Is There a Significant Relationship of Smoking and Obesity to Glaucoma
Written by Larry J Alexander OD FAAO Wednesday, 26 June 2013 Every once in a while you just have to step back and take a 30,000-foot view of things. When you read the following studies regarding proof of the risk of smoking on the worsening of glaucoma, you really need to put it in perspective. If you concede that vascular perfusion is a significant part of virtually every eye disease, you know that perfusion equates to the provision of oxygen to tissue. If you look at the lungs in the above photo, you pretty much have to figure that there is some cause and effect relationship between smoking and lack of oxygen to the eye. But let’s look at the studies.
AS A REMINDER OF OUR GOOD FORTUNE LISTEN TO THIS IF YOU HAVE TIME. IT WILL SHIVER YOUR TIMBERS:
If glaucoma is analyzed regarding reported associations and risk factors, the complexity of the issue of the disease is further amplified:
RISK FACTORS FOR GLAUCOMA
Hyper and Hypotension
History of Ocular Surgery
Low Intracranial Pressure
Oral, Topical, Inhaled Steroids
ASSOCIATIONS WITH GLAUCOMA
GLAUCOMA AND SMOKING
Every once in a while you just have to step back and take a 30,000-foot view of things. When you read the following studies regarding proof of the risk of smoking on the worsening of glaucoma, you really need to put it in perspective. If you concede that vascular perfusion is a significant part of virtually every eye disease, you know that perfusion equates to the provision of oxygen to tissue. If you look at the lungs in the above photo, you pretty much have to figure that there is some cause and effect relationship between smoking and lack of oxygen to the eye. But let’s look at the studies.
THE FACTS REGARDING SMOKING IN THE US
Perhaps the first question that must be addressed regarding smoking and glaucoma is whether or not smoking is an issue. If one reviews the latest information regarding smoking from the Centers for Disease Control, the answer is that smoking is a major health care issue in America and the World.
Percentage of U.S. adults who were current smokers in 2010:1
- 19.0% of all adults (43.8 million people)
- 31.5% non-Hispanic American Indian/Alaska Native
- 27.4% non-Hispanic multiple race
- 20.6% non-Hispanic white
- 19.4% non-Hispanic black
- 12.9% Hispanic
- 9.9% non-Hispanic Asian
Tobacco and marijuana use leads to disease and disability.
- Smoking causes cancer, heart disease, stroke, and lung diseases (including emphysema, bronchitis, and chronic airway obstruction).2
- For every person who dies from a smoking-related diease, 20 more people suffer with at least one serious illness from smoking.3
Tobacco use is the leading preventable cause of death.
- Worldwide, tobacco use causes more than 5 million deaths per year, and current trends show that tobacco use will cause more than 8 million deaths annually by 2030.4
- In the United States, smoking is responsible for about one in five deaths annually (i.e., about 443,000 deaths per year, and an estimated 49,000 of these smoking-related deaths are the result of secondhand smoke exposure).2
- On average, smokers die 13 to 14 years earlier than nonsmokers.5
Tobacco use costs the United States billions of dollars each year.
- Cigarette smoking costs more than $193 billion (i.e., $97 billion in lost productivity plus $96 billion in health care expenditures).1
- Secondhand smoke costs more than $10 billion (i.e., health care expenditures, morbidity, and mortality).6
Smoking is reported to increase the risk for virtually every human affliction because of the interference with the oxygenation of the blood and the increase in oxidative stress. 7-10 But….is there a proven relationship of morbidity in glaucoma related to smoking? Is there evidenced-based science to establish the link? Let us break down the studies in the pro and con discussion.
