Within public health, we have many victories to claim. Vaccinations – for example – have been and remain unmitigated successes. Yet, there are many public health interventions that have been instituted and promoted by public health advocates, medical doctors, and various pharmaceutical or medical device companies that have proven to be ineffective at improving health outcomes. Nevertheless, without thorough and regular review, many of these interventions remain a part of public health messaging and part of clinical practice despite subsequent evidence showing their futility.
This post deals with four areas of preventative health services that have been part of public health programming for some time, but which the scientific evidence has either turned against or seems to be in the process of turning against, and which we should probably stop – or at least modify – in 2014.
There’s been a fair amount of press recently on vitamin supplementation. The industry is now worth more than $30 billion in US spending annually and yet newer systematic reviews of vitamin supplementation have produced a fairly clear picture that taking vitamin supplements has little to no effect on overall health outcomes and has produced some conflict as to whether vitamin supplementation is actively harmful or only marginally beneficial.
A few recent studies are worth noting. The most recent was published in December as an update for the US Preventative Services Task Force (USPSTF) in the Annals of Internal Medicine. The study concludes:
Limited evidence supports any benefit from vitamin and mineral supplementation for the prevention of cancer or [cardiovascular disease (CVD)]. Two trials found a small, borderline-significant benefit from multivitamin supplements on cancer in men only and no effect on CVD.
The second study published in the Journal of the American College of Nutrition in November reviewed a similar data set. The review analyzed MVM supplementation in relation to all-cause mortality, cancer specific incidence or mortality, or CVD mortality. The authors summarized their findings:
Based on a review of the evidence, MVM use does not appear to play a role in increasing risk of all-cause, cancer-specific, or CVD-specific mortality or cancer or CVD incidence. Collectively, MVM supplementation appears to have a slight inverse association with all-cause mortality. Evidence from 2 [randomized control trials (RCTs)] suggests that MVM supplementation may modestly lower cancer incidence and mortality, although observational epidemiologic studies do not confirm this inverse association […]. The opposite was true for CVD incidence and mortality: several of the large observational epidemiologic evidence supported a modest protective effect of MVM use […] and the 2 RCTs […] showed no effect.
The third study to highlight is the Cochrane Review Antioxidant supplements for prevention of mortality in healthy participants and patients with various diseases. The Cochrane Review analyzed 78 trials of beta-carotene, vitamin A, vitamin C, vitamin E, and selenium to conclude:
Overall, antioxidant supplementation either had no statistically significant effect or caused slightly increased mortality.
In the highest quality studies (those with lower risk of bias), antioxidant supplementation statistically significantly increased mortality.
Beta-carotene and vitamin E supplementation significantly increased mortality.
Vitamin A, vitamin C, and selenium had no statistically significant effect on mortality.
The authors concluded:
We found no evidence to support antioxidant supplements for primary or secondary prevention. Beta-carotene and vitamin E seem to increase mortality, and so may higher doses of vitamin A. Antioxidant supplements need to be considered as medicinal products and should undergo sufficient evaluation before marketing.
Based on these and other studies, several physicians and others have been advocating against continuing to recommend to the public that MVM supplementation is helpful in averting chronic disease. While there are certain groups for whom supplementation is clearly beneficial – such as pregnant women, vegans (who have a difficult time getting sufficient B12 from their diet), infants, and malnourished populations – among reasonably healthy people MVM supplementation is ineffective, wasteful, and potentially harmful – particularly if high doses are taken. Most of us get sufficient nutrients through our diet and should look to diet as the source of vitamins and minerals rather than supplementation.
PSA-Based Prostate Cancer Screening
According to the CDC, prostate cancer is the most common cancer in terms of incidence and the third highest cause of cancer related mortality in the United States. Though incidence rates and individual cancer rankings vary some, the CDC’s estimate is similar to those for the rest of the world, where female breast cancer has the highest incidence (it ranks 2nd in the US).
Despite the fact that prostate cancer is a major source of cancer related mortality, the evidence compiled since routine screening was introduced now shows that prostate cancer screening to prevent prostate cancer morbidity or mortality is ineffective and dangerous.
There are essentially two problems with prostate cancer screening in its current form. The first is that most men who live reasonably long lives develop prostate cancer at some point, but the prostate cancer is not life-threatening. Autopsy studies from the 1970s conducted around the world found that of men who died in their 50s from other causes, 30% had latent prostate cancer. For men who died in their 80s, latent prostate cancer findings were as high as 80%.
This leads to the second problem with prostate cancer screening – both PSA testing and DREs are notoriously inaccurate screening methods. PSA levels in the blood vary and can be influenced by many factors, including the presence of prostate cancer, but also as a result of recent sexual activity, benign prostate hyperplasia, and other conditions. In general, PSA levels in the blood below 4 nanograms per milliliter (ng/mL) are considered to not be suspicious while PSA levels above 4 ng/mL are considered suspicious for prostate cancer. PSA levels, however, are not particularly predictive of the presence or absence of prostate cancer, as upwards of 15% of men with PSA levels below 4 ng/mL still have prostate cancer, while approximately 76% of men with PSA levels above 4 ng/mL who undergo a biopsy have a false positive result (meaning they do not actually have prostate cancer).
