PREVALENCE OF POLYPHARMACY

Since the 1970s, studies on drug use have reported the prevalence of polypharmacy for population-based samples and community-dwelling elderly persons (Table 1, Table 2), whereas the earliest reports for elderly hospital patients and nursing home residents are from the 1980s (Table 3). Studies reporting polypharmacy show a wide range in prevalence estimates. Direct comparisons of prevalences between studies are difficult due to inconsistent definitions of drug use: some studies take into account only prescription drugs, while others include over-the-counter drugs, vitamins, mineral supplements and herbals.

The importance of the time period under which data on drug use is collected was illustrated in a study that reported separately the mean number of prescription drugs used during the preceding two days (1.8), two weeks (2.2) and three months (2.6) (136).

Polypharmacy in population-based samples and community-dwelling elderly persons

According to a Swedish study, every fourth (26%) person aged 70 years was using four or more prescription drugs concomitantly in the early 1970s (13). The corresponding prevalence was 34% among Finnish retirement home residents (149). Of community-dwelling elderly Americans, 18% were using five or more prescription drugs in the late 1970s. When taking into account both prescription and over-the-counter drugs, the prevalence of the use of five or more drugs was 13% for a population-based sample of elderly Finns aged 70–79 years (51). A somewhat higher proportion (23%) was found in a study of community-dwelling cohort of those aged 65 years and older (135).

In the 1980s, US studies reported prevalences between 10% and 18% for the use of five or more prescription drugs among persons aged 65 years and older (33,92,97,150). Using the same definition of polypharmacy, a similar (10%) prevalence was also observed in England (31). Of Finnish elderly persons, every fifth (22%) was reported to use five or more prescription/over-the-counter drug at the end of 1980s (51). Seven or more prescription drugs were used by one in ten (8%) of those aged 70 years and older (129).

Epidemiological research on drug use of elderly persons increased remarkably during the 1990s (Table 1, Table 2). Over this decade, the lowest prevalences for the use of five or more prescription drugs among persons aged 65 years and older were reported in the Netherlands (2–4%) (66) and the UK (10%) (35). The corresponding prevalence was 39% for Swedish community-dwelling elderly persons of the same age (34). For Finnish elderly persons aged 65 years and older, the prevalence of the use of six or more prescription drugs showed an increase from 19% to 25% during the 1990s (80). When also taking into account over-the-counter drugs, the prevalence of the use of five or more drugs varied between 15% and 40% among persons aged 75 years and older living in European countries (14,52,53,55,59).

US studies on persons aged 65 years and older have reported fairly high prevalences. Among women, 59% were reported to use five or more prescription/over-the-counter drugs (63). Furthermore, when including vitamins, mineral supplements and herbals as well, a prevalence of 63% was found in a population-based US study (67)

In the 2000s the prevalences for polypharmacy in population-based samples and community-dwelling elderly persons were generally higher than in the previous decade (Table 1, Table 2). Large Swedish register-based studies reported that over half (52–57%) of those aged 75 years and older were using five or more prescription drugs (42,44).

For a population-based sample of Swedish elderly, the prevalence was 42% when counting both prescription and over-the-counter drugs. The corresponding prevalence among those aged 70 years and older was 54% in a German study (61). High prevalences (42–65%) have also been observed in other studies of prescription drug use among populations aged 65 years and older (38,43,47,48). The lowest prevalences concerning prescription drug use were reported in Asian countries: 12% for the use of five or more drugs in Taiwan (143) and 36% for the use of six or more drugs in Japan (142). Using five or more drugs as a definition of polypharmacy, an US study reported a prevalence of 58% when including also vitamins, mineral supplements and herbals besides prescription and over-the-counter drugs (68). A recent study of Polish centenarians showed that one in three (33%) used five or more drugs prescription/over-the-counter drugs (151). In a European study the prevalence of polypharmacy, defined as the use of

six of more prescription/over-the-counter drugs, was estimated among home care elderly persons from eight different countries in the beginning of the 2000s (141). This study revealed that the highest prevalence of polypharmacy was seen in Finland (73%) and the Czech Republic (68%), whereas the lowest prevalences were found in Italy (36%), the Netherlands (35%) and Norway (34%) (Figure 1).

