Abstract 2529: A prospective cohort study of body size and risk of head and neck cancers in the NIH-AARP Diet and Health Study.
Authors: Etemadi Arash , O'Doherty Mark G. , Freedman Neal D. , Hollenbeck Albert R. , Dawsey Sanford M. , Abnet Christian C. 
Published: August 2014

Abstract
Background: The association between body size and head and neck cancers has not been well understood, partly because of the biases in case-control studies (such as reverse causation due to pre-diagnosis weight loss and use of recalled weight), and partly because of the difficulties in adjusting for confounders such as tobacco smoking. The only published cohort study on this relationship showed reduced mortality, but not incidence, among overweight and obese people, which was only significant among smokers.
Methods: In the prospective NIH-AARP cohort study, 218,854 participants (132,288 men and 86,566 women) aged 50-71, were cancer-free at baseline, and had valid data on weight, height, and waist and hip circumference. Cox proportional hazards regression was used to examine the associations between overall (BMI) and abdominal (waist and waist-to-hip ratio) body size and head and neck cancers (squamous cell carcinomas of the oral cavity, oro-and hypopharynx, larynx, and nasopharynx). The analyses were adjusted for confounders, among them current and past smoking habits, alcohol intake, education, race and fruit and vegetable consumption. Additional analyses were also done separately among never- and ever-smokers.
Results: During follow-up from the study baseline (1995 and 1996) to 31 December 2006, a total of 779 incident head and neck cancers accrued to the cohort, including 342 in the oral cavity, 120 in the oro- and hypo-pharynx, 265 in the larynx, 12 in the nasopharynx, and 40 in more than one site. Overweight (BMI 25-30) was associated with a decreased risk of the overall head and neck cancer incidence (HR: 0.83; 95%CI 0.70-0.97). Among never-smokers, total head and neck cancer incidence was not associated with BMI, while in ever-smokers, having a BMI over 35 was associated with a lower risk (HR: 0.42; 95%CI: 0.21-0.83), adjusted for the number of past and current cigarettes smoked. Oro-and hypo-pharyngeal cancers showed an increased risk among lean people (BMI&lt; 18.5 versus normal; HR: 4.32; 95CI: 1.53-12.18). For oro- and hypo-pharyngeal cancers, leanness increased the risk both in ever and never-smokers. Waist circumference and waist-to-hip ratio did not show significant associations with any of the cancer sites studied.
Conclusion: This is the first prospective study to show that overall (but not abdominal) obesity was associated with a lower risk of incident head and neck cancers, especially among smokers. Risk of oro- and hypopharyngeal cancers showed an inverse association with BMI, irrespective of smoking habits, which may be due to their stronger link to HPV infection rather than smoking.
Citation Format: Arash Etemadi, Mark G. O'Doherty, Neal D. Freedman, Albert R. Hollenbeck, Sanford M. Dawsey, Christian C. Abnet. A prospective cohort study of body size and risk of head and neck cancers in the NIH-AARP Diet and Health Study. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2529. doi:10.1158/1538-7445.AM2013-2529