There is no age limit for methadone: a retrospective cohort study

The prevalence of opioid dependence is relatively stable in most European countries, including Switzerland, and currently stands at 0.1%-0.8% [1, 2]. Opioid dependence is a serious chronic condition that comes with a multitude of health and psychosocial risks and one which requires adequate long-term treatment [3‐5]. Based on decades of research, maintenance treatment with methadone or other suitable opioids, such as buprenorphine and slow-release morphine, is currently the mainstay of therapy for opioid dependence [6‐8]. Opioid maintenance is effective, well-tolerated and internationally accepted; it is also one of the most widely studied treatments for any disease [5, 9, 10]. Given adequate dosage and regular dosing, maintenance medication can prevent withdrawal symptoms, curb craving for heroin as well as other opioids and block their rewarding effects [8, 11, 12]. Maintenance treatment also substantially reduces health and psychosocial risks associated with illicit opioid use [13‐15]. Ideally, it would be a comprehensive treatment integrating medical care, psychosocial counselling and other services in which maintenance medication is prescribed to opioid-dependent persons without any undue restrictions [16, 17].

Since its inception over 45 years ago, hundreds of thousands of opioid users worldwide have benefited from methadone maintenance [5, 7]. While a new generation of opioid-dependent persons is entering treatment for the first time, at the other end of the age spectrum the population of older long-term patients continues to grow rapidly [18‐21]. This is largely due to the success of methadone programs in retaining patients in treatment and helping to prolong their lives--all that in spite of often complex and comorbid cases [20, 22‐25]. Furthermore, Arndt et al. recently found increasing proportions of patients aged older than 55 mentioning problematic heroin use when presenting for first-time treatment of substance use in the US [26].

There are many references in geriatric literature to methadone as it relates to the management of chronic and cancer pain. However, little information is available about opioid use and maintenance treatment in the elderly as well as their specific needs [20, 24, 25]. In addition, virtually no research addresses developments of the age structure of methadone populations. Among the exceptions are reports from the Addiction Treatment Forum. Data from "Beth Israel Healthcare System", New York City--the largest methadone program in the US with over 6,000 patients--points to remarkable trends and developments in the years between 1975 and 2002 [27]. The proportion of patients aged 50 or over significantly increased during the 27-year period to encompass more than one third (35.3%) of patients in 2002. Nearly 6.5% were 60 or older. During the same time, the proportion of patients aged 39 and under steadily declined. Data from other methadone centers in the US show comparable figures. According to the US Department of Health and Human Services [21], almost 10% of methadone patients were over the age of 50 at the end of the last decade, and more than 33% were between the ages of 40 and 49. While this data points to clear trends in aging methadone patients in the US, there is great variability across treatment centers. In a survey among ten methadone programs from nine states, estimates of the percentage of patients aged 55 or older ranged from 2% to 60% [18]. This raises the questions of why the discrepancy exists and whether these developments are restricted to the US or whether there are similar trends in other countries with relatively long traditions of methadone maintenance and rather high prevalence rates of opioid dependence. Slowly, these issues also attract attention in Europe, as demonstrated by the creation of collaborative projects like "SDDCare" to explore needs and establish treatment guidelines for senior drug users http://​www.​sddcare.​eu.

In Switzerland, the prescription of methadone for opioid dependence has been regulated by federal and state laws since 1975. Methadone maintenance treatment (MMT) is covered by health insurance and is provided by specialized clinics and office-based practitioners authorized to perform this treatment [28]. It is available for opioid-dependent individuals (according to ICD-10 criteria) aged 18 years or older who show opioid use on toxicology screening but are not able or willing to undergo abstinence-oriented treatment. Patients are generally free to choose their physician and treatment is covered by mandatory health insurance. Swiss health authorities substantially increased treatment programs in response to open drug scenes in several cities in the beginning of the 1990s [29]. Since then, there have been sufficient facilities for all patients willing to enter treatment. Thus, the threshold for entrance into MMT is low, with no further prerequisites other than opioid dependence. The name of every patient is reported to the local health authorities upon admission to MMT. Long-term abstinence is not an obligatory treatment goal and there are no restrictions regarding duration of treatment and dosing of methadone although currently a minimum dose of 60-80 mg/d is recommended [30]. Take-home dosages are often allowed for a maximum of one week. In March 2003, about 17,000 patients were on MMT throughout Switzerland [29]. From these, 958 were treated in Basel-City where the ratio of MMT patients to population has been roughly 0.5% since 1995. The MMT population of Basel has similar incidence trends, mean age and age of onset of heroin use as those of other cities in Switzerland [31]. We therefore assume the cohort to be representative for other Swiss cities.

This retrospective register-based cohort study sought to determine the age trends in the MMT population of Basel-City, Switzerland from April 1, 1995 to March 31, 2003, and to discuss some aspects of the potential consequences related to these developments in the future.