Figure 1. Prevalence of polypharmacy (≥6 drugs) and excessive polypharmacy (≥9 drugs) for home care patients aged 65 years and older in European countries during 2001–2002 (Rx and OTC drugs included) (152)

% 73 68 64 50 48 363534

41 39 32 1820 7

13 11 0

10

20

30

40

50

60

70

80 Finland n=187Czech Republic n=428

Iceland n=405Denmark n=400United Kingdom n=289 Italy n=412The Netherlands n=198 Norway n=388

≥6 drugs ≥9 drugs

Excessive polypharmacy in population-based samples and community-dwelling elderly persons

The earliest estimates on excessive polypharmacy for population-based samples and community-dwelling elderly persons are from the 1990s (Table 1, Table 2). In a Swedish study of community-dwelling persons aged 75 years and older, 13% were found to use ten or more prescription drugs in the mid-1990s (34). Using the same cut-off point for excessive polypharmacy, a prevalence of 12% was found for persons aged 65 years and older in a US study that counted also over-the-counter drugs, vitamins, mineral supplements and herbals besides prescription drugs (67). Among US women, a similar prevalence (12%) was observed for the use of ten or more prescription/over-the-counter drugs (63). An Italian study conducted in the early 1990s reported that 11% of those aged 75 years and older were using seven or more drugs concomitantly (52).

Studies conducted during the 2000s have reported prevalences between 11% and 20% for excessive polypharmacy, defined as the use of ten or more drugs (48,68,69). All of these studies included populations aged 65 years and older (Table 1, Table 2). Similar prevalences (10–18%) were found for the use of ten/eleven or more prescription drugs in Swedish register-based studies of populations aged 75 years and older (42,44).

Studies examining drug use patterns in home care patients have reported remarkably higher prevalences of excessive polypharmacy than those using population-based samples or community-dwelling elderly persons (Table 1, Table 2). A US study showed a prevalence of 39% for the use of nine or more prescription drugs (90), while the prevalence was 22% in a large European study that also included over-the-counter drugs (141). Country-based prevalences showed that excessive polypharmacy was most common among Finnish (41%) and Czech (39%) elderly home care patients (Figure 1). The lowest proportions were found in Norway (11%) and Italy (7%).

Polypharmacy in elderly hospital patients and nursing home residents

Research on polypharmacy in institutionalized elderly persons was scarce before the 1990s (Table 3), with only a few articles reporting on the prevalence of polypharmacy among the US population aged 65 years and older in the 1980s. According to these studies, two-fifths

(43%) were using four or more (130) and one-third (33%) five or more (32) prescription drugs in the late 1980s.

In an Australian study comparing cross-sectional cohorts of nursing home residents the proportion of those using five or more prescription drugs increased from 42% to 64% during the 1990s (40). When taking into account prescription and over-the-counter drugs, high prevalences were also observed in other countries: 83% of Canadian (36) and 66–79% of US (39,54,60,132,153) elderly persons aged 65 years and older used five or more drugs concomitantly.

When comparing the prevalences of polypharmacy reported during the 2000s, wide variation can be observed between countries. In Turkey only 17% of persons aged 60 years and older used five or more prescription/over-the-counter drugs (57). Japan was the other country where a low prevalence was observed, as 27% of the oldest old persons (aged 85 years and older) were using six or more prescription drugs.

Studies conducted in European countries have reported 60–80%

prevalences for polypharmacy defined as the use of four/five or more prescription drugs (45,121,147). In the early 2000s, the corresponding prevalence was 71% in Australian nursing homes (40). The highest prevalence for the use of five or more prescription drugs (90–91%) was among Indian hospital patients aged 60 years and older (49) and Australian demented nursing home residents aged 65 years and older (112).

Excessive polypharmacy in institutionalized elderly persons

US studies conducted in the 1990s revealed a prevalence of 21–38% for the use of nine/ten or more drugs among hospital patients aged 65 years and older (9,39,54,60,132,153). In Canada, 46% of nursing home residents of the same age used nine/ten/eleven or more prescription drugs (36). In Italy, one in four (23%) elderly patients used seven or more drugs at discharge from hospital (146).

In the 2000s, two-fifths (39%) of US nursing home residents aged 65 years and older were using nine or more prescription drugs (108). Of Irish hospital patients aged 75 years and older, quite a low proportion (9%) was using ten or more prescription drugs (70). In Indian hospitals, the corresponding proportion was 45% for patients aged 60 years and older (49). An Austrian study of hospital patients aged 75

years and older found a prevalence of 58% for the use of seven or more prescription drugs (107).

4 Factors Associated with