of celebrities to speak louder than their own, health professionals could utilize the influence of celebrity to amplify their knowledge and ensure that expert opinion is heard by as many people as possible.