|Year : 2018 | Volume
| Issue : 1 | Page : 8-11
Correlation between body mass index and intraocular pressure: A pilot study
Sophia Louisraj, Philip Aloysius Thomas, Christadass Arul Nelson Jesudasan
Department of Community Ophthalmology, Institute of Ophthalmology, Joseph Eye Hospital, Trichy, Tamil Nadu, India
|Date of Web Publication||4-Jun-2018|
Dr. Sophia Louisraj
Institute of Ophthalmology, Joseph Eye Hospital, Trichy, Tamil Nadu
Source of Support: None, Conflict of Interest: None
Purpose: The purpose of this study was to evaluate an association between body mass index (BMI) and intraocular pressure (IOP) in men and women. Materials and Methods: An observational study of 200 consecutive outpatients (90 males, 110 females aged 30–80 years), presenting at a tertiary eye hospital in southern India. Results: Ninety-four (47%) of the 200 participants had a normal BMI, 67 (33.5%) were overweight, and 33 (16.5%) were obese. Of the 33 obese participants, 19 (57.6%) were females. The mean BMI was 25.06 ± 4.66 and the mean IOP was 15.78 ± 3.99 mmHg. There was a positive, statistically significant, correlation between BMI and IOP (r = 0.2013, P = 0.004). Conclusion: Obesity is possibly a risk factor for increasing IOP in both men and women, with an increase in BMI being positively associated with increase in IOP. This is important in view of the current obesity epidemic.
Keywords: Body mass index, eye, intraocular pressure
|How to cite this article:|
Louisraj S, Thomas PA, Nelson Jesudasan CA. Correlation between body mass index and intraocular pressure: A pilot study. TNOA J Ophthalmic Sci Res 2018;56:8-11
|How to cite this URL:|
Louisraj S, Thomas PA, Nelson Jesudasan CA. Correlation between body mass index and intraocular pressure: A pilot study. TNOA J Ophthalmic Sci Res [serial online] 2018 [cited 2018 Jun 19];56:8-11. Available from: http://www.tnoajosr.com/text.asp?2018/56/1/8/233715
| Introduction|| |
Obesity in India has reached epidemic proportions in the 21st century, with morbid obesity affecting 5% of the country's population. Childhood obesity has become a serious public health issue and is steadily affecting many low- and middle-income countries, particularly in urban settings. Internationally, a body mass index (BMI) over 25 kg/m 2 is considered to be overweight, whereas a BMI of >30 kg/m 2 is considered obese. Since being overweight and obesity have become global epidemics, the question arises whether there is a relationship between obesity and elevated intraocular pressure (IOP). A number of studies have attempted to identify the risk factors associated with the development of elevated IOP. Several studies in western populations have suggested that age is related positively with IOP. Moreover, some epidemiological studies have examined a possible relationship between BMI and IOP; these studies suggest that high BMI is an independent risk factor for elevated IOP when considered with age and hypertension.
The current study aimed to evaluate a possible association between BMI and IOP in men and women.
| Materials And Methods|| |
This was an observational study on 200 consecutive outpatients presenting at a tertiary eye hospital in southern India, over a period of 3 weeks in November 2016. The institutional ethics committee approved the conduct of the study and all individuals who participated provided willful verbal consent.
Inclusion criteria included the following: Age between 30 and 80 years; either gender; IOP <30 mmHg. Individuals were excluded if even one of the following exclusion criteria was present: IOP >30 mmHg in either eye; a difference in IOP between the eyes exceeding 2 mmHg; the presence of glaucoma, corneal pathologies, or endocrine disorders.
Based on these criteria, 200 consecutive patients (90 males and 110 females, ranging in age from 30 to 70 years) were enrolled. All patients underwent a complete ophthalmological examination including visual assessment by Snellen chart, IOP measurement by noncontact tonometer, optical pachymetry to determine central corneal thickness (a corneal thickness of 540 μm was taken as normal and pressures were adjusted accordingly), and slit lamp examination of the anterior segment and the posterior segment using a +90 diopter lens. In addition, the weight (kg) and height (m) were also measured. BMI was calculated based on the formula:
BMI = Weight in kilograms/Height in square meters
Based on the calculated BMI (kg/m 2) values, the enrolled individuals were categorized as underweight if BMI was <18.5, as normal if BMI was 18.5–24.9, as overweight if BMI was 25–29, and as obese if BMI was >30 kg/m 2.