YES….THERE IS A PROVEN RELATIONSHIP OF SMOKING TO VISUAL IMPAIRMENT IN GLAUCOMA
It has been shown that inflammation and apoptosis marker levels increase in the aqueous and plasma of women smokers with POAG, the implication being that the apoptosis will further the functional loss. 11 The issue of smoking is proven to be a risk factor for the presence of glaucoma. 12-13 In one large collaborative study it was shown that surgically treated patients with glaucoma had lower IOPs if they were non-smokers. 14 From a functional standpoint, cigarette smoking is associated with a reduction in retinal sensitivity, the implication being that there will be further compromise of function with glaucoma. 15 In another interesting study on the effects of smoking on normotensive patients it was found that both IOP and BP increased secondary to the nicotine in cigarettes with the implication being that this somehow influences the functional loss of vision in glaucoma. 16
Another study reported that there was a relationship of smoking as a risk factor for glaucoma and was correlated with the central corneal thickness. 17 One recent study reported observations that suggested a protective effect of omega-3 fatty acids and a deleterious effect of heavy smoking and professional exposure to pesticides in POAG. 18
While the next section addresses the risk issue in obesity in more detail, one study found “that type 2 diabetes and current alcohol consumption are independent risk factors for POAG among African-American women, and that in addition to those factors, overall and central adiposity and smoking may be associated with increased risk of early-onset POAG.” 19
NO….THERE IS NO PROVEN RELATIONSHIP OF SMOKING TO VISUAL IMPAIRMENT IN GLAUCOMA
A 2008 study reported that smoking, alcohol use and female reproductive hormone use were not associated with glaucoma. 20 In a recent report among respondents with age-related eye diseases, the estimated prevalence of visual impairment was related to smoking in cataract patients and age-related macular degeneration but did not hold true for patients with glaucoma or diabetic retinopathy.21 It is also reported that the most critical risk factors associated with blindness in high-tension glaucoma, however, were elevated initial IOP, fluctuation, poor control, noncompliance and late detection, 22 while for primary angle-closure the risks include hypertension, family history, shallow anterior chamber and large CD with no relationship to smoking. 23
A recent 2011 study reported “there is conflicting evidence for living in a rural location, high blood pressure, diabetes and smoking” as it relates to the genesis of functional loss in glaucoma. 24 Even more astounding is the following from a 2012 report. “Increased age was a risk for Open Angle Glaucoma (OAG), and smoking decreased the risk of OAG compared to Ocular Hypertension (OH).” 25 Again, while the next section addresses obesity, a 2011 study reported that “obesity appears to be associated with a higher intraocular pressure and a lower risk of developing OAG. These associations were only present in women. Other lifestyle-related factors, such as socioeconomic status, smoking, and alcohol consumption, were not associated with OAG.” 26
First a blast from the past… http://www.youtube.com/watch?v=Zhk-XQjCnZY
The direct relationship to glaucoma appears to be controversial as studies and reviews fail to establish a firm link between either smoking or environmental smoke and glaucoma development. In spite of the lack of sound proof that smoking is a risk factor in reports, the same studies recommend that cessation of smoking is important in the management of glaucoma patients. 27-28 Edwards’ conclusion in the abstract of the in J Glaucoma 2008 report really summarized the issue and the conflict. “This systematic review provided little evidence for a causal association between smoking and development of POAG. Given the limited evidence from high quality studies, and the possibility that flaws in many of the studies reviewed biased the results toward the null, further high quality research to confirm our conclusions is needed. However, it remains important to warn ophthalmic patients of the dangers of smoking and provide cessation support owing to the clear evidence of links between smoking and other ocular and systemic diseases.” 29
To answer the question “does smoking have an effect on functional loss in glaucoma” from the standpoint of evidence-based medicine, one would have to be equivocal. There is no definitive proof that smoking has a deleterious effect on functional loss associated with glaucoma. But from 30,000 feet, I would challenge the definitions of glaucoma and methods of quantification that were utilized in all of these studies.
CAN THIS POSSIBLY BE ASSOCIATED WITH THIS
Advances in both structural and functional testing dictate that a well-controlled, well-defined trial is necessary to improve the understanding of the relationship of smoking, environmental smoke, and tobacco products as they relate to the progression of glaucoma. Take a look at the lungs of a smoker, the relationship of smoking to a number of systemic disorders, and then take a leap of logical faith to recommend to your patients that smoking increases risk of vision compromise in glaucoma. In spite of equivocal evidence-based studies.
