Participation and adherence among older men and women recruited to the Beta-Carotene and Retinol Efficacy trial (CARET)

Our plain-English summary of Participation and adherence among older men and women recruited to the Beta-Carotene and Retinol Efficacy trial (CARET), by M.D. Thornquist, D.L. Patrick, G.S. Omenn (The Gerontologist, 1991).

The study

• Authors: M.D. Thornquist, D.L. Patrick, G.S. Omenn
• Journal: The Gerontologist
• Published: 1991;31(5):593-7
• Cited by: 17 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

We evaluated as functions of age and gender participation and adherence rates in older adults recruited to pilot studies for CARET, a multicenter chemoprevention trial. Eligible were men and women aged 50-69 who were current or recent former smokers, and men aged 45-74 with occupational exposure to asbestos. We found negligible differences by age in response to recruitment mailings, drop out during the enrollment process and after randomization, and adherence to taking the study capsules. Men had numerically lower drop-out and higher adherence rates than women, but differences were not statistically significant. These results should encourage researchers to recruit older men and women (at least up to age 69) to clinical trials.

In plain English

This article reported how age and sex related to participation and adherence in two pilot studies from 1985 to 1988 for CARET, a trial of beta-carotene and retinol capsules against lung cancer. One pilot recruited 1,000 men with extensive occupational asbestos exposure, eligible if aged 45 to 74 at randomization (816 randomized). The other recruited 1,284 male and female heavy smokers, eligible if aged 50 to 69 at randomization (1,029 randomized). Among asbestos-exposed workers, 18% dropped out during the two-month enrollment period. Drop-out was lowest, 13% to 15%, at ages 55 to 69. After randomization, age had no statistically significant effect on drop-out in either study. Among asbestos-exposed workers, the share of visits attended differed significantly by age. It was highest at ages 55 to 59 (77%) and lowest at ages 45 to 49 (69%) and 70 to 74 (71%). Among smokers, men attended 74% of visits and women 70%. Age had no statistically significant effect on how many capsules participants took. The authors concluded that the results were reassuring about older people's willingness to take part in prevention trials.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Analysis of participation and adherence by age and sex within two pilot randomized, double-blind chemoprevention studies for CARET
• Who was studied: The first pilot recruited 1,000 men with occupational asbestos exposure (816 randomized) between 1985 and 1988. They were recruited through mailings to workers' compensation programs, physicians, attorneys and unions, and were eligible if aged 45 to 74 at randomization; six were 44 at their first visit. The second pilot recruited 1,284 male and female heavy smokers (1,029 randomized, 48% female) through mailings to insurees of Seattle-based King County Medical Blue Shield. They were eligible if aged 50 to 69 at randomization; eight were 48 or 49 at their first visit.
• Exposure: The asbestos-exposed men had extensive occupational asbestos exposure in high-risk trades. To be eligible, their first exposure had to be at least 15 years before randomization. They also needed either 5 years in a high-exposure trade or chest x-ray abnormalities consistent with asbestosis. In the study, they were randomized to 15 mg/day of beta-carotene plus 25,000 IU/day of retinol, or to placebo. Fiber types were not named.
• Main results:
  • Heavy smokers: 4.3 enrolled per 100 recruitment letters overall. By age, rates were 3.9 per 100 (50-54), 4.9 (55-59), 4.7 (60-64) and 3.2 (65-69). These small differences were statistically significant (p = .005).
  • Asbestos-exposed workers: overall drop-out during the 2-month enrollment period was 182 of 993 (18%). Rates were lowest in the 55-69 age range at first visit (13%, 13%, 15%). They were higher at 45-49 (21%), 50-54 (25%) and 70-74 (24%), with p = .05.
  • Heavy smokers: enrollment drop-out did not vary statistically by age or sex (males 133 of 671, 20%; females 116 of 602, 19%). Among women, drop-out rose with age.
  • After randomization, age had no statistically significant effect on drop-out in either study, and sex had none among smokers. Drop-out was numerically higher in the youngest and oldest participants and in females.
  • Asbestos-exposed workers: visit attendance was significantly associated with age (p = .03). It was highest at 55-59 (77%) and lowest at 45-49 (69%) and 70-74 (71%).
  • Heavy smokers: age had no statistically significant effect on visit attendance (p = .12). Men attended 74% of visits and women 70% (p = .003).
  • Age had no statistically significant effect on mean capsule consumption, which was lowest in the youngest and oldest participants in each study. Among smokers, men took 85% of their capsules and women 82% (p = .06).
• The authors' conclusion: The authors concluded that participation and adherence were essentially similar across 5-year age groups. They found the results reassuring about the willingness of older people (up to ages 65-69 for smokers and 70-74 for asbestos-exposed workers) to take part in randomized prevention studies.
• Limitations the authors state:
  • Response to recruitment mailings could be measured only for smokers. Asbestos-exposed workers often got letters from several sources, and some mailings were sent by third parties who did not share recipient names.
  • Figures for the 32- and 36-month visits came from very small numbers of participants and are the least reliable.
  • The authors did not expect to be able to test whether employment status explained the sex difference, because follow-up data on inactive participants are hard to obtain.

Topics

Medical terms in this study, explained in our Lexicon: Occupational Exposure, Clinical Trial.

Related studies

• CARET, the beta-carotene and retinol efficacy trial to prevent lung cancer in asbestos-exposed workers and in smokers — G.S. Omenn, G. Goodman, et al. (1991)
• Research cost analyses to aid in decision making in the conduct of a large prevention trial, CARET. Carotene and Retinol Efficacy Trial — M.D. Thornquist, N. Urban, et al. (1993)
• Risk factors for lung cancer and for intervention effects in CARET, the Beta-Carotene and Retinol Efficacy Trial — G.S. Omenn, G.E. Goodman, et al. (1996)
• Recruitment for the beta-carotene and retinol efficacy trial (CARET) to prevent lung cancer in smokers and asbestos-exposed workers — G.S. Omenn, G. Goodman, et al. (1992)
• Changes in cholesterol and triglyceride concentrations in the Vanguard population of the Carotene and Retinol Efficacy Trial (CARET) — B. Cartmel, J. Dziura, et al. (2005)
• Lobe of origin and histologic type of lung cancer associated with asbestos exposure in the Carotene and Retinol Efficacy Trial (CARET) — C.A. Brodkin, J. McCullough, et al. (1997)

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