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Communications to the Editor |

Sleep Apnea Devices and Sleep Apnea Surgery Should Be Compared on Effectiveness, Not Efficacy FREE TO VIEW

Edward M. Weaver, MD, MPH
Author and Funding Information

Affiliations: University of Washington School of Medicine Seattle, WA,  Central Hospital %Västerås, Sweden

Correspondence to: Edward M. Weaver, MD, MPH, University of Washington School of Medicine, Box 358280, MS 112-OTO, Seattle, WA 98195; e-mail: eweaver@u.washington.edu



Chest. 2003;123(3):961-962. doi:10.1378/chest.123.3.961
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To the Editor

Walker-Engström et al stated in their article in CHEST (March 2002)1 that treatment with a dental appliance “showed a significantly higher success and normalization rate” and thus had “superior effectiveness” than uvulopalatopharyngoplasty (UPPP) for the treatment of obstructive sleep apnea. Although this study had many strengths, such as randomization, long follow-up, and blinded sleep study interpretation, the conclusion depended on a key methodological fallacy that is common in studies such as this. I offer a quantitative analysis to show that their conclusion is not just “partly invalidated” by suboptimal compliance but, rather, is completely invalidated.

It is critical to distinguish efficacy (ie, the effect in the laboratory under ideal conditions) from effectiveness (ie, the effect in everyday life)2when comparing surgical and nonsurgical treatments for sleep apnea. Effectiveness is far more relevant than efficacy to clinical practice. A perfect laboratory value with the device on (ie, efficacy measure) is of no help to the patient who does not wear the device outside the laboratory. Treatment adherence is not an issue with surgical therapy. Thus, it makes sense to compare only the effectiveness of surgical and nonsurgical treatments. It is a fallacy to compare the efficacy. Rather than exclude subjects who failed to receive or use their randomly assigned treatment, the authors should have counted those subjects as treatment failures in an assessment of effectiveness, as is required in a true intention-to-treat analysis.3

Including these treatment failures reduces the 4-year apnea index success rate of the dental appliance from 81% (32 patients) to 54% (48 patients), and that of the UPPP from 53% (40 patients) to 49% (43 patients). The difference between treatment groups is no longer statistically significant (p = 0.68 [Fisher exact test]). Likewise, both the 4-year apnea-hypopnea index success rate and the normalization rate are no longer statistically different (p = 0.20 and p = 0.28, respectively). The results are similar even if we exclude the subjects who dropped out due to unrelated medical problems (p = 0.67, p = 0.13, and p = 0.27, respectively). Furthermore, the sleep study values obtained while patients wore the dental appliance in the laboratory should be corrected for the actual usage in everyday life in order to measure treatment effectiveness.4

The fact that patient satisfaction (which is an inherent measure of effectiveness rather than a measure of efficacy) with UPPP was as high as with the dental appliance (satisfied subjects: UPPP, 30 of 46 subjects; dental appliance, 27 of 46 subjects)1 suggests that these treatments have similar effectiveness. In fact, the authors have reported previously5 that quality-of-life contentment (another inherent measure of effectiveness) improved significantly more for patients in the UPPP group than for those in the appliance group.

The suboptimal effectiveness of each individual treatment for sleep apnea (including continuous positive airway pressure4) suggests the need for complementary and collaborative treatment regimens.

References

Walker-Engström, M-L, Tegelberg, A, Wilhelmsson, B, et al (2002) 4-year follow-up of treatment with dental appliance or uvulopalatopharyngoplasty in patients with obstructive sleep apnea: a randomized study.Chest121,739-746. [PubMed] [CrossRef]
 
Last, JM A dictionary of epidemiology.1995,52 Oxford University Press. New York, NY:
 
Friedman, LM, Furberg, CD, DeMets, DL Fundamentals of clinical trials.1998,284-293 Springer. New York, NY:
 
Grote, L, Hedner, J, Grunstein, R, et al Therapy with NCPAP: incomplete elimination of sleep related breathing disorder.Eur Respir J2000;16,921-927. [PubMed]
 
