Body mass index trends and quality of life from breast cancer diagnosis through seven years' survivorship

Abstract

Background: Weight gain is a potential negative outcome of breast-cancer treatment, occurring in 50%-to-96% of breast-cancer patients, although the amount of weight gain is inconsistently reported in the literature. Research has also shown a relationship between overweight/obesity and breast-cancer mortality. Correspondingly, weight management is a self-care approach known to benefit quality of life (QOL). These research questions and analysis add to existing literature by examining participants' body mass index (BMI) trend and its relationship with QOL indicators over seven years.

Aim: To examine: (1) BMI trends among breast cancer survivors; and (2) The trends' relationship to QOL indicators over seven years.

Methods: During the Breast Cancer and Lymphedema Project, 378 patients' weight and height were recorded by nurses prior to or just after beginning breast cancer treatment and repeated at quarterly-to-semiannual intervals over seven years. Additionally, participants annually completed the 36-Item Short Form Health Survey (SF-36), a valid and reliable tool assessing QOL and health concepts, including physical function, pain, and emotional well-being. BMI trends, change in BMI, and change in SF-36 subscales over seven years were calculated using a random-intercept repeated-measures regression. Patients were placed into BMI categories at each time point: Normal, Overweight and Obese. As patients' weights changed, they were categorized accordingly.

Results: During the seven-year study and while controlling for age and residence, participants gained an average of 0.3534 kg/m² (P = 0.0009). This amount remained fairly consistent across BMI categories with those in the normal-weight category (n = 134) gaining 0.4546 kg/m² (P = 0.0003); Overweight (n = 190) gaining 0.2985 kg/m² (P = 0.0123); and obese (n = 199) gaining 0.3147 kg/m², (P = 0.0649). Age (under or over 55) and region (metro/micro vs small/rural) were significantly associated with BMI increase in both the normal and obese categories. There were statistically significant (P < 0.0100) changes in five of the eight SF-36 domains; however, the directions of change were different and somewhat divergent from that hypothesized. Controlling for age and region, these five were statistically significant, so there were no change or differences between the micropolitan/metropolitan and small town/rural groups.

Conclusion: Although only modest increases in mean BMI were observed, mean BMI change was associated with selected QOL indicators, suggesting the continued need for self-care emphasis during breast cancer survivorship.

Keywords: Breast cancer; Breast cancer treatment effects; Quality of life; Survivorship.

Figure 1

Normal body mass index trends over time comparing age group and region. The estimated body mass index (BMI) trajectory for four women whose BMI falls in the normal range are shown in this graph. They all started with a BMI of 23, a weight of 134 lbs and height of 5’4. The model is designed so the reference groups were ≥ 55 years old and a living in a small town or rural region. A woman falling into these two groups is represented by the solid black line (average expected gain in BMI of 0.45kg/m²).

Figure 2

Overweight body mass index trends over time comparing age group and region. The estimated body mass index (BMI) trajectory for four women whose BMI falls in the overweight range are shown in this graph. They all started with a BMI of 27, a weight of 158 lbs and height of 5’4. The model was designed so the reference groups were ≥ 55 years old a living in a small town or rural region. A woman falling in these two groups is represented by the solid black line (average expected gain in BMI of 0.30 kg/m²).

Figure 3

Obese body mass index trends over time comparing age group and region. The estimated body mass index (BMI) trajectory for four women whose BMI falls in the obese range are shown in this graph. They all started with a BMI of 33, a weight of 192lbs and height of 5’4. The model was set up so the reference groups were ≥ 55 years old a living in a small town or rural region. A woman falling in these two groups is represented by the solid black line (average expected gain in BMI of 0.31 kg/m²).