Body mass index and persistent pain after breast cancer surgery: findings from the women's healthy eating and living study and a meta-analysis.

The purpose of this study is to evaluate the association between body mass index (BMI) and persistent pain after breast cancer surgery in a prospective study and synthesize available evidence through a meta-analysis. In the Women's Healthy Eating and Living (WHEL) Study, 3,088 women diagnosed of breast cancer were enrolled and assessed. After 4 years, a subgroup of 2,131 women was re-assessed for the pain information. Logistic regression models were used to assess the associations of baseline BMI and BMI change between baseline and 4 years of follow-up with general pain symptoms at 4 years of follow-up. We further synthesized all available evidence from observational studies by searching PubMed and Embase up to February 2017. In the WHEL study, baseline BMI was linearly associated with an increased risk of persistent pain at 4 years of follow-up (odds ratio (OR) (95% confidence interval (CI)): 1.07 (1.05-1.10)). After adjusting for baseline BMI, BMI change since baseline was associated with persistent pain (OR (95% CI) for every unit increase: 1.10 (1.04-1.16)). After searching the literature, additional eight studies were eligible to be included in the meta-analysis. After pooling estimates from all nine studies, there was a positive association with persistent pain development comparing obesity or overweight with normal weight. Available data suggested a linear relationship between BMI and persistent pain (OR (95% CI) for every one unit increment of BMI: 1.04 (1.02-1.07)). Overall, our analyses suggested that BMI might be positively associated with risk of persistent pain after breast cancer surgery.