GLAUCOMA AND OBESITY
INTRODUCTION TO OBESITY AND GLAUCOMA
Clinical Definition of Obesity:
For adults, overweight and obesity ranges are usually determined by using weight and height to calculate a number called the "body mass index" (BMI). BMI is used because, for most people, it correlates with their amount of body fat.
- An adult who has a BMI between 25 and 29.9 is considered overweight.
- An adult who has a BMI of 30 or higher is considered obese.
See the following for an example.
124 lbs or less
125 lbs to 168 lbs
18.5 to 24.9
169 lbs to 202 lbs
25.0 to 29.9
203 lbs or more
30 or higher
It is important to remember that although BMI correlates with the amount of body fat, BMI does not directly measure body fat. As a result, some people, such as athletes, may have a BMI that identifies them as overweight even though they do not have excess body fat.
A Body Mass Indicator Calculator for adults 20 years and older is available at http://www.cdc.gov/healthyweight/assessing/bmi/adult_bmi/english_bmi_calculator/bmi_calculator.html and relies on your height and your weight. Of course there are free downloadable applications for the BMI calculator.
Facts Regarding Obesity:
- More than one-third of U.S. adults (35.7%) are obese.
- Obesity-related conditions include heart disease, stroke, type 2 diabetes and certain types of cancer, some of the leading causes of preventable death.
- In 2008, medical costs associated with obesity were estimated at $147 billion; the medical costs for people who are obese were $1,429 higher than those of normal weight.
- Non-Hispanic blacks have the highest age-adjusted rates of obesity (49.5%) compared with Mexican Americans (40.4%), all Hispanics (39.1%) and non-Hispanic whites (34.3%) [See JAMA. 2012;307(5):491-497.]
- Obesity is Regional
Excessive weight and obesity in concert with an inappropriate diet loom as a constant threat to both systemic and ocular health especially when considering the impact of obesity on inflammation. 30-32 Morbidity and mortality are both affected by diet with a prudent approach being to maintain your weight at a reasonable level while coincidentally consuming health-sustaining nutrients.
Obesity and ocular disease appear to have a link for a number of different disorders.
There are studies linking obesity to macular degeneration. 33 There are reports of overall abdominal obesity increasing the risk for progression to advanced AMD, while more physical activity tended to decrease risk. 34-35 Ironically there is also an increased risk should the patient be too thin, assuming inadequate consumption of critical nutrients. 36 Can the clinician then assume that “too thin” equates to “too little nutrients” and then make the leap to an association of bariatric surgery to the long-term development of diseases such as ARM? Bariatric surgery results in the need for nutritional supplementation.
Another recent report suggested that the Latino population cardiovascular risk factors may play a role in advanced AMD. 37 This should be of no surprise since Richer’s original work demonstrated that cardiovascular risk factors including elevated serum iron (Fe) levels contributed to the progression of AMD. 38 Clearly obesity has a relationship to cardiovascular risk. The other risk factors often associated with heart disease such as smoking and altered blood composition are also modifiable in our patient base. 39
Reports also attest to the fact that obesity is actually related to a decrease in macular pigment levels that may be attributable to competition with adipose tissue. 40-41 Serum levels of lutein and zeaxanthin are the true measures of efficacy of supplementation and nutrition and both levels are measured lower with obesity and diabetes. All of these studies still do not absolutely indicate the need for diet control from a scientific standpoint, but all studies point to the necessity for cessation of smoking in minimizing the risk for AMD. 42
From the standpoint of cataract development there has been much discussion regarding diet. While very specific, studies have shown a link of metabolic syndrome with the genesis of cataracts. 43-45 In general it also appears that obesity is a positive marker for the increased likelihood of cataract formation while a bit unpredictable based on the type of cataract. 46 With a higher Body Mass Index (BMI), abdominal obesity, and diabetes patients develop a higher incidence of cortical and posterior sub-capsular cataracts. 47 The link of diabetes and obesity (most specifically the metabolic syndrome) is incontrovertible. 49-49
Metabolic syndrome denotes a common cluster of naturally connected risk factors including obesity, elevated blood pressure, insulin resistance, dyslipidemia, pro-inflammatory state and pro-thrombotic state. This scenario has the potential to lead to multiple retinal vascular flow issues within the eye. The link to diabetic retinopathy is more circumspect but studies have linked retinal microvasculopathy to metabolic syndrome. 50 Inhibition of inflammatory mediators is likewise implicated in minimizing diabetes risks 51 and can be achieved by dietary modification. A diet designed to address the metabolic syndrome seems to be the direction to go to minimize the risk of diabetic retinopathy. Additionally one must address other situations that may increase oxidative stress and decrease oxygenated blood supply to the eye such as smoking and sleep apnea.
