Forgoing care because of costs is a frequent situation in many countries, with estimated prevalences going from 4% to 30% [1][2][3][4][5][6]. It can be defined as a decision of not seeking care when needed because of financial reasons and the term is used interchangeably with unmet needs as both terms provide similar information [7]. Whereas most studies on the prevalence of forgoing care because of costs target the general populations, little is known of the prevalence of forgoing care for people with specific chronic conditions. The few studies exploring this issue reported a prevalence close to general population figures [5,[8][9]. As people with chronic conditions have a high demand of health care, such prevalence may either be lower, since they are being followed by a health practitioner and are already navigating the system, or on the contrary, may be similar or higher, since they might decide to prioritize some health issues at the expense of other conditions.Our main objective was to assess the prevalence of forgoing care because of costs in Swiss patients with diabetes; a secondary objective was to explore whether forgoing care because of costs was related to a risk of worsening the quality of their care after three years of follow-up.We used data from a prospective Swiss cohort study, the CoDiab-VD cohort, consisting of non-institutionalized adults with a diagnosis of diabetes of at least one-year duration and residing in the canton of Vaud (≈ 750'000 inhabitants). Participants were recruited in 2011-2012 by community-based pharmacies and are followed-up yearly [10]. Study data were collected from paper-based questionnaires sent to participants' home. All variables, described in details elsewhere [10], are briefly presented thereafter. The primary exposure variable of the study was forgoing care because of costs at baseline, 3 measured using the following question: "During the last twelve months, did you forgo any type of care because of the costs you would have to pay?" Participants were considered to have forgone care during the past 12 months if they answered "yes" to that question. We considered eight diabetes-specific processes of care (e.g. HbA1c control, annual foot examination) and five outcomes of care (e.g. mean HbA1c, generic and disease-specific health-related quality of life) as dependent variables, and other covariates (e.g. age, gender, socio-demographics) [10]. The prevalence (and 95% confidence interval) of forgoing care and the type of care forgone were calculated.Then, bivariate analyses were conducted to compare participants forgoing vs not forgoing care. Finally, crude and adjusted mixed logistic and linear regression models were used to assess the over time effect of forgoing care on the dichotomous and continuous processes and outcomes of care indicators, respectively.At baseline, results showed a prevalence of persons reporting having forgone care because of costs of 15.7% (95% CI 12.5%-18.9%), with dental (9.7%) and foot (5.2%) care most often reported to have been forgone (oth...