The Correlation between Body Mass Index and Breast Cancer Risk or Estrogen Receptor Status in Okinawan Women

Abstract

Dietary changes resulting from the post-World War II occupation of Okinawa by the US military have been largely deleterious, resulting in a marked increase of obesity among Okinawan residents. In this study, we examined the association between BMI and the risk of developing breast cancer according to the menstruation status and age, and the correlation between BMI and expression of estrogen receptor (ER). Breast cancer cases were 3,431 females without any personal or family history of breast cancer. Control subjects were 5,575 women drawn from the clinical files of Nahanishi Clinic. We found that women, who were overweight or obese, regardless of menopausal stage, had a higher risk of breast cancer compared to women with normal weight and this difference was statistically significant (p < 0.001, respectively). This risk was especially apparent in older (> 40 years) overweight or obese women. The women who were overweight or obese during postmenopausal ages were at higher risk of ER-positive breast cancer compared to women with normal weight. Results of our present study clearly indicate that increased BMI was associated with increased risk of developing breast cancer in Okinawan women, regardless of menopausal status. In addition, there was statistically significant correlation between BMI and ER expression in the postmenopausal period. Given the obesity epidemic associated with the extreme sociological and dietary changes brought about by the post-war occupation of Okinawa, the present study provides essential guidelines on the management, treatment and future breast cancer risk in Okinawa.

Elevated Serum Levels of Heat Shock Protein 70 Are Associated with Breast Cancer

“…As previous studies indicated that increased BMI was associated with the increased risk of BC in Okinawa (Tamaki et al 2014), we wanted to determine whether there was an association between HSP70 and obesity. Therefore we divided patients into two subgroups, according to BMI above (obese) or below (non-obese) 30 kg/m 2 (World Health Organization 2011).…”

Can We Improve Breast Cancer Mortality in Okinawa? : Consensus of the 7th Okinawa Breast Oncology Meeting

“…The introduction of the US lifestyle and diet to people of Okinawa is generally considered the simplest and most plausible explanation of the clearly documented loss of longevity advantage among younger generations of Okinawan people (Todoriki et al 2004;Willcox 2005;Tamaki et al 2013). We reported on the correlation between BMI and breast cancer risk for Okinawan people and in particular increased risks associated with the marked increment of BMI since US military occupation in our previous study (Tamaki et al 2014). Results of this study demonstrated that the Okinawan women who were overweight and/or obese during premenopausal and postmenopausal ages had a statistically significant higher risk of breast cancer development compared to those with non-overweight and/or obese women (Tamaki et al 2014).…”

“…Results of this study demonstrated that the Okinawan women who were overweight and/or obese during premenopausal and postmenopausal ages had a statistically significant higher risk of breast cancer development compared to those with non-overweight and/or obese women (Tamaki et al 2014). The Okinawan people have adjusted to low calorie environment for more than a millennium in a rather isolated island environment (Tamaki et al 2014). Thus, this increment of breast cancer development in Okinawan women following World War II might be explained by the introduction of an US style diet as a result of the US military occupation, oversaturation by lipids and cholesterol of the liver clearance system of estrogen in Okinawan overweight women, expose their system to much endogenous estrogen (Tamaki et al 2014).…”

“…We reported on the correlation between BMI and breast cancer risk for Okinawan people and in particular increased risks associated with the marked increment of BMI since US military occupation in our previous study (Tamaki et al 2014). Results of this study demonstrated that the Okinawan women who were overweight and/or obese during premenopausal and postmenopausal ages had a statistically significant higher risk of breast cancer development compared to those with non-overweight and/or obese women (Tamaki et al 2014). The Okinawan people have adjusted to low calorie environment for more than a millennium in a rather isolated island environment (Tamaki et al 2014).…”

“…The Okinawan people have adjusted to low calorie environment for more than a millennium in a rather isolated island environment (Tamaki et al 2014). Thus, this increment of breast cancer development in Okinawan women following World War II might be explained by the introduction of an US style diet as a result of the US military occupation, oversaturation by lipids and cholesterol of the liver clearance system of estrogen in Okinawan overweight women, expose their system to much endogenous estrogen (Tamaki et al 2014). In addition, the peak ages of the age-adjusted incidence rates in Okinawa were 50-54 years old (61.8/100,000) in 1998, 55-59 years old (129.6/100,000) in 2003 and 65-69 years old (192.7/100,000) in 2008, respectively (Okinawa Prefectural Institute of Health and Environment 2014).…”