Characteristics of the Metabolic Syndrome
- Abdominal obesity
- Atherogenic dyslipidemia
- Elevated Blood Pressur
- High insulin levels-over 10
- Raises fats into cells
- Promotes fat storage
- Stimulates arterial smooth muscle cells
- Promotes production of bad types of eicosanoid (EC) -intracellular hormones
- Series one ECs are good and may be inhibited by too much flaxseed
- Series two ECs are bad-glucagon is a strong inhibitor of EC 2 pathway
- Promotes retention of fluids by kidneys
Glucagon is the anti-insulin and is increased by high proteins low carbohydrates
- High levels of inflammatory mediators as measured by C-Reactive Protein levels
There is certainly a suggestion that there is an association of insulin resistance and the metabolic syndrome to increased intraocular pressure. 52-55 Body Mass Index also appears to have an association with elevated intraocular pressure. 56
In a recent report, three of five metabolic syndrome components (fasting plasma glucose, blood pressure, and triglycerides) were related to high-ocular tension. 57 A possible initial reaction to this fact of the relationship of increased IOP to obesity among clinicians would be to point to neck size and positive pressure as a related factor with sleep apnea falling into the picture. 58 The relationship of cerebrospinal fluid pressure elevation, Idiopathic Intracranial Hypertension, serum cortisol, and sleep apnea also create an interesting scenario for elevated intraocular pressure. 59 Inflammation associated with obesity also plays in to the equation.
While further analysis from a scientific standpoint is critical, it does appear, quite logically, that obesity has a link to increased intraocular pressure and possibly glaucoma if from no other standpoint than physical restriction of flow and associated inflammation. The metabolic syndrome issue plays quite a role in the equation as well. A quote from Arch Ophthalmol 2011 however, clouds the issue regarding obesity and glaucoma. The report concluded “Obesity appears to be associated with a higher intraocular pressure and a lower risk of developing OAG. These associations were only present in women. Other lifestyle-related factors, such as socioeconomic status, smoking, and alcohol consumption, were not associated with OAG.” 60
The clinician can read many things into this quote but should surmise that all disease is an accumulation of a number of contributing factors. My general rule is that a sick eye is usually associated with a sick body and to add a codicil, obesity certainly contributes to a sick body. In your conversation with the patient regarding glaucoma the suggestion that behavioral modification including weight reduction to achieve a better Body Mass Index will contribute to overall improved health, less likelihood of developing the Metabolic Syndrome and less likelihood of developing a “sick body” which could lead to a progression of the glaucoma.
- Is There A Significant Relationship Of Myopia And Axial Length To Glaucoma?
- Is There A Significant Relationship Of Central Corneal Thickness To Glaucoma?
- Marijuana And Glaucoma…
About the Author(s)
Dr. Alexander (1948-2016) was a 1971 graduate of Indiana University School of Optometry. He served in the US Navy then served as a Professor at the University of Alabama Birmingham School of Optometry. Larry contributed to a number of chapters in textbooks and has published three editions of Primary Care of the Posterior Segment, as well as contributed to the professional literature. He also lectured extensively in the area of ocular and systemic disease. His areas of special interest included dysfunctional tear syndrome, glaucoma and macular degeneration. His lessons are the basis for this site and he will be dearly missed.