Long-Term Trends in the Use of Complementary and Alternative Medical Therapies in the United States

Community surveys done over the past decade have documented that a substantial proportion of Americans use complementary and alternative medical (CAM) therapies (14), which have been defined as interventions neither taught widely in medical schools nor generally available in U.S. hospitals (1). Many managed care organizations have responded to this evidence by providing insurance coverage for some CAM therapies (5). Furthermore, most U.S. medical schools have begun offering courses on CAM therapies (6). These responses imply that CAM therapies are perceived to be a force to be reckoned with for some time to come. Yet, little is known about the likelihood that this will be the case. The prevailing assumption is that CAM therapies were used by a fairly narrow segment of the population until the 1970s, at which time the ideology associated with the youth counterculture led to a rapid dissemination and use of CAM therapies that has persisted through the present (7). However, lack of rigorous trend data from epidemiologic surveys have precluded evaluating this assumption rigorously or projecting the future growth of CAM therapies on the basis of evidence of past trends. In the current report, we present nationally representative trend data of this sort from a prevalence study. The data came from retrospective self-reports of a nationally representative sample of the U.S. general population in a 19971998 telephone survey (4) about age at first use of 20 representative CAM therapies. In our analysis, we studied trends by examining between-cohort differences in rates of initiation of CAM therapy use (8). In the absence of prospective data, which do not exist, our results represent, to our knowledge, the most accurate information currently available on U.S. trends in CAM therapy use over the past half-century. Methods Sample The telephone survey was conducted between November 1997 and February 1998 in a nationally representative household sample. Random-digit dialing was used to select households, and a random-selection method was used to select one respondent 18 years of age or older for interview in each sample household. Eligibility was limited to English speakers without cognitive or physical impairment that would prevent interview completion. The average administration time was 30 minutes. A $20 financial incentive for participation was offered. The Beth Israel Deaconess Committee on Clinical Investigations, Boston, Massachusetts, approved the survey methods. Of the initial sample of 9750 telephone numbers, 26% did not work, 17% were not assigned to households, and 9% were unavailable despite six attempted follow-up contacts. Of the remaining households, 481 were ineligible because of language barrier or cognitive or physical incapacity. Of the 4167 total eligible respondents, 1720 (41.3%) completed the interview on initial request. Of a random subsample of 1066 persons who initially declined and were offered an increased stipend ($50), 335 agreed to participate. In all, 2055 interviews were completed. After we extrapolated the conversion rate to all persons who had initially declined and weighted the data for the undersampling of those who participated after initially declining, the weighted overall response rate among eligible respondents was 60%. The data were weighted for three factors: 1) probability of selection within household as well as geographic variation in cooperation (by region of the country and urbanicity [local population density]], 2) nonresponse, and 3) post-stratification for aggregate discrepancies between the sample distributions and Census population distributions on a variety of sociodemographic variables (9, 10). More details on the sample design have been presented elsewhere (4). Age data were missing for 6 respondents; our analyses are limited to the remaining 2049 respondents. Measures The interview was described to respondents as a survey by investigators from Harvard Medical School about the health care practices of Americans. Interviewers made no mention of CAM therapies. The first substantive questions concerned perceived health, functional impairment due to health problems, interactions with physicians, and history of chronic medical conditions. Interviewers then queried respondents about their lifetime and recent use of 20 CAM therapiesacupuncture, aromatherapy, biofeedback, chiropractic care, commercial diet programs, energy healing (for example, laying on of hands), folk remedy, herbal medicine, homeopathy, hypnosis, imagery, lifestyle diet (such as vegetarianism or macrobiotics), massage, megavitamin therapy, naturopathy, osteopathy, relaxation techniques, self-help group, spiritual healing by others, and yoga. Users of each therapy were asked their age at first use as well as details about the conditions for which the therapy was initiated. The final set of questions dealt with sociodemographic issues. Cohorts were aggregated