Walker-Engstrom, ML, Wilhelmsson, B, Tegelberg, A, et al Quality of life assessment of treatment with dental appliance or UPPP in patients with mild to moderate obstructive sleep apnoea: a prospective randomized 1-year follow-up study.J Sleep Res2000;9,303-308S. [PubMed]
 

To the Editor:

We thank Dr. Weaver for his comments on our article that was published in CHEST (March 2002).1

No treatment is effective if patients are not compliant. This is an inherent problem when comparing the effects of nonsurgical treatments to those of surgical treatments. Patients can stop taking drugs or, in this case, can stop using a dental appliance. Once operated on, however, they cannot withdraw from treatment. Even in the best-designed, best-managed, short-term clinical trials, there will be patients who withdraw.2 In a clinical trial in which treatment extends over an unusually long period (4 years in our study), the risk of withdrawals from treatment, as expected, increases quite a lot, even though the results of a clinical trial often differ from the those of clinical practice because of the careful monitoring of patients in the trial. Therefore, it might be more appropriate to use the term efficacy instead of effectiveness in clinical trials. The careful description of the number of withdrawals and the exact reasons for them are important issues in interpreting the results in a clinical trial. Such an analysis was performed in our study. That compliance is an important response variable is well-documented in our article and is also included in the conclusion section of the article.

Two of the response variables presented in our article are success rate and normalization rate. In his reappraisal of our article, Dr. Weaver assumed that all the patients who withdrew from treatment had nonnormal somnographic values after 4 years, and thus, he in turn placed them in the unsuccessful and nonnormalized group. Thus, Dr. Weaver introduced an extreme assumption into his calculations. For several reasons, which are carefully described in the article, none of the patients who withdrew from treatment was examined after 4 years with somnography. These patients could have attained normalization using the somnography measurement if they had attended the 4-year follow-up. The results of an examination for an individual patient cannot be predicted; they must be measured.

We think our study has a sound basis for the conclusion that the use of a dental appliance with regular follow-ups can be recommended for long-term treatment.

References
Walker-Engström, M-L, Tegelberg, A, Wilhelmsson, B, et al 4-year follow-up of treatment with dental appliance or uvulopalatopharyngoplasty in patients with obstructive sleep apnea: a randomized study.Chest2002;121,739-746. [PubMed] [CrossRef]
 
Friedman, LM, Furberg, CD, DeMets, DL Fundamentals of clinical trials.1998,284-297 Springer. New York, NY:
 

Figures

Tables

References

Walker-Engström, M-L, Tegelberg, A, Wilhelmsson, B, et al (2002) 4-year follow-up of treatment with dental appliance or uvulopalatopharyngoplasty in patients with obstructive sleep apnea: a randomized study.Chest121,739-746. [PubMed] [CrossRef]
 
Last, JM A dictionary of epidemiology.1995,52 Oxford University Press. New York, NY:
 
Friedman, LM, Furberg, CD, DeMets, DL Fundamentals of clinical trials.1998,284-293 Springer. New York, NY:
 
Grote, L, Hedner, J, Grunstein, R, et al Therapy with NCPAP: incomplete elimination of sleep related breathing disorder.Eur Respir J2000;16,921-927. [PubMed]
 
Walker-Engstrom, ML, Wilhelmsson, B, Tegelberg, A, et al Quality of life assessment of treatment with dental appliance or UPPP in patients with mild to moderate obstructive sleep apnoea: a prospective randomized 1-year follow-up study.J Sleep Res2000;9,303-308S. [PubMed]
 
Walker-Engström, M-L, Tegelberg, A, Wilhelmsson, B, et al 4-year follow-up of treatment with dental appliance or uvulopalatopharyngoplasty in patients with obstructive sleep apnea: a randomized study.Chest2002;121,739-746. [PubMed] [CrossRef]
 
Friedman, LM, Furberg, CD, DeMets, DL Fundamentals of clinical trials.1998,284-297 Springer. New York, NY:
 
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