Epidemiology of periodontal diseases in Europe

Epidemiology is primarily concerned with the prevalence of diseases in populations. However, the prevalence of periodontal diseases is in most populations very high and pure descriptions of the prevalence, including mild and reversible forms like gingivitis (prevalence ≈ 100 %), would be of little or no value. Moreover, there are indications that gingivitis should not be regarded as belonging to the same entity of diseases as destructive forms of periodontitis (^{Page, 1986} ; ^{Prayitno et al., 1993}). Periodontal epidemiology will, in addition to prevalence, usually also be concerned with various expressions of disease severity.

An inherent problem in periodontal epidemiology is the lack of clear-cut criteria of disease and health, which again is due to great difficulties concerning diagnosing periodontitis as a disease. Current methods are at best able to assess the disease state as a condition caused by a distant or recent historic process. The problem is approached by describing various characteristics which either reflects the degree of inflammation (bleeding on probing) or accumulated disease experience (clinical loss of attachment, radiographic bone loss) or both (pocket depths). The picture is even more complicated if the extent of the disease (number of quadrants, sextants, teeth or sites involved) in each individual also is considered. These and other methodological problems faced in periodontal epidemiology were recently reviewed by ^{Papapanou (1994)}.

Based on the above mentioned options for describing the periodontal status of individuals, several indices to measure both extent and severity has been used in epidemiological research in the field. In addition to the fact that different studies have used different examiners, which will introduce errors when studies are compared, this makes it extremely difficult to compare results from various studies in order to describe the disease status in a large region as Europe. Furthermore, representative national studies are almost non-existing. Most studies have been performed on representative samples of defined subpopulations or in various convenience samples with unknown representativity.

For the purpose of the present review paper, I have decided to include only studies where the samples are relatively large and where representativity in some way may be assumed. Studies published before 1982 are not included, since changes in periodontal disease over time have been reported from several European locations (^{Baerum et al., 1985} ; ^{Hansen et al., 1990} ; ^{Hugosson et al., 1995}).

Also, it seems logical in this context not to describe extent of the disease within the dentition, but include subjects as either displaying indicators of disease at moderate or severe state, only. Gingivitis which is a reversible condition, and which is regarded rather rarely to develop into periodontitis (^{Page, 1986} ; ^{Attström and van der Velden, 1994}) has been disregarded in this review. Thus, only subjects with irreversibly accumulated disease experience will be discussed. By simplifying the results and collapsing the results as suggested it is believed that a better platform for comparisons on a population level is established.

Since studies employ various ways of describing the disease indicators, I have chosen to regard subjects with indications of moderate loss of support in one or more sites of the mouth (pocket depths 3-5 mm, clinical loss of attachment or radiographic loss of bone 1-3 mm) as having moderate periodontal disease and those with one or more sites displaying worse figures as having severe periodontitis. Such dichotomization of persons with periodontitis has been argued for by ^{Burt (1990)} and ^{Pilot and Miyazaki (1991)} because this may separate those individuals who run a risk of loosing a substantial number of teeth due to the disease from those who probably will not. Since the indicators chosen reflect the accumulated disease experience in a population, there is always a strong association between periodontitis and age in epidemiological studies. In the present review the author has tried to separate between young individuals (under the age of 30-35), middle aged (from 30-35 to 50-55) and old age individuals as being more than 50-55 years of age. The results of the cited studies have been modified to fit the above description.

Descriptive data

The WHO Global Oral Data Bank comprises data for periodontal conditions for more than 78 000 European subjects between 15 and 44 years of age from 28 different countries based on the CPITN (^{Ainamo et al., 1982}). This index has been criticized for not describing the periodontal status accurately (^{Hansen et al., 1990} ; ^{Gjermo, 1991} ; ^{Papapanou, 1994} ; ^{Attström and van der Velden, 1994}) but will suffice for the present review with the limited interpretation of the data and probably contribute to give rough estimates of the prevalence of affected individuals. Also, most of the surveys performed in Europe in the last 2 decades are based on this index and it would not be feasible to disregard them.

