Introduction
Confounders are variables which are not measured in a study but may have an impact on the research. This paper analyzes the article by Chou et al. (2012), which identifies a risk factor for deep vein thrombosis, and considers a possible confounder in this study.
Apnea as a Potential Risk Factor for Deep Vein Thrombosis
The article by Chou et al. (2012) reports a study pertaining to identifying the sleep apnea as a potential risk factor for deep vein thrombosis. It is stated that the sleep apnea might be a potential confounder for deep vein thrombosis, but that the research had been lacking. Nevertheless, there is a variety of ways in which apnea may increase the likelihood of deep vein thrombosis; apnea is known to be associated with a number of conditions such as hypoxia, changes in the blood pressure, and hypercoagulation (Vijayan, 2012); the latter is a factor which most directly can increase the risk of deep vein thrombosis.
A Brief Description of the Study and the Confounders Identified
Chou et al. (2012) utilized a sample of 10185 patients in order to study the prevalence of emerging deep vein thrombosis over the course of 3.56 years (mean period). The patients with apnea developed deep vein thrombosis more often; the hazard ratio of 3.113 was reported at p=.002 (95% CI: 1.516-6.390). It is concluded that the apnea is a possible risk factor for deep vein thrombosis (Chou et al., 2012).
The authors also identified a number of confounders which might have influenced their study as well, such as the lack of information on smoking, body mass index, etc. (Chou et al., 2012); while it is noted that it was argued that smoking does not have an influence on deep vein thrombosis, obesity might still have a considerable impact (p. 379).
Another Possible Confounder and its Probable Effect on the Relationship between the Sleep Apnea and Deep Vein Thrombosis
There are factors which were not measured by Chou et al. (2012), but that may confound the relationship between the apnea and deep vein thrombosis. For instance, it is noted that one such factor is the diet of the patients (Mirrakhimov, 2012); an unhealthy diet might lead to higher levels of cholesterol, which may contribute to atherosclerotic plaques formation, making the chance of thrombi formation greater due to the fact that blood clots may form around the plaques.
Thus, an unhealthy diet of a patient might ultimately lead to atherosclerosis, increasing the likelihood of deep vein thrombosis as well. Clearly, it is unknown whether the participants in the apnea group more often had an unhealthy diet, but the differences (which might be related to lifestyles) might have existed. Therefore, it might be useful to look into more details pertaining to the way in which the relationship between apnea and deep vein thrombosis might be confounded by the diet of a patient.
In order to counteract the possible effect of unhealthy diet on deep vein thrombosis, it might be possible to assess the diet of the participants and include it as an additional variable.
Conclusion
Therefore, the article by Chou et al. (2012) investigates whether apnea might be associated with deep vein thrombosis (and, consequently, be a confounder in other studies). However, their study might also have been influenced by a number of confounders, such as the diet of the participants or their body mass index. To counteract the confounders, it is possible to include them as variables that are controlled for in a study.
References
Chou, K.-T., Huang, C.-C., Chen, Y.-M., Su, K.-C., Shiao, G.-M., Lee, Y.-C.,…Leu, H.-S. (2012). Sleep apnea and risk of deep vein thrombosis: A non-randomized, pair-matched cohort study. The American Journal of Medicine, 125(4), 374-380. Web.
Mirrakhimov, A. E. (2012). Sleep apnea and risk of deep venous thrombosis: Looking for potential confounders.The American Journal of Medicine, 25(11), e15. Web.
Vijayan, V. K. (2012). Morbidities associated with obstructive sleep apnea. Expert Review of Respiratory Medicine, 6(5), 557-566.