Cannabis – Chronic Pain in German General Practice

ABSTRACT

Introduction. This study evaluates the prevalence of chronic pain, intensity of pain, activity limitation, and pain-related diagnoses in German general practices.

Methods. In 40 general practices, up to 50 consecutive patients presenting to general practitioners (GP) for routine medical consultation were questioned, and those reporting pain that lasted for more than 3 months received a questionnaire referring to intensity of pain and activity limitations. GPs received a questionnaire asking about the duration of treatment and diagnoses.

Results. Three hundred forty-six out of 1,860 questioned patients suffered from pain that lasted for more than 3 months (a point prevalence of 18.4% [95% confidence interval 16.7–20.3]). The average degree of pain equaled 5 out of 10 points on a numerical grading scale (NRS); the average degree of activity limitation was 4.8 out of 10. In most cases, the pain was related to musculoskeletal degenerative diseases.

Conclusion. Chronic pain patients constitute a considerable share of workload in general practice.

Introduction

Public awareness of chronic pain and its socioeconomic impact has been increasing worldwide [1]. Prevalence in the general population ranges between 15% and 45%, depending on population segment and research method [2–4]. Also, in Germany, the number of people suffering from chronic pain appears to have increased. It is estimated that 5 out of the 85 million inhabitants experience pain for periods of 6 months and more, leading to considerable limitations on activities in daily life [5]. Up to now there are six population-based studies on the prevalence of chronic pain in Germany. A postal survey found a prevalence of 39% [6]; a telephone survey showed a rate of 17% [7]. A prevalence of 31% was calculated for children and adolescents [8], and 13% for women [9]. Other surveys focused on defined types of pain: chronic back pain (male: 16%; female: 22%) [10] and chronic headaches (3–21.5%) [11]. Methodological considerations limit the application of these data to the population in general: retrospective data are biased by present pain experiences, and statements are not confirmed by diagnoses [12]. Studies from general practice may broaden the perspective, providing more precise data for duration and intensity of pain, for characteristics of chronic pain patients, and for activity limitation, related diagnoses, and psychiatric comorbidity. But also, the generalization of such clinical samples is limited. Selection bias due to office opening times or health care-seeking behavior is probable and may influence prevalence estimates.

Studies carried out in primary care settings in Finland [13], Sweden [14], Denmark [15], and Italy [16] showed point prevalence rates of 15–20%. Two small, nonrepresentative studies (one practice, respectively) were carried out in German general practice and demonstrated two different chronic pain ratios: 35% [17] and 20% [18]. Different from most other countries, Germany has an unusual high rate of general practitioner (GP) visits per patient (around 10 visits per year), and an unusual high proportion of inhabitants see a GP per year: 85% [19]. The study presented here presumes to be more representative than the other German studies cited by sampling a much larger study population from a wider variety of practice settings. Its objective is to determine the prevalence of patients suffering from pain in German general practice, intensity of pain, activity limitation, types of pain, and pain-related diagnoses.

Methods

This cross-sectional survey was conducted in 40 general practices in five large cities and their rural surrounding areas in Baden-Württemberg, Hessen, and Nordrhein-Westfalen from May 1 until August 31, 2005. Some practices were recruited from contact lists provided by three university departments in the above-mentioned regions. The other practices were recruited from GP quality circles. These GP quality circles took place in the same university departments where GPs are trained in student teaching and pharmacotherapy. They were not randomly selected but stratified with regard to the sex of the participating GP and to the rural/semi-urban vs urban sites, respectively. Some of the practices were group practices (15 of 40) with two or more GPs, the others were single practices. This rate of 37% group practices is slightly higher than the German average.

Up to 50 consecutive patients (over 18 years of age) who consulted the practice (for normal consultations and only with direct contact with the GP) were asked face-to-face by practice nurses or one of the researchers (MB) to participate in the study. Recruitment occurred on one random working day to avoid selection bias. When a patient agreed, he/she was asked the following filter question: “Have you experienced pain, or did you receive pain treatment for more than 3 months?” By using a single filter question instead of a questionnaire, we expected to increase the rate of patient participation. This question has not been previously validated, and therefore, we do not know its operating characteristics (sensitivity and specifity). Patients, who responded “Yes” to the filter question, were asked to complete a validated questionnaire (see below) referring to pain intensity, pain persistence, and limitations on activities in daily life. Although the filter question per se has not been validated, it is similar semantically to the question in the validated questionnaire applied. For further control, GPs completed a questionnaire concerning pain duration, pain-related diagnoses, and other patient data.

These study procedures were not approved by an Institutional Review Board.

