A host of other factors may also contribute to any given individual's risk of DCS. Some probably play minor roles, and some potentially play important roles that have not yet been fully defined. Nutritional status, for example, plays a major role in one's general health and often in one's physical fitness, too. While research on the subject of nutrition and diving is limited, it is possible that it also affects decompression safety. For example, one study assessed the relationship between cholesterol levels and decompression-induced bubbles. Doppler ultrasound was used to classify the 30 subjects as either "bubble-prone" or "bubble-resistant." Among the study's findings was that, on average, bubble-prone subjects had higher total blood cholesterol levels than the bubble-resistant subjects (Webb et al. 1988). Additional research into this and many other areas is needed.