The data obtained were subjected to statistical analysis using Chi-square test and Pearson's correlation coefficient. P < 0.05 was considered to be statistically significant.
| Results|| |
A total of 200 individuals were screened. There were 90 males (45%) and 110 females (55%). The mean age of the participants was 50.32 ± 11.31 (range 30–70) years. The mean age (years) in females (50.77 ± 9.97) was higher when compared to males (49.88 ± 11.28).
The mean IOP (mmHg) was 15.78 ± 3.99 (95% confidence interval [CI] 15.22–16.33). The mean IOP (mmHg) in females (15.92 ± 4.05) was found to be higher than that in males (15.01 ± 3.84). The mean IOP (mmHg) in individuals with normal BMI (18–24.9 kg/m 2) was 15.2 (95% CI 14.43–15.96) but was found to be higher, that is, 15.48 (95% CI 14.26–16.69) and 17.3 (95% CI 15.67–18.92) for BMI categories 25–29 and >30 kg/m 2, respectively.
Body mass index
Applying the WHO guidelines to calculate the BMI, we found that 94 (47%) of the 200 participants had a normal BMI, 67 (33.5%) were overweight, and 33 (16.5%) were obese. Of the 33 obese participants, 19 (57.6%) were females. The mean BMI was 25.06 ± 4.66 (95% CI 24.41-25.705) kg/m 2. The mean BMI in males was 24.6 ± 4.64 kg/m 2, whereas in females, the mean BMI was 25.5 ± 5.02 kg/m 2.
Body mass index and age
In the current study, 54 (57.4%) of 94 individuals aged ≤50 years had a BMI <24.9 kg/m 2, whereas 46 (43.4%) of 106 individuals aged >50 years had a BMI <24.9 kg/m 2 [Table 1]. This difference was statistically significant (Chi-square = 8.8847, [degree of freedom (df) = 3]; P = 0.03). Furthermore, we found that there was a statistically significant, positive correlation between age and BMI (r = 0.1815, P = 0.01) [Figure 1].
|Table 1: Age distribution of study individuals in relation to subcategories of body mass index|
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|Figure 1: Scatter plot showing a putative correlation between body mass index (kg/m2) and age (years) in study individuals|
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Body mass index and gender
In the current study, 94 had a normal BMI; 58% of these were females and 42% were males. Of the 100 individuals who had a BMI >25, 47% were males and 53% were females. This difference was not statistically significant (Chi-square = 2.1844 [df = 3], P = 0.54) [Table 2].
|Table 2: Gender distribution of study individuals in relation to subcategories of body mass index|
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Body mass index and intraocular pressure
The mean IOP of all individuals was 15.78 ± 3.99 mmHg. Twenty individuals (10%) had an IOP >21 mmHg. Ninety-five % of those with a normal BMI, 91% of overweight, and 81% of obese had an IOP <21 mmHg.
Of 29 individuals who had a BMI ≤20 kg/m 2, 23 (79.3%) had an IOP <21 mmHg; of 171 individuals who had a BMI >20 kg/m 2, 157 (91.8%) had an IOP <21 mmHg; this difference was statistically significant (Chi-square = 4.306 [df = 1]; P = 0.037) [Table 3].
|Table 3: Intraocular pressure in study individuals in relation to body mass index|
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Correlation of body mass index and intraocular pressure
There was a positive, statistically significant, correlation between BMI and IOP (r = 0.2013, P = 0.004) [Figure 2]. When such a correlation (between BMI and IOP) was analyzed in males and females separately, we found that, there was a positive correlation between BMI and IOP, in both sexes (R = 0.0914 in males, R = 0.2798 in females); however, it was of statistical significance only in females (P = 0.004) and not so in males (P = 0.368).
|Figure 2: Scatter plot showing a putative correlation between body mass index (kg/m2) and intraocular pressure (mmHg) in the study individuals|
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Body mass index and comorbidities
Of the 200 participants, we found that 70 individuals (35%) had one or more comorbid conditions such as diabetes, hypertension, and ischemic heart disease, with 54% (n = 38/70) of these individuals having a BMI >25 Kg/m 2.
| Discussion|| |
This observational study, conducted over a period of 3 weeks, at a tertiary care hospital, evaluated the IOP in men and women with respect to their BMI levels. Overall, women were found to have a higher IOP than men, a finding consistent with that reported in some previous studies. Other studies, however, have found men to have a higher average IOP compared with women.