Questionnaires

Patients reporting persistent pain or pain treatment for more than 3 months were given a questionnaire assessing intensity of pain and limitations on activities in daily life using the validated German translation of “Chronic Pain Grade Scale”[20,21]. Localization of pain was indicated in a list, as part of the questionnaire.

For each consenting patient, his/her GP received a non-validated questionnaire on duration, pain-related and psychiatric diagnoses, and demographic data. Because there are two parallel definitions for chronic pain duration (3 or 6 months), both were studied.

Statistics

The sample size was calculated for an estimated point prevalence of 20% using the prevalence figures of previous studies (for pain lasting longer than 3 months) and accepting a standard deviation of 2% resulting in 1,536 cases. The analysis was mainly descriptive, reporting absolute and relative frequencies. Confidence intervals (CI) (95%) were indicated only for the point prevalence. Chi-squared test and Cochrans’s trend test [22], respectively, were used for calculating differences in pain intensity and pain-related limitation of activities in daily life.

Results

The filter question (“Have you experienced pain, or did you receive pain treatment for more than 3 months?”) was asked to a total of 1,860 patients (minimum 27, maximum 5; in median, 47 patients per practice; the three practices with complementary medicine recruited less patients).

Only 26 patients (1.4%) refused to answer the filter question. No pain of longer duration was reported by 1,407 patients. Pain of longer duration (more than 3 months) was reported by 427 patients. Out of these, 81 patients (18.9%) refused to complete the questionnaire. Overall, 346 patients suffering from pain of more than 3 months duration could be analyzed more in depth (Figure 1).

Patient Characteristics

Three-quarters of chronic pain patients were over 50 years of age. Among these, the largest group was 70–80 years of age; 13% were over 80 years (see Table 1). In German general population, the male/female ratio is 49:51, whereas in this sample, twice as many women as men consulted their GP for chronic pain treatment. A rate of 22% of pain patients were smokers, slightly less than in the German average population. Considering the advanced age of pain patients, in comparison with the corresponding age group, the smoking rate is normal [23]. The 51:49 ratio of patients’ place of residence (rural/semi-urban vs urban) corresponds to the actual distribution in Germany (51.2 vs 48.8%) [24]. In contrast to the German general population, this sample of chronic pain patients has higher numbers of people in manual professions (31 vs 14%) and full-time housewives (9.8 vs 5%), and lower numbers of people in non-manual (15.3 vs 32%) and academic professions (8.7 vs 18%) (Table 1).

Prevalence

Of the 1,834 respondents to the filter question, 427 reported pain lasting longer than 3 months: a prevalence of 23.3% (CI 21.4–25.2%) for the 3-month duration.

Responses from the completed validated questionnaires (N = 1,834) showed a prevalence of 18.4% (CI 16.7–20.3%) for pain over a 3-month period, and a prevalence of 17.0% (CI 15.3–18.8%) for pain of 6 months duration.

The prevalence rates derived from the questionnaires completed by the GP were somewhat lower: 16.4% (CI 14.7–18.1%) for 3 months duration and 14.1% (CI 12.6–15.8%) for 6 months (Table 2).

Site of Pain

Two-thirds of the participants reported multiple sites of pain. This includes patients reporting pain in the lower back (50%), joints (44%), headache (16%), and abdomen (9%). Pain in unspecified sites was reported by 10% of the patients (Figure 2).

Intensity of Pain and Limitations of Activity in Daily Life

With regard to the median of experienced pain intensity, most patients report moderate pain (44%), followed by mild pain (28.0%) and severe pain (14.4%). Very severe or very mild pain was rarely mentioned. However, with regard to the maximum level of pain experienced during the last 3 months, 42.1% of the patients reported that they experienced severe pain, and 29.1% reported that they experienced very severe pain at least once. Pain-related limitation of activity and work is rated almost equally (20–28%) as mild, moderate, or severe. As compared with limitations of activity, limitations on recreational activities were judged more often as most severe (12.1 vs 7.3%; P = 0.059), and less often as light (18.1 vs 27.6%, P = 0.039).

No difference was found (P = 0.80) between the age groups before retirement (in Germany, on average, before age 62 years) and after retirement (after age 62 years).

Many patients (58%) reported not being able to pursue their usual activities (work, household, and school) for an unspecified period of time. There were a considerable number of patients (11.9%) who reported periods of disability of more than 6 weeks ( Tables 3 and 4).