The analysis of methadone treatments in Basel-City indicates a clear trend in age development of the MMT population, as depicted in Figure 1. It shows a significant increase in older patients between 1996 and 2003. During that period, percentages of persons aged 50 and over rose tenfold from 0.4% in 1996 to 4.6% in 2003 (see Table 1). During the same period, the proportion of patients aged 29 and under dropped significantly from 52.8% in 1996 to 12.3% in 2003. This trend is reflected in the average age of patients, which stood at 30.3 years in 1996 and rose to an average of 38.0 years in 2003.

As shown in Table 1 the comparison of the patient samples of 1996 and 2003 reveals further trends as well as certain constants. The ratio of male to female patients remained virtually unchanged, whereas the proportion of employed patients working in jobs or receiving unemployment insurance payments dropped significantly from 48.9% to 24.1%. In the same period, the percentage of patients receiving a disability pension increased significantly, but the educational level also rose, overall, with more patients completing an apprenticeship or a higher education qualification. The 1-year retention rate in MMT improved greatly from 65.4% to 86.9% during this period. Similarly, data from 2003 shows an average methadone dose of 80.9 mg/d while the average methadone dose in 1996 was significantly lower, lying in the middle of the minimum effective dose range (60-80 mg). Of the 958 patients registered on March, 31, 2003, 458 persons had been on MMT continuously since 1995 or before. This amounts to almost half the 2003 sample (47.8%) while the overall number of MMT patients decreased by 19.8% over the observation period.

The data indicates that as this population ages, there is still a high rate of illicit substance use, with many patients using heroin and/or cocaine during the previous month (see Table 1). In 1996, 74.5% of the population reported using heroin during the preceding month while in 2003, 47.1% reported past-month heroin use. In contrast, the prevalence of self-reported cocaine use in the past month rose significantly from 36.5% in 1996 to 49.6% in 2003. Data from 1996 and 2003 show that patients aged 40 and older tended to report previous-month heroin use less often than younger patients (1996: 64.2 vs 75.4%, Chi2[1] = 4.08, p = 0.043; 2003: 42.2 vs 50.4%, Chi2[1] = 3.87, p = 0.049) while this was not the case for past-month cocaine use which did not differ according to age.

To our knowledge, this is the first register-based study addressing age trends among a MMT population in Europe. The results show a significant increase in both mean age and proportion aged 40 and older in MMT patients of Basel-City between 1996 and 2003. This trend is comparable to findings obtained in the US [18, 21, 27], although there have not been many of those and the present trends are less pronounced. The increase in age-coupled with a relatively stable prevalence of opioid dependence-corresponds well with the declining incidence of heroin use and the higher MMT retention rates in Switzerland [1, 32]. The 1-year retention rate of 86.9% in 2003 is certainly favorable [33‐35]. It reached a level of 65.4% as early as 1996, which compares well with national and international levels at that time [36‐39]. Taking into account other factors (e.g. improved clinical experiences, more adequate treatment of comorbid disorders) this increase could be due to a less restrictive MMT practice and the prescription of more effective methadone doses [33]. This change in treatment practice, may have contributed to the observed increase in patients aged 40 or older that requires particular attention. Furthermore, the observed age trends may be due to the effectiveness of MMT in decreasing mortality of drug users as compared to those not in treatment.

The findings also point to another relevant trend among MMT patients. As compared to 1996, there were considerably more patients receiving a disability pension or social welfare benefits in 2003, which also may be a consequence of this population's aging and its problems related to prolonged substance use and associated lifestyle, such as comorbidity, malnutrition, loss of work, unsanitary living conditions, violence, and trauma [40‐42].

Among the MMT population of Basel-City, past-month heroin use decreased significantly through time, from 74.5% to 47.1%. This could be the result of higher methadone doses and longer stays in treatment [13, 28, 33]. However, past-month cocaine use in this population increased from 36.5% to 49.6%. This finding is comparable to that of a study of clients of Swiss needle-sharing facilities from 1993-2006 [43]. Among other reasons, this shift from heroin to cocaine use may be the result of the decreasing price of cocaine [44] or the declining purity of street heroin which may lose attractiveness in the light of agonist properties of methadone received in treatment. New patterns of consumption have accompanied the shift, with heroin, cocaine and sometimes rapid-onset benzodiazepines used together [43]. The sustained increase in cocaine use among MMT patients contrasts with the relatively constant prevalence in the general population [45] and underlines the increased vulnerability for multiple drug use in this group.

Despite these limitations, two conclusions can be drawn from the present findings. First, MMT populations are getting older, not only in the US but also in Switzerland and most likely in many other European countries. Second, MMT practice has changed in the last decades, which is corroborated by other studies [71, 72] and is most likely owed to research. However, as positive as these trends are, they will pose challenges for MMT providers and the entire health care system in the near term. We would welcome increased efforts from researchers and practitioners to deal with this issue. It is time for us to develop resources and to use them to meet the special needs of this patient population, and to train staff accordingly. Increased knowledge about these persons' needs, and the special issues involved in their care, will help decrease prejudice against them, improve the quality of care, and, indeed their quality of life.