|
Article Excerpt
Diabetes mellitus (DM) prevalence is rising (Mokdad et al. 2000; Bagust et al. 2001). Adherence of diabetes patients to recommended care can markedly reduce complication rates. In the U.K. Prospective Diabetes Study (UKPDS), fight blood glucose control and biannual monitoring lowered the microvascular complication risk by 25 percent (UKPDS Group 1998). Recommended care includes following regimens for prescribed medications, diet and exercise, and screenings, including HbA1C testing, lipid profiles, and eye exams, conducted at least annually. Diabetes outcomes appear to be more closely related to patient characteristics and decisions than to characteristics of patients' physicians or clinics (Glasgow et al. 1997; Heisler et al. 2003a; O'Connor et al. 2008).
Rates of actual use of care fall far short of recommended DM care levels. McGlynn et al. (2003) reported that 45 percent of DM-diagnosed persons in this U.S. study followed recommended care. Some other studies have found higher rates (Harris 1996; Lin et al. 2004), but overall, there is considerable variability in findings (Kell et al. 1999; Cramer 2004). Some results suggest a secular trend toward greater conformance between actual and recommended DM care (Puent, Nichols, and Scarborough 2005), but there is also contrary evidence (Sequist et al. 2006). Frequent physician visits do not assure that persons diagnosed with DM follow care recommendations. Health care providers may fail to abide by the DM care recommendations either by not providing particular services or failing to stress the importance of diabetes self-management to their patients (Sloan et al. 2004; Keating et al. 2007).
We used data from a special survey of DM-diagnosed persons, who had responded to previous waves of the Health and Retirement Study (HRS), a longitudinal database. The special cross-sectional survey, the HRS-Diabetes Study (HRS-DS), is unique in providing information on preferences and beliefs that may affect rates of utilization of care and behaviors relative to recommendations for persons diagnosed with DM and laboratory findings on respondents' HbA1c levels.
Our study assessed relationships between risk tolerance and time preference, self-assessed control over life events, subjective beliefs about longevity, and socioeconomic factors on (1) use of services and behaviors recommended for persons with a diagnosis of DM and (2) subjective and objective measures of diabetes control and health. The contribution of this study is first in its empirical analysis of the roles of preferences and beliefs in utilization decisions and on health outcomes, including a laboratory-based finding among persons with a chronic disease that is both common and becoming more so. Second, we account for differences in many factors, including insurance status, income, and preferences and beliefs, and still find disparities based on race/ethnicity in health outcomes but not health inputs.
DECISIONS ABOUT CARE FROM THE INDIVIDUAL'S PERSPECTIVE
In Grossman's (1972) health capital model, individuals demand a commodity, "good health," both because there is positive utility associated with being healthy, and having good health determines the amount of time available for home and income production. Health capital in any period equals undepreciated health stock from the last period and gross health investment. Individuals can increase or maintain their stock of health capital through investments in medical care and time spent engaging in health-producing activities. An individual's allocation of time depends on time and money prices. One implication of the model is that the amount of time and income devoted to health investment depends on an individual's perception of the effect of current health investment on future health. A person with a high degree of self-efficacy is thus more likely to undertake health investment. People who face competing risks of death are expected to invest less in their health (Dow, Philipson, and Sala-I-Martin 1999). More time-impatient persons are expected to invest less as are more risk-tolerant persons. Higher income increases willingness to pay for good health (Viscusi and Evans 1990). Because it lowers the price of care, being insured should increase use of personal health care services.
In our empirical analysis, both inputs affecting health investment and health outcomes were considered to be endogenous. We estimated reduced form equations for health inputs and health outcomes. We did not attempt to analyze the effect of health inputs on health outcomes, that is, estimate a health production function, because each of the health inputs is endogenous to health outcomes. Individuals who invest more in controlling their diabetes may be healthier or believe they can affect outcomes better. Proper estimation of a health production function would require a panel of outcome data sufficient to estimate changes in health over time, which we do not have for most of our measured outcomes.
METHODS
Data
Data were obtained from the HRS and the 2003 HRS Diabetes Study (HRSDS). The HRS is a longitudinal national panel study beginning in 1992 with the main respondents being persons born during 1931-1941 and their spouses who could be of any age; spouses received the same interview as main respondents. The HRS over-samples blacks, Hispanics, and Florida residents, but otherwise it is representative of the U.S. population of this age. In 1998, HRS was combined with another panel survey, Aging and Health Dynamics among the Oldest Old (AHEAD), which surveyed persons born in 1923 and earlier. Also in 1998, an additional sample from the 1942-1948 birth cohort was added. Our study uses data on demographic characteristics, cognitive status, general health status, income, and beliefs about longevity from HRS interviews conducted in 2002.
The HRS-DS, conducted by mail, provides additional clinical information, including self-reports of DM care, use of prescribed medications, health behaviors, preferences, and perceived control of DM. The HRS-DS obtained the respondent's HbA1c levels, as determined by an independent laboratory.
The sample selection process was as follows: 3,194 HRS respondents had reported a DM diagnosis by the 2002 HRS interview. Of these, 680 were excluded because the respondent had participated in a prior HRS special survey. There were 129 2002 HRS respondents who died before the 2003 HRS-DS and 484 persons who did not return the HRS-DS questionnaire, leaving a sample of 1,901 (79 percent response). Valid HbA1c blood spot assays were not returned from 668 HRS-DS respondents, yielding 1,233 valid HbA1c values. Eliminating persons over age 92 reduced the analysis sample to 1,530 and to 1,034 for the HbA1c analysis.
EMPIRICAL SPECIFICATION
Dependent Variables
Individual's Use of Recommended Care and Practices. We constructed a summary measure of the respondent's use of care and practices recommended by the American Diabetes Association Clinical Practice Recommendations for 2003 (American Diabetes Association 2003). Our index was based on self-reported information from the HRS-DS on whether during the last year the respondent's (1) HbA1c and/or (2) cholesterol was tested; (3) the person received an eye examination; (4) the person tried to lose weight or the person had a Body Mass Index (BMI) of 25 or less at the 2002 HRS interview; (5) s/he engaged in any type of regular exercise; (6) and whether s/he "rarely" or "never" missed taking a...
|