Diagnosis

The study requested information on the GPs’ medical diagnoses (of participating patients). Several diagnoses were made for about a third of the patients. The majority of patients had degenerative musculoskeletal diseases (66.8%), followed by functional disorders (with symptoms for which no pathophysiological causes can be identified, i.e., medically unexplained), especially pain syndromes relating to the head and lower back (14.5%). About one-tenth of the pain patients suffered from inflammatory diseases (mostly chronic polyarthritis or other rheumatic diseases), metabolic diseases (obesity and diabetic polyneuropathy), or idiopathic diseases (mostly fibromyalgia), respectively. Vascular diseases (coronary heart disease and peripheral arterial disease), cancer, and post-traumatic states were less frequent. Psychiatric co-diagnoses were given for about a third of the patients. These were mainly depressive disorders (22.8%). Rarely given diagnoses were somatoform disorder (2.9%), neurotic diseases (2.6%), psychotic diseases (0.6%), phobia (0.6%), or addiction (2.6%) (Figure 3).

Discussion

About a fifth of patients in general practices in Germany suffer from chronic pain (point prevalence of 23.3% assessed by a filter question; point prevalence of 18.4% assessed by a validated pain questionnaire). These results do not differ significantly from other European practice studies [14–16].

Our practice study found the highest prevalence of chronic pain in the 70–79-year-old age group. In contrast, German population-based studies [6,12] had higher prevalence rates in the 45–64-year-old age group.

The high rate of female sufferers (2:1) confirms European practice studies’ data [15,29], but are in contrast to population-based studies with higher percentages of male patients [7,12]. An explanation can be that women are more likely to visit a doctor for pain-related treatment.

Although average pain intensity is of “medium severity,” a relevant portion of chronic pain patients (19.3%) suffered from severe pain. Hence, in German general practice, there are a relevant number of pain patients with a high level of suffering.

A large proportion of patients (58%) reported not being able to pursue their usual activities for certain periods. This rate is higher than the rate found in population-based studies (9–40% [21]) or other practice studies (19% [17]). It is worth noting the relevant proportion of patients being disabled for usual activities for longer than 6 weeks (11.9%). As other practice studies (e.g., 13) also found substantial sick leave times, an important economic burden for employer and health insurances can be assumed.

In this sample, chronic pain is predominantly attributed to degenerative diseases, probably due to the advanced median age. Consequently, functional pain syndromes (with no identified pathophysiological causes) regarding the back and the head are less frequent than in population-based studies with younger samples [12]. Cancer as the cause for pain syndromes is infrequent (5.2%). Its prevalence in primary care may be low because of shorter duration of disease, longer inpatient stay, and often specialized care. The rare diagnosis of vascular diseases as a cause for pain (5.8%) corresponds to the findings of other European practice studies [13,14]. The considerable rate of depressive syndromes as co-diagnosis (22.8%) corresponds to the results of other studies in primary care settings [30–32]. Population-based studies in Europe [7,33,34] and North America [21,35,36] showed slightly lower rates (16–20%). It is reasonable that people seeking care are more likely to have major health problems.

Limitations

The practice sample is only representative for the two stratified features: sex of the participating GP and local distribution (urban vs semi-urban/rural). The number of 7 academic teaching practices among the 40 recruited is not representative of German general practice. The survey only covered the occurrence of patients suffering from pain, but the number of consultations for chronic pain was not taken into account. There are no data about sensitivity and specifity of the used unvalidated filter question, so over- or underestimation of the prevalence is possible. Because of the relevant number of patients who reported chronic pain to the filter question but not consented to answer the validated questionnaire (18.9%), an underestimation of prevalence is possible. The used pain questionnaire “Chronic Pain Grade Scale” had been validated only among an unselected population with normal distribution of age [21]. Given the advanced age of the study participants and their high rate of physical impairment, it is possible that the rates of pain-related limitation in activities of daily living, etc., were overestimated. The questionnaire given to GPs was not validated. Data for pain-related diagnosis and psychiatric diagnosis were not based on standardized clinical assessment but were dependent on doctors’ International Classification of Diseases (ICD) coding, which usually contains high variability.

Conclusions

Chronic pain prevalence in German general practice is slightly lower than levels assessed in German general population-based studies. Nevertheless, there are a relevant number of pain patients with a high level of suffering, constituting a considerable share of workload. Pain treatment as well as diagnosis and treatment of degenerative and depressive diseases require further attention. There is a need for studies that analyze care in general practice (treatment, referrals, and patient’s expectation).

Conflict of Interests

The author(s) declare that they have no conflicting interests. There was no grant or financial support for this study.

Acknowledgments

We wish to thank all participating patients and GPs who participated in the study.