In a sample of 3,498 students living in two counties in California, each student's weight and backpack load were measured. Demographic information as well as information about backpack use was obtained. Nonspecific mechanical back pain was found to be highly prevalent, and the reported severity and chronicity of pain were high. Controlling for age, socioeconomic status, walking to and from school, and method of wear, results indicated that backpack weight, measured as a percentage of body weight, was effective in predicting back pain (P < 0.01). Girls and those who walk to and from school were more likely to report back pain (P < 0.01). The method of wear, socioeconomic status, and age were not found to be significantly related to the prevalence of back pain. However, with regard to the severity of pain, older age (P < 0.01), walking to and from school (P < 0.01), and method of wear (P < 0.05) were statistically significant.

We tested the assumption that there is a role reversal in exchanges of social support: that the older one becomes, the less likely one is to send support and more likely one is to receive it. Using data from a community study in Southern California with 513 middle-aged and older respondents, the results show that both support-sending and support-receiving decline with age. The respondents report giving more support than they receive until age 85+. Controls for income and activities of daily living extend the age at which role reversal occurs, and further controls for the number of people in the social network eliminate it. Examining different types of support and different sources of support shows that similar results apply to both affective and instrumental support, but that this pattern applies more to exchanges with family members, as all forms of role reversal are less likely in exchanges with nonfamily.

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