into three subsamples: prebaby boom (respondents 54 years of age at interview, born before 1945); baby boom (34 to 53 years of age at interview, born 19451964); and postbaby boom (18 to 33 years of age at interview, born 19651979). For sociodemographic variables, we used two categories for sex (male or female), four for race/ethnicity (non-Hispanic white, non-Hispanic black, Hispanic, or other), four for education (less than high school, high school graduate, some college, or college graduate), four for U.S. region (northeast, midwest, south, or west), and four for urbanicity (residence in a large city, small city, suburb, town/rural). Statistical Analysis All analyses were performed with weighted data by using SAS statistical software (11). To assess differences in trends among cohorts, the KaplanMeier (12) method was used to generate a graphic representation of the cumulative lifetime prevalences of CAM therapy use according to cohort. The significance of historical changes in lifetime use was estimated by using discrete-time survival analysis (13), a method of survival analysis appropriate for data in which events are recorded only at discrete time points (for example, in yearly increments). Discrete-time survival analysis was operationalized as a logistic regression with person-year as the unit of analysis and first use of CAM therapy as the outcome variable. The predictors of primary interest were a series of dummy variables for decades of historical time, and covariates included sociodemographic and dummy variables adjusted for the baseline hazard rate of each year of a person's life. This model results in an intercept for each time period, and the odds ratios (ORs) can be interpreted as the relative risk for the annual risk for use of alternative therapy. Subsample models were estimated to study sociodemographic variation in trends. Disaggregated models were estimated to study trends in the use of particular CAM therapies. To adjust for the design effects introduced by weighting of the data, the method of jackknife repeated replications (14) was used to estimate standard errors (SEs). For this method, we used user-written macros in SAS statistical software. For this process, 50 random primary sampling units were created with two random half-samples in each unit for a total of 100 random replicates. Jackknife repeated replication is a method that uses simulations of coefficient distributions in subsamples to generate empirical estimates of SEs and significance tests. The ratios of the coefficients to these adjusted SEs are used to compute the 95% CIs of the ORs. Tests for the significance of sets of predictors taken together were computed by using the Wald chi-square test from coefficient variancecovariance matrices based on the jackknife repeated replications simulations. Results Differences in Aggregate Use Trends among Cohorts At the time of interview, 67.6% of all respondents had used at least one CAM therapy at some time in their lives. The Figure presents KaplanMeier age-of-onset curves showing trends in each cohort in the cumulative probabilities of use according to age. Of note are the dramatic differences in use among cohorts. This is seen most clearly by focusing on cumulative probabilities of use for age 33 years, the oldest age represented in all three cohorts. Approximately 3 of every 10 respondents in the prebaby boom cohort used some type of CAM therapy by the age of 33 years compared with 5 of 10 in the baby boom cohort and 7 of 10 in the postbaby boom cohort. Figure. Weighted KaplanMeier estimates of age of first use of any complementary and alternative medical (CAM) therapy among lifetime users according to cohort. Historical Trends in Aggregate Use The aggregate data in the Figure are presented in a different format in the bottom row of Table 1, where the risk ratios are shown from a discrete-time survival model that estimated the effects of historical time in predicting age at first use of CAM therapy among respondents after adjustment for person-year and sociodemographic variables. The contrast category is first use before 1960. Consistent with the pattern in the Figure, the results of the model for the outcome of any therapy show monotonically increasing risk ratios in each decade from the 1960s through the 1990s. Table 1. Trends in Relative Risk for First Use of 20 Specific Complementary and Alternative Medical Therapies, according to Decade Possible demographic subsample differences in time trends were examined by estimating separate subsample models that were identical to the discrete-time survival model for any therapy and by evaluating the statistical significance of differences in trends across subsamples. No statistically significant (0.05 level in two-sided tests) differences in trends were found for sex, race/ethnicity, education level, region of the country, or urbanicity. Trends in the Use of Specific Therapies Table 1 also shows the risk ratios to estimate first use of each of the 20 CAM therapies assessed. All tre