It is evident from the data of the WHO Global Oral Data Bank, comprising information from more than 78 000 European citizens, that very few young individuals suffer from severe disease and very few in the older ages are without disease experience. In the age group 15-19 years of age only 0.7 % displayed signs of severe disease while 88.9 % were without evidence of loss of supporting tissue. The respective figures for the age group 35-44 were 18.7 % and 47.9 %. Moderate disease was expressed in more than one site in 10.6 % and 35.7 % in the 2 age groups, respectively. Among dentate subjects in the age group 45-54 years 36.0 % was affected by serious disease, whereas 31.9 % showed indicators of moderate disease, leaving approximately 32 % without disease experience (^{World Health Organization, 1994}).

There seem to be large variations in periodontal conditions among countries and regions in Europe. Several studies from the Scandinavian countries indicate a relatively low prevalence of severe disease in these populations. ^{Baerum et al. (1985)} reported from a central Norwegian region that approximately 5 % of the population (age 13-54) had one or more pockets > 6 mm, ranging from 0 % under the age of 30 to 13 % at more than 45 years of age. In Sweden reports indicate a prevalence of persons with severe disease as low as 2 % through all age groups, and 0 % under the age of 40 (^{Hugosson et al., 1995} ; ^{Hugosson and Jordan, 1982}). A large representative study from Denmark also indicates that 2 % only, of the adult population (16-64 years of age) suffer from more severe forms of periodontitis, ranging from almost 0 % under the age of 30 to approximately 5 % in the age over 50 (^{Kirkegaard et al., 1986}). Moderate disease indicators were present in 19 %, ranging from 9.5 % to 31 % by age. Several other studies from Scandinavia confirm the rare prevalence of periodontitis under the age of 30 and low proportions of the populations with severe disease at later ages (^{Aass et al., 1988}, ^{Källestål et al. 1990}, ^{Albandar, 1990}). A representative study from Finland, covering the adult population over 30 years of age showed a somewhat higher prevalence of severe disease (25,6 %) (^{Markkanen et al. 1983}). Only 23.2 % were reported to be without periodontal disease experience. These findings were in part corroborated by ^{Ainamo et al. (1986)} in a study of dentate subjects from Northern Finland.

Also from Switzerland very low rates of severe disease have been reported. In a representative study from Berne, ^{Schürch et al. (1988)} found a prevalence of deep pockets and attachment loss in approximately 2-3 % of the population, while approximately 25 % were affected by moderate disease across all ages.

Other European countries seem to have a higher prevalence of both moderate and severe disease. From a representative sample from a region in France can be deducted that 10 % displayed severe signs of disease, 32 % moderate, while 58 % did not show any site with loss of attachment or pocketing > 3 mm (^{Miller et al. 1987}). ^{Strohmenger et al. (1991)} found in a large Italian population comprising approximately 55 000 subjects that 10 % had deep pockets and that 30 % had moderate pockets. Very similar results have been reported from Croatia (^{Plancak and Aurer-Kozelj, 1992}) and Portugal (^{Freitas et al. 1983}).

Data indicate that the most severe periodontal disease status in Europe is present in Eastern Europe and in Germany (^{Neumann et al., 1989} ; ^{Skaleric and Kovac-Kavcic, 1989} ; ^{Mengel et al., 1993} ; ^{Hohlfeld and Bernimoulin, 1993} ; ^{World Health Organization, 1994} ; ^{Micheelis and Bauch, 1996}). However, there are great variations in this picture inside Germany, mainly indicating a better situation in the former West Germany (BRD) (^{Gaengler et al., 1988} ; ^{Pilot and Miyazaki, 1991} ; ^{World Health Organization, 1994} ; ^{Micheelis and Bauch, 1996}).

^{Table I} is constructed based on those studies that could give information of the variables included in the table. Since data on prevalence of moderate disease due to uncertainties of the differentiation between health and early signs of disease are difficult to interpret, signs of severe disease among the middle aged populations were chosen in an attempt to group various countries according to the periodontal condition of their populations (^{table II}).

Developmental trends

Repeated epidemiological surveys from the same populations, cohort studies or longitudinal studies following the development of the disease status over time are scarce. However, there are some studies which indicate an improvement of the periodontal status over time, in particular it seems that the proportion of populations displaying the worst condition is reduced over time. ^{Hugosson et al. (1995)} showed in a series of repeated cross-sectional studies from the same population a strong reduction in gingivitis between 1973 and 1983. This trend seemed to flatten out during the following decade. However, the periodontal condition of this Swedish population improved during the whole 20 year period and revealed that 40 year olds in 1993 had periodontal conditions similar to the 20 year olds in 1973. This would indicate that no deterioration of the periodontal condition took place over 20 years in the birth cohort from 1953.

