Not something to sleep off Local study shows obstructive sleep apnea is a serious risk factor for cardiovascular disease
By Grace Roxas, Contributing Writer
A first-ever study on the prevalence of obstructive sleep apnea (OSA) among Filipino diabetics shows local basis for treating the condition as a risk factor for cardiovascular disease. Foreign data in the past have independently associated OSA and diabetes mellitus with hypertension, heart attack, stroke, atherosclerosis, and metabolic syndrome. In a cross-sectional survey at the University of the Philippines-Philippine General Hospital (UP-PGH) 14 percent of 317 patients with either type 1 or 2 diabetes were found to have symptoms of OSA. According to researcher Dr. Cherrie Mae Sison, this percentage is higher than the two to four percent prevalence of clinically important OSA in the general population and hews close to the findings of at least two similar small-scale foreign studies. The high OSA risk in the surveyed patients was significantly associated with a diagnosis of hypertension (p = 0.004) and other cardiovascular-disease (CVD) risk factors: obesity, increased waist, hip, and neck circumferences, elevated serum triglyceride level, and a diagnosis of metabolic syndrome. These associations are also cited as consistent with findings from a couple of past OSA studies on foreign subjects, one of them the Sleep Heart Health Study. "The estimated OSA prevalence rate of 14.1 in this study is significant in light of its association with cardiovascular risk factors. Hence, it is recommended that routine screening for OSA be considered in Filipino diabetic patients since it is a treatable risk factor," Sison said. For the screening, she proposes the use of the St. Luke's Medical Center Obstructive Sleep Apnea Clinical Score, the main evaluation instrument used for the UP-PGH study. Developed in 2000, the tool is said to be an inexpensive prediction rule that can easily be used at bedside or in a clinic. Patients evaluated as high risk for OSA should then be sent for formal sleep studies. Although no causal links were established between OSA and the other risk factors, the association points to a progression from untreated OSA and subsequent onset of hypertension and metabolic syndrome. The restricted airflow to the lungs due to obstruction, the condition characteristic of OSA, is thought to trigger chemical and physical changes leading to wide and sudden blood-pressure fluctuations that over time can lead to sustained hypertension and heart damage. Endocrinologist Nemencio Nicodemus Jr. of the UP College of Medicine notes that as apnea decreases the level of the vasodilator nitric oxide and increases levels of enzymes that convert to angiotensin II, a potent vasoconstrictor, there will be greater constriction leading to hypertension. High levels of certain inflammatory markers (i.e. tumor-necrosis-factor alpha, IL-6) contributing to endothelial dysfunction and hypertension are also found in people with sleep apnea, particularly those who are obese. He cites a 2000 study that noted the positive correlation between the incidence of nightly apnea episodes over one year among patients followed for four years and the likelihood of developing hypertension on the fourth year. A higher than normal association with high blood pressure was also observed among those who snore, wake frequently during the night, or have mild sleep apnea. The link to metabolic syndrome is thought to be mediated by increased waist circumference or visceral obesity and elevated triglyceride levels although the more telling connection to insulin resistance cannot be established by the study. Sison notes that as a structural problem possibly involving blockage in the upper airways, OSA may be linked to diabetes through obesity. Nicodemus observes that the association between sleep apnea and obesity remains a chicken-and-egg problem. "This is a controversy at the moment. Some studies indicate that sleep apnea disrupts rapid-eye-movement (REM) sleep, which in turn increases risk for obesity because animals deprived of REM sleep tend to eat more. On the other hand, people with apnea may also become too tired to exercise and so put on more weight." The study also looked into the incidence of OSA-induced excessive daytime sleepiness in diabetics and their quality of life, but the findings were less conclusive. Aside from daytime sleepiness, neurophysical changes characteristic of OSA are daytime fatigue, morning headaches, memory impairment, and personality disturbances. M
Grace Roxas, Contributing Writer
More Filipino babies than previously thought may be at risk for serious hearing impairment, leading to a significant lag in their language and social development. A 2005 study correlating hearing screening with the two-year development of Filipino infants showed a higher-than-expected prevalence rate (one per 724 babies) of bilateral profound hearing loss, more than the usual one per 1,000 reported in Western studies. This translates to lower-than-average development scores in general and across all subscales having to do with locomotor, personal and social functions, hearing and speech, eye-hand coordination, and performance of the profoundly impaired babies, according to the study conducted by the Philippine National Ear Institute of the University of the Philippines-National Institutes of Health (UP-NIH). Even those with mild hearing loss, whether unilateral or bilateral, have at least a 40 percent lower than average mental development, suggesting that while cases of bilateral severe hearing losses demand priority care, those with milder conditions should also be targeted for intervention. Dr. Charlotte Chiong, one of the study authors, says these findings should prompt the scaling up of newborn hearing screening from being a service offered only to high-risk neonates and children in tertiary hospitals to a universal procedure mandated on a community-level health setting. "As part of the medium-term goals of universal primary education worldwide, I think we should include universal hearing screening there. It is very important for good education," she notes. She adds that a community-based hearing screening may provide distinct advantages over hospital-based programs employed in other countries, with only 36 percent of Philippine births happening within hospital facilities and given the local experience of very poor follow-up rates, even among those who failed an initial hearing screening. Otoacoustic emission (OAE) and auditory brainstem response (ABR) tests were used to good effect under the study, conducted among a cohort of pregnant women in several rural communities in Bulacan province starting 2002. The simpler OAE test, in particular, is the recommended tool for universal hearing screening in the local setting. Institutionalizing universal hearing screening has a long way to go, although it is by no means undoable. Chiong notes that at present, even babies recommended for this procedure are not being tested within the ideal screening window of between three and six months after birth. There are still a number of babies screened after six months despite their method of actively identifying cases by going house to house. The cost of identifying one case of bilateral permanent hearing loss is also pegged at a staggering US$5,000 to US$56,045 in developed countries although the cost might be cheaper in the Philippines, based on unpublished estimates. Dr. Soledad Antonio, chief legislative liaison for the Department of Health (DOH), emphasized the need for a cost-benefit analysis in instituting a universal-hearing-screening program and the pivotal role of local-government units in primary-health decision making. "Screening the population is a must in public health. It is common and valuable. It is also true that we can ride this in our maternal and child program. But the issue is, will it be more beneficial compared to other programs with externalities, given a developing country like us with limited resources?" she asks. Dr. Sylvia Estrada, head of the NIH's metabolic-newborn-screening program, indicates that the now mandatory metabolic screening procedure may be a good model as well as vehicle for a universal hearing screening initiative to take off. She notes that the drafting of the metabolic-newborn-screening law in 2004 gave a big push to the initiative. "The first step was really to get the DOH imprimatur," Estrada said of their experience in advocating metabolic newborn screening. "We have to speak to mayors and convince them. They're very creative. Money was not an object. In fact, it was those who can't afford who were more enthusiastic to think of ways to make newborn screening available." She adds: "Maybe with the network that has been set up for (metabolic) newborn screening, madali nang isakay ang hearing screening. Cost would be even lesser." M |
