Sleep-disordered breathing a neglected risk factor in primary open-angle glaucoma

Background: Sleep-disordered breathing (SDB) is accompanied by large swings in blood pressure and the repetitive hypoxic period during sleep, which may accelerate anoxic optic nerve damage seen in glaucoma. There are many associated risk factors in primary open-angle glaucoma (POAG), but recently, SDB, though a neglected one, is coming up as a risk factor. However, various studies have reported controversial findings. Objective: To evaluate the relationship between SDB and POAG. Design : A hospital-based case-control study. Methods: A total of 400 patients between 30– 70 years were recruited from eye OPD between 2008- 2010. They were divided into two groups, 200 cases with established POAG and 200 age and sex-matched healthy subjects with normal IOP in the control group. Detailed history, complete ophthalmic and ENT examination was made along with BMI, blood pressure and neck girth measurement. Both groups were interviewed with a questionnaire regarding SDB and were recorded on the Epworth sleepiness scale (ESS). Results: The mean age being 55.02 ± 8.66 in the POAG group and male predominance noted both in POAG and SDB patients with ESS> 10 was statistically significant (p < 0.05). Also, patients in the POAG group with ESS > 10 had more IOP and BMI, greater neck girth, high BP and more ENT problems with p-value < 0,001, which is highly significant, thus showing the relationship between SDB and POAG. Conclusions: Increased community awareness and earlier detection of glaucoma and its correlation with SDB results in decreased morbidity.

pressure [16]. and leads to typical visual field defects and increased cupping of the optic disc. [17]. OAG is the most common type of glaucoma and is estimated to be responsible for 50% of glaucoma cases [18]. The prevalence of glaucoma in the general population is between 1% and 2%. [19]. According to WHO Tropical Journal of Ophthalmology and Otolaryngology 2021;6(4) (55%) in the POAG group with an ESS score of more than ten while 51 patients in the control group with ESS > 10. Statistically, this finding was highly significant (p < 0.001).           (47) in the POAG group and were statistically highly significant ( p < 0.001).  which was not significant. [29].
Age is considered a risk factor for both POAG and OSA. The incidence of OSAS in the general population has also been reported to be the highest between 45 -65 years of age. [30] The mean age in our study was 55 [39].
Other studies investigated a potential link between the presence of open-angle glaucoma and BMI or obesity [40,41]. In contrast, in a case-control study, no difference in BMI status was found in individuals with and without glaucoma [42].

Kaur M. et al: Sleep-disordered breathing a neglected
Tropical Journal of Ophthalmology and Otolaryngology 2021;6(4) IOP might get influenced by the haemodynamic system, autonomic nervous system and stage of sleep. [43]. SDB can affect these factors through changes in sleep architecture and an increase in blood pressure and sympathetic tone. The earlier studies conducted on glaucoma prevalence in OSAS reported a significant association between AHI and IOP. [10, 44,45] A study reported that an increase in IOP during lying can result in the development or progression of glaucoma in OSA patients [46]. But others found no correlation between IOP and RDI [28].
The change in pharyngeal size and shape due to obesity contributes to SDB. Fat storage in the neck may be particularly associated with risk for SDB, though a subset of patients with SDB are of normal body weight and have a family history of snoring or SDB. Factors affecting upper-airway size or patency include various anatomical variants and abnormalities like nasal obstruction, macroglossia, retrognathia, obesity, alcohol or sedative intake and body position during sleep. We found large neck circumference in 103 male patients, and 93 out of 110 patients in the POAG group with ESS > 10 had neck girth > 42 cms. Also, the male population in the study group had high blood pressure with more ENT problems (Table 4). Moreover, the incidence of these parameters was highly significant (P-value < 0.001) in the POAG group with SDB (ESS > 10,  47,48]. These co-morbidities are also risk factors for glaucoma and may contribute to our finding of a higher prevalence of glaucoma in the SDB group [49]. In the first half of the 1980s, a relationship was proposed between snoring, sleep apnoea and hypertension, initially supported by epidemiological studies that used self-reported snoring as a marker for sleep apnoea [50,51] and later, a correlation between sleep apnoea and increased cardiovascular risk was suggested [52]. Strong associations with systemic hypertension had been reported in glaucoma patients. [53,54] It is also reported that in the presence of other vascular risk factors, the optic nerve head blood flow may be reduced below a critical level due to physiological nocturnal hypotension and hence play a role in the pathogenesis of anterior ischemic optic neuropathy and glaucoma. [55].
On the other hand, SDB due to large swings in nocturnal blood pressure [56] and recurrent severe hypoxia [57]