In 2012, after reviewing the scientific literature, the USPSTF developed the recommendation that “Men who do not have symptoms associated with prostate cancer should not undergo screening.”
The table below is from the USPSTF’s report and is a model of what can be expected from continued PSA based screening for prostate cancer.
It should be noted that the vast majority of patients in the studies analyzed were white, with only approximately 4% of men involved in the studies being African-American – who have prostate cancer incidence rates that are more than double those of white men. However, a study which had nearly one-third African-American men did not find any difference in health outcomes in African-American men compared with white men.
This is not to suggest a shift in focus away from prostate cancer in the battle against cancer. Rather, the evidence calls for the public health community to put aside screening with ineffective diagnostics – which harms men overall – and to invest instead in developing far superior diagnostic technologies. From the CDC report, even “[i]f prostate cancer is diagnosed, there is no way currently to tell for sure if it is a cancer that will never cause a problem and does not need treatment or if it is an aggressive cancer that does need treatment”.
At the moment, most men in the US who are diagnosed with prostate cancer choose to undergo treatment, and face the side effects discussed in the above table, as well as the inherent dangers of surgery and radiation therapy. The vast majority of these men, however, did not need treatment as the cancer would not have developed to be life-threatening or even life-altering. Until we have technologies that can reliably determine the difference between latent prostate cancer and aggressive prostate cancer, screening itself is more harmful than beneficial and men and their doctors should seriously assess whether it is ethically justifiable to continue to subject men to such testing.
Asymptomatic Mammography-Based Breast Cancer Screening
Breast cancer screening faces many of the same problems as prostate cancer screening. The diagnostic test widely used – namely mammograms – is increasingly being shown to be ineffective and even harmful when including the effect of overdiagnosis, overtreatment, and the psychological harm of false positives or diagnosis of non-life threatening breast cancer.
In 2009, the USPSTF updated their recommendations on breast cancer screening:
The USPSTF recommends against routine screening mammography in women aged 40 to 49 years. The decision to start regular, biennial screening mammography before the age of 50 years should be an individual one and take into account patient context, including the patient’s values regarding specific benefits and harms. […]
The USPSTF recommends biennial screening mammography for women between the ages of 50 and 74 years. […]
The USPSTF concludes that the current evidence is insufficient to assess the additional benefits and harms of screening mammography in women 75 years or older. […]
The USPSTF concludes that the current evidence is insufficient to assess the additional benefits and harms of clinical breast examination beyond screening mammography in women 40 years and older […]
The USPSTF recommends against clinicians teaching women how to perform breast self-examination. […]
The USPSTF concludes that the current evidence is insufficient to assess additional benefits and harms of either digital mammography or magnetic resonance imaging instead of film mammography as screening modalities for breast cancer […]
Despite these recommendations having been made in 2009, they have not enjoyed widespread adoption. Many women continue to be advised to start screening at age 40 and are being screened annually.
In 2013, the Cochrane Review issued a new update on breast cancer screening effectiveness. Frankly, if you’re reading this blog post, I highly recommend you read the full Cochrane Review available here. After reviewing 8 studies comprising 600,000 women, the authors conclude:
Screening with mammography uses X-ray imaging to find breast cancer before a lump can be felt. The goal is to treat cancer earlier, when a cure is more likely. The review includes seven trials that involved 600,000 women in the age range 39 to 74 years who were randomly assigned to receive screening mammograms or not. The studies which provided the most reliable information showed that screening did not reduce breast cancer mortality. Studies that were potentially more biased (less carefully done) found that screening reduced breast cancer mortality. However, screening will result in some women getting a cancer diagnosis even though their cancer would not have led to death or sickness. Currently, it is not possible to tell which women these are, and they are therefore likely to have breasts or lumps removed and to receive radiotherapy unnecessarily. If we assume that screening reduces breast cancer mortality by 15% after 13 years of follow-up and that overdiagnosis and overtreatment is at 30%, it means that for every 2000 women invited for screening throughout 10 years, one will avoid dying of breast cancer and 10 healthy women, who would not have been diagnosed if there had not been screening, will be treated unnecessarily. Furthermore, more than 200 women will experience important psychological distress including anxiety and uncertainty for years because of false positive findings.
