Although studies on nonadherence to ART are common, one strength of this analysis is the use of probability sampling methods, which resulted in coverage of patients from 582 medical facilities in 19 U.S. states and Puerto Rico. The use of ART was high among adults in care for HIV. The persons not receiving ART were more likely to be female, to be black, and to report a lapse in health coverage, substance use, higher VL results, higher CD4 count as the nadir, and more frequent feelings of depression. Our findings agree with those in other reports [19
]. Understanding factors associated with use of ART may inform efforts to increase appropriate ART among HIV-infected persons.
Nonadherence to ART was substantial. Reported nonadherence during the past 48 hours ranged from 13% to 30%, depending on which measure was examined; 38% were nonadherent to at least one measure. We found a direct relationship between a detectable VL and each of the three measures of nonadherence. The association increased with the number of measures to which a patient was nonadherent, indicating the clinical importance of assessing multiple dimensions of nonadherence. Our findings are consistent with those reported previously [10
], but there have been few studies comparing dose, schedule, and instruction nonadherence, so further examination of the impact of different measures of nonadherence on clinical outcomes is warranted.
Although predictors of the three measures of nonadherence varied, younger age and binge drinking were consistently associated with poorer adherence. Like other researchers [26
], we found associations between younger age and multiple measures of nonadherence. Lifestyle differences, decreased awareness of mortality and thus motivation to care for one’s health, and a survivor effect have been proposed as reasons for poorer adherence among younger HIV-infected persons [27
]. Measured in various ways, alcohol use has consistently been associated with nonadherence [28
]. We found that binge drinking was strongly associated with all three measures of nonadherence. Others have found that the quantity of alcohol ingested was more important in predicting nonadherence than was the frequency of use [29
]. Taken together, these findings suggest that HIV care providers should ask patients about both the frequency and the quantity of alcohol consumed. When a patient acknowledges binge drinking, the provider should explain how binge drinking affects ART adherence and other health behaviors. Such conversations could help HIV care providers identify patients who need more intensive counseling about adherence and substance use. Few effective interventions have addressed problem drinking among HIV-infected persons [31
], and the effects of the small number of trials on adherence among problem drinkers have not been sustained [32
]. The limited evidence suggests that adapting adherence interventions to persons with alcohol problems may be challenging [31
]. Our results underscore the need to develop effective adherence interventions for problem drinkers, which potentially could have positive effects on all aspects of adherence.
Black and Hispanic race/ethnicity, female gender, receipt of public assistance, feeling depressed, and number of daily ARV doses were also independently associated with poorer adherence for at least two of the three measures of nonadherence. Several recent studies have found that race/ethnicity is independently associated with nonadherence [17
]. Race/ethnicity may also be a proxy for factors associated with nonadherence, such as differences in trust of physicians [36
] or HIV conspiracy beliefs (e.g., the belief that HIV was created by the U.S. government to perpetrate genocide against blacks) [37
]. Recent studies indicate that disparities in health literacy and numeracy skills, which we were not able to measure, may also be important mediators of the relationship between race and medication management [38
Similar to findings regarding adherence to treatment for chronic diseases such as diabetes [40
], published descriptions of the effect of gender on ART adherence in the scientific literature have been mixed; some studies find women more likely to be nonadherent [41
], and others find no difference by gender [43
]. Our finding suggests gender may influence some, but not all, dimensions of medication-taking behavior (dose and schedule nonadherence, but not instruction nonadherence). Another possible explanation for the observed gender differences is that other factors affecting nonadherence, such as alcohol or drug use, may differ for men and women [44
]. Additional factors we were not able to measure, such as numeracy skills [45
], may also mediate the relationship between gender and nonadherence.
Our finding that the frequency of feelings of depression was associated with dose and instruction nonadherence to ART is consistent with other studies [46
]. This association reinforces the importance of active screening for depression among HIV-infected persons [48
]. Studies have suggested that training in stress management [49
] and prescription of antidepressant medications [50
] may improve adherence in this population.
Our finding that nonadherence increases as the daily ARV dose increases agrees with published results [51
]. Airoldi and colleagues found that switching to a single-pill regimen improved adherence [53
]. Although some ART regimens are less susceptible to nonadherence than others [9
], our findings suggest that simplifying ART regimens by decreasing dosing frequency would improve adherence.