Weight and pressure ulcer occurrence: a secondary data analysis.

BACKGROUND Prolonged external mechanical loads lead to compression, tension and shear of the skin and underlying tissues leading to pressure ulcers. Underweight seems to be associated with high pressure ulcer risk but the distinct relation between overweight and pressure ulcer development is uncertain. Anatomical and physiological differences of typical pressure ulcer points are often neglected. OBJECTIVES (1) Is there a relationship between BMI and superficial (category 2) and deep (category 3/4) pressure ulcers on the trunk? (2) Is there a relationship between BMI and superficial (category 2) and deep (category 3/4) pressure ulcers at the heels? DESIGN Secondary data analysis of ten pressure ulcer prevalence surveys in Germany. Comparison of proportions of pressure ulcer patients according to the 12 BMI groups provided by the WHO considering superficial and deep pressure ulcers and different anatomic locations. SETTING AND SAMPLE Hospital patients (n=50,446). Median age was 68 (IQR 55-78) years and the proportion of female patients was 55.4%. RESULTS The overall proportion of patients with at least one pressure ulcer at the trunk was 2.0% (99% CI 1.8-2.2) for category 2 and 0.9% (99% CI 0.8-1.0) for category 3/4 pressure ulcers. Trunk pressure ulcer proportions were significantly higher in thin individuals than in normal weight and obese patients. The overall proportion of patients with at least one heel pressure ulcer was 0.6% (99% CI 0.5-0.7) for category 2 and 0.6% (99% CI 0.5-0.7) for category 3/4. With one exception there were no statistically significant differences between BMI groups. CONCLUSIONS Irrespective of the degree of mobility and activity thin patients are at higher risk for pressure ulcers at the sacrum, ischial tuberosity, trochanter and shoulder than normal weight and obese patients. Heel pressure ulcers seem to be unrelated to the BMI level, indicating that the BMI is not a predictor for heel PU development. These results also support the assumption that the etiology and pathogenetic mechanisms of trunk and heel PU development might be partially different. Pressure ulcer risk models might need to be redesigned because distinct risk factors only apply to distinct anatomic locations.