The author’s of the Cochrane Review end by stating:
We believe that the time has come to re-assess whether universal mammography screening should be recommended for any age group. Declining rates of breast cancer mortality are mainly due to improved treatments and breast cancer awareness, and therefore we are uncertain as to the benefits of screening today. Overdiagnosis has human costs and increases mastectomies and deaths. The chance that a woman will benefit from attending screening is small at best, and – if based on the randomised trials – ten times smaller than the risk that she may experience serious harm in terms of overdiagnosis. Women, clinicians and policy makers should consider the trade-offs carefully when they decide whether or not to attend or support screening programmes.
The harms from overdiagnosis are not insignificant. Overdiagnosis leads to overtreatment which include surgery and/or radiotherapy (overdiagnosis doesn’t appear to lead to increases in the use of chemotherapy). The damage and risks associated with surgeries are relatively clear, even with increasing breast-conserving surgical treatments. Studies have shown that radiotherapy causes a 27% increase in heart disease mortality and a 78% increase in lung cancer mortality.
Additionally, the psychological effects of overdiagnosis are not to be overlooked. Studies looking at women who experience a false-positive result during a mammogram report show that women remain troubled by the experience months and even years later.
Again, as with prostate cancer, it is critical that breast cancer remain a main focus of public health moving forward. However, it’s critical to recognize that the continued emphasis on self-breast exams, clinical breast exams, and mammography is likely misplaced in the era of significantly higher breast cancer awareness. Women should be much more fully informed of the risks associated with screening – specifically the risk of overdiagnosis and overtreatment of breast cancer. This point was reinforced in a recent article in JAMA which stated:
Going forward, the ability to design better screening programs will depend on the ability to better characterize the biology of the disease detected and to use disease dynamics (behavior over time) and molecular diagnostics that determine whether cancer will be aggressive or indolent to avoid overtreatment.
Certainly, genetic predispositions including family history of breast cancer or BRCA1 and BRCA2 genetic mutations are relevant indications for heightened scrutiny. However, it’s clearly time for women and their doctors to critically assess whether the continuation of mammography-based breast cancer screening in its current form can be ethically justified given that the benefits of generalized screening – specifically for women below the age of 50 – are dubious at best when weighed against the potential harms.
Obsessive Concern with Obesity based on BMI
“Overweight” and “obesity” based on BMI continue to take up a larger and larger percentage of the debate around public health. There’s good reason for this from an epidemiological perspective. Obesity around the world has been increasing at a rapid pace and carry with it a number of health concerns associated with weight gain.
However, as with all the points in this post, it’s not clear that the concentration on the traditional concepts of “overweight” and “obesity” are well placed. A systematic review of evidence published last year in JAMA looked at all-cause mortality correlated with standardized grades of BMI that were established by the WHO and National Heart, Lung, and Blood Institute. Normal BMIs (18.5 – 24) were compared against overweight (25 – <30), all-grade obesity (30+), grade 1 obesity (30 – <35), and grade 2 or 3 obesity (35+). The results suggest that we should re-think what is considered “normal” and question the continued clinical use of BMI as an independent indicator of health status.
The study found that overweight individuals had lower all-cause mortality, and grade 1 obesity had no statistically significant difference when compared to normal BMI individuals. All-grade obesity and grade 2 or 3 obesity had significantly higher rates of mortality when compared to the normal BMI controls. This means that from an all-cause mortality perspective, it is healthier to be somewhat overweight than to be in the traditional normal range for BMI – and this effect seems to become stronger as we get older.
What should be taken away from this? The first is that BMI tells us less about an individual’s overall health than the rhetoric around obesity would suggest. Certainly, there are many studies that have established significant correlative or causative relationships between weight/obesity and CVD, cancer incidence, type II diabetes, and a plethora of other conditions, and these are not to be discounted. This study does not indicate that that research is inaccurate, merely that there is a far more complex relationship between health and weight than can be encapsulated within BMI scores.
Instead, what we should be focusing on is the emerging evidence of the relationship between diet and disease, continuing to increase our knowledge of genetics and disease, and scaling back the judgmental manner in which obesity has been discussed for some time. There are very good reasons to be concerned about the levels of obesity in the world, but the relationships are not as clear cut as we have been led to believe. There’s a very good interview with Abigail Saguay – author of “What’s Wrong with Fat?” – about the risk of confirmation bias in obesity studies that fail to assess other factors independent of weight.
This post isn’t meant to change anyone’s individual behavior. Such decisions should be made in consultation with your doctor. What it’s meant to do is show that despite the very real concerns that exist relating to public health – particularly with diseases as terrifying and life destroying as cancer – doing something is always easier than doing nothing, but doing something isn’t always the correct approach either from an individual health perspective or from a public health perspective.
It’s far more critical that we be led by actual scientific evidence, rather than continue well-intended but ineffective programs simply because there’s not yet an alternative available.
The views reflected in this expert column are those of the individual authors and do not necessarily represent those of the O’Neill Institute for National and Global Health Law or Georgetown University. This blog is solely informational in nature, and not intended as a substitute for competent legal advice from a licensed and retained attorney in your state or country.