Interestingly, in our study, 53 (48.2%) of 110 females had a BMI of 25 kg/m 2 or greater, compared to 47 (52.2%) of 90 males. The mean BMI in our study was 25.06 kg/m 2. According to the current definition for obesity in the Asia-Pacific region, adults are considered to be overweight at BMI >23 and obese at BMI >25. We have used BMI values of >25 and >30, respectively, to define overweight and obesity in our population. BMI was found to be positively correlated to IOP in this study. A positive linear correlation between BMI and IOP was found in both men and women. When the IOP in individuals with normal weight (BMI <25 kg/m 2) was compared to the IOP in individuals with increased BMI, that is, subcategories 25–29 and >30 kg/m 2, the IOP was higher depending on the BMI subcategory. Similar results were seen in a study by Cohen et al., wherein the authors found a significant gradual increase in IOP for each increase in BMI subcategory. These changes remained significant after regressing for common reasons for increased IOP, that is, age and prevalence of hypertension and diabetes mellitus.
In the current study, it was also seen that the greater the age, the higher the BMI, especially in individuals above 50 years of age. Gordon et al. found that, with aging, the increased BMI was noted until 60 years of age after which it showed a tendency to decrease.
We can, therefore, infer that a greater age and higher BMI may be reflected in a higher IOP. These findings clearly show obesity to be a possible risk factor for increased IOP. The consistent elevation across the whole study group in both sexes, and the increased likelihood of abnormally elevated IOP in the higher BMI group, may add to other risk factors more prevalent in obese individuals for increased IOP.
Although there appeared to be a small increase in IOP in relation to BMI in the current study, individuals with abnormal BMI were found to have higher incidence of IOP >21 mmHg. It must also be remembered that glaucoma can occur in individuals with normal IOP, and it may not develop in some individuals with increased IOP. Hence, we cannot assume a correlation between BMI and glaucoma. Gasser et al. evaluated the direct effect of BMI on glaucoma and could not show such association. In a study by Flammer et al., it was emphasized that the element of vascular dysregulation rather than vascular atherosclerosis, in which BMI is a cofactor, was the major risk factor for glaucoma. Vascular dysregulation may lead to local vasospasms and disturbed autoregulation of blood flow in the optic nerve head, choroid, and other ocular tissues. This pathophysiologic pathway may explain why BMI will increase IOP but not necessarily increase glaucoma risk.
In the current study, 35% of the individuals were found to have other systemic comorbidities, such as diabetes mellitus, hypertension, and ischemic heart disease, out of which 54% were either overweight or obese. Hypertension and diabetes mellitus are very common in obese patients and are established risk factors for increased IOP. This may explain the incidence of increased IOP in obese individuals. There are possible suggested direct effects of obesity which can cause increase in IOP. It has been suggested that increased orbital pressure due to excess orbital fat may increase episcleral venous pressure and result in a decrease in outflow facility. Alternatively, the deposition of lipids has been suggested to reduce outflow facility for aqueous, thereby resulting in higher IOP in obese individuals.
| Conclusion|| |
- In both men and women, higher BMI is positively correlated with higher IOP. With a trend toward increasing IOP as BMI increased, we can surmise that BMI and IOP are definitely related, with obesity being a possible risk factor for high IOP
- Abnormal BMI associated with ageing, hypertension, and diabetes can compound this phenomenon. Regression analysis for age, diabetes, and hypertension will help to establish BMI as an independent risk factor for raised IOP
- However, normal IOP ranges according to BMI may need to be defined from population-based studies
- Obesity may be included as one among other risk factors, in a patient being assessed for glaucoma.
What is already known?
Abnormal BMI is associated with ageing, hypertension, and diabetes.
What does this study add?
IOP being the only modifiable risk factor in glaucoma, the BMI, due to its correlation to IOP, may be considered as yet another risk factor in the workup for glaucoma.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3]