Similar, but somewhat less impressing results, were reported from a Norwegian survey conducted in 1973 and repeated in 1983 (^{Baerum et al., 1985}). ^{Hansen et al. (1990)} conducted surveys of the periodontal treatment needs among 35 year old Oslo citizens in 1973 and 1984. They could demonstrate a reduction of approximately 30 % of persons with the worst condition. In a longitudinal study over 15 years the periodontal condition was monitored from age 35-50 by the same group in a representative sample from Oslo, Norway (^{Hansen et al., 1995}). It was shown that at the age of 35, 32 % had one or more deep pockets, while at the age of 50, this was reduced to 30 %. The average loss of teeth per subject in this population was 0.25 only, for the whole period, and could not account for the improvement. Similarly, a longitudinal study of British workers showed a marked improvement of the periodontal condition over 14 years (^{Sheiham et al., 1986}), although this particular population also lost a substantial number of teeth during the period of observation (mean pr. person, 4.6) and 16 % of the population became edentulous. These latter observations may explain part of the observed reduction in severe periodontitis, assuming that the teeth lost were those with the most severe periodontal condition at the start.

In another population from Oslo the periodontal status was monitored over 6 years by means of radiographs (^{Albandar, 1990}). More than 90 % of the more than 5 500 sites in the 142 subjects did not change over 6 years, indicating a very slow progression of periodontitis in the studied group. Similar results, using clinical indicators, have been described among a group of Norwegian academicians (^{Löe et al., 1992}).

There are indications that radiographic bone loss may affect increasing proportions of the young populations throughout their adolescence (^{Clerehugh et al., 1990}, ^{Aass et al., 1994}). It has been postulated that early bone loss may serve as an indicator for risk subjects (^{Gjermo, 1984}), but this has not yet been established.

Unfortunately, no studies of longitudinal character are available from European countries with an expected higher prevalence of severe periodontal conditions (^{table II}).

Analytical studies

As a consequence of the epidemiological methods of assessing periodontitis (accumulated disease experience), a strong correlation with age is always present. However, the presence of indicators of severe disease in young age must be rgarded as a more serious expression of the disease than the presence of the same indicators at older age.

Although gender is generally believed to be associated with severe periodontal disease (^{Johnson, 1994}), most European studies cannot confirm this relationship (^{Baerum et al., 1985} ; ^{Schürch et al., 1988} ; ^{Källestål and Matsson, 1990} ; ^{Hansen et al., 1990} ; ^{Strohmenger et al., 1991}). However, a comprehensive Danish study revealed that a significantly higher proportion of men than women was affected by severe periodontal disease (^{Kirkegaard et al., 1986}).

Variables like place of living (urban/rural) and education has been found not to be associated with disease status in a series of studies (^{Baerum et al., 1985} ; ^{Schürch et al., 1988} ; ^{Hansen et al., 1990} ; ^{Källestål and Matsson, 1990}), while a strong association between disease experience and smoking habits seems to emerge from recent studies (^{Bergström, 1989} ; ^{Bergström et al., 1991} ; ^{Johnson, 1994}). Other studies indicate an association with oral hygiene and dental visit habits (^{Hansen et al., 1990} ; ^{Källestål and Matsson, 1990} ; ^{Mengel et al., 1993}).

Concerning progression of periodontitis, longitudinal studies reveal associations with presence of subgingival calculus (^{Clerehugh et al., 1990}) and other oral hygiene indicators (^{Sheiham et al., 1986}).

Recently emotional stress has been focused as a possible risk factor for periodontal diseases (^{Breivik et al., 1996}). A British case-control study comprising 100 dental patients reported a significant effect of negative life events upon the periodontal status (^{Croucher et al., 1997}). A negative correlation between positive life events and severity of periodontitis was also observed, but this association did not come out with significance on the 95 % level. These findings would support the notion that emotional stress may affect the immune response to a degree which could change the course of a chronic infection like periodontitis.

Concluding remarks

Epidemiological studies of periodontal diseases in Europe through the last 2 decades confirm the now generally accepted pattern : Very few subjects under the age of 30 show signs of severe disease, and even in older age the prevalence of subjects with severe disease in most studies are restricted to 15-20 %. Also, it seems that those affected rarely display more than a few teeth affected. Thus, periodontal diseases is not expected to cause a large number of edentulous persons in Europe (^{Klock and Haugejorden, 1991} ; ^{Papapanou, 1994} ; ^{Baelum et al., 1996}). However, it seems possible to discern a difference between regions in Europe concerning the prevalence of indicators of severe periodontitis among middle aged individuals. Thus, Eastern European countries seem to have more people with severe disease.

In Western Europe, where the periodontal conditions seem to be better than in the east, there is a trend towards continued improvement of the existing conditions. Studies which may reveal such trends are not available from the eastern part of Europe.

Factors associated with the periodontal condition, in addition to age, seem to be smoking habits, oral hygiene and regularity of dental visits.

The data and interpretations presented in this review have been based on many studies performed with various methods by many investigators and with different intentions. Thus, all estimates are very uncertain, but since only course indicators of the disease have been used, the overall picture may be regarded as credible. Detailed comparisons based on the compiled material is not warranted.

BIBLIOGRAPHY

• AASS AM, ALBANDAR J, AASENDEN R, TOLLEFSEN T, GJERMO P. Variation in prevalence of radiographic alveolar bone loss in subgroups of 14-year-old schoolchildren in Oslo. J Clin Periodontol 1988;15:130-133.
• AASS AM, TOLLEFSEN T, GJERMO P. A cohort study of radiographic alveolar bone loss during adolescence. J Clin Periodontol 1994;21:133-138.
• AINAMO J, BARMES DE, BEAGRIE G, CUTRESS T, MARTIN J, SARDO-INFIRRI J. Development of the World Health Organization (WHO) Community Periodontal Index of Treatment Needs (CPITN). Int Dent J 1982;32:281-291.
• AINAMO J, TERVONEN T, AINAMO A. CPITN-assessment of periodontal treatment needs among adults in Ostrobothnia, Finland. Comm Dent Health 1986;3:153-161.
• ALBANDAR JM. A 6-year study on the pattern of periodontal disease progression. J Clin Periodontol 1990;17:467-471.
• ATTSTRÖM R, VAN DER VELDEN U. Consensus report of Session I. In : Proceedings of the 1st European Workshop on Periodontology. Lang NP, Karring T, eds. London : Quintessence Publishing Co Ltd, 1994.
• BAELUM V, CHEN X, MANJI F, LUAN WM, FEJERSKOV O. Profiles of destructive periodontal disease in different populations. J Periodont Res 1996;31:17-26.
• BAERUM P, HOLST D, RISE J.Dental Health in Trondelag 1983, Changes from 1973-1983. Oslo : Directorate of Health, 1985.
• BERGSTRÖM J. Cigarette smoking as a risk factor in chronic periodontal disease. Comm Dent Oral Epidemiol 1989;17:245-247.
• BERGSTRÖM J, ELIASSON S, PREBER H. Cigarette smoking and periodontal bone loss. J Periodontol 1991;62:242-246.
• BREIVIK T, THRANE PS, MURISON R, GJERMO P. Emotional stress effects on immunity, gingivitis and periodontitis. Eur J Oral Sci 1996;104:327-334.
• BURT BA. The distribution of periodontal destruction in industrial countries. In : Markers of disease susceptibility and activity of periodontal diseases. Johnson NW, ed. Cambridge : Cambridge University Press, 1990.
• CLEREHUGH V, LENNON MA, WORTHINGTON HV. 5-year results of a longitudinal study of early periodontitis in 14- to 19-year-old adolescents. J Clin Periodontol 1990;17:702-708.
• CROUCHER R, MARCENES WS, TORRES MCMB, HUGHES F, SHEIHAM A. The relationship between life-events and periodontitis. A case-control study. J Clin Periodontol 1997;24:39-43.
• FREITAS E, MEYER K, DAVIS RK, KRISTOFFERSEN T. A baseline study of periodontal conditions among youths and adults in Portugal. Comm Dent Oral Epidemiol 1983;11:250-254.
• GAENGLER P, GOEBEL G, KURBAD A, KOSA W. Assessment of periodontal disease and dental caries in a population survey using the CPITN, GPM/T and DMF/T indices. Comm Dent Oral Epidemiol 1988;16:236-239.
• GJERMO P. Goals for periodontal health and acceptable levels of disease. Means and methods in comm strategies. In : Public Health Aspects of Periodontal Disease in Europe. Frandsen A, ed. Berlin : Quintessence, 1984.
• GJERMO P. Factors influencing the assessment of treatment needs. J Clin Periodontol 1991;18:358-361.
• HANSEN BF, BJERTNESS E, GJERMO P. Changes in periodontal disease indicators in 35-year-old Oslo citizens from 1973 to 1984. J Clin Periodontol 1990;17:249-254.
• HANSEN BF, BJERTNESS E, GRÖNNESBY JK, ERIKSEN HM. Changes in periodontal treatment needs. A follow-up study of Oslo citizens from the age of 35 to 50 years. J Periodontal Res 1995;30:410-417.
• HOHLFELD M, BERNIMOULIN JP. Application of the community periodontal index of treatment needs (CPITN) in a group of 45-54-year-old German factory workers. J Clin Periodontol 1993;20:551-556.
• HUGOSSON A, JORDAN T. Frequency distribution of individuals aged 20-70 years according to severity of periodontal disease. Comm Dent Oral Epidemiol 1982;10:187-192.
• HUGOSSON A, KOCH G, BERGENDAL T, HALLONSTEN AL, SLOTTE C, THORSTENSSON B, THORSTENSSON H. Oral health of individuals aged 3-80 years in Jönköping, Sweden in 1973, 1983 and 1993. II. Review of clinical and radiographic findings. Swed Dent J 1995;19:243-260.
• JOHNSON N. Risk factors and diagnostic tests for destructive periodontitis. In : Proceedings of the 1st European Workshop on Periodontology. Lang NP, Karring T, eds. London : Quintessence Publishing Co Ltd, 1994.
• KÄLLESTÅL C, MATSSON L. Periodontal conditions in a group of Swedish adolescents. II. Analysis of data. J Clin Periodontol 1990;17:609-612.
• KÄLLESTÅL C, MATSSON L, HOLM AK. Periodontal conditions in a group of Swedish adolescents. I. A descriptive epidemiological study. J Clin Periodontol 1990;17:601-608.
• KIRKEGAARD E, BORGNAKKE WS, GRÖNBAEK L. Oral Health Status, Dental Treatment Need, and Dental Care Habits in a Representative Sample of the Adult Danish Population. Survey of Oral Health of Danish Adults. Århus : AV-centralen, Århus Tandlaegehöjskole, 1986.
• KLOCK KS, HAUGEJORDEN O. Primary reasons of extraction of permanent teeth in Norway : Changes from 1968 to 1988. Comm Dent Oral Epidemiol 1991;19:336-41.
• LÖE H, ANERUD A, BOYSEN H. The natural history of periodontal disease in man : prevalence, severity, and extent of gingival recession. J Periodontol 1992;63:489-495.
• MARKKANEN H, RAJALA M, PAUNIO K. Periodontal treatment need of the Finnish population aged 30 years and over. Comm Dent Oral Epidemiol 1983;11:25-32.
• MICHEELIS W, BAUCH J. Oral health of representative samples of Germans examined in 1989 and 1992. Comm Dent Oral Epidemiol 1996;24:62-67.
• MENGEL R, KOCH H, PFEIFER C, FLORES-DE-JACOBY L. Periodontal health of the population in eastern Germany (former GDR). J Clin Periodontol 1993;20:752-755.
• MILLER NA, BENAMGHAR L, ROLAND E, MARTIN J, ABT F. An Analysis of the CPITN periodontal treatment needs in France. Comm Dent Health 1987;4:415-423.
• NEUMANN PE, WANDELT D, WOLTZ H. Der Einfluss langjäriger stomatologischer Dispensairebetreuung Erwachsener auf die Epidemiologie von Periodontalerkranungen. Stomatol DDR, 1989;39:729-732.
• PAGE RC. Gingivitis. J Clin Periodontol 1986;13:345-359.
• PAPAPANOU PN.Epidemiology and natural history of periodontal disease. In : Proceedings of the 1st European Workshop on Periodontology. Lang NP, Karring T, eds. London : Quintessence Publishing Co Ltd, 1994.
• PILOT T, MIYAZAKI H. Periodontal conditions in Europe. J Clin Periodontol 1991;18:353-357.
• PLANCAK D, AURER-KOZELJ J. CPITN assessment of periodontal treatment needs in the population of Zagreb, Croatia. Int Dent J 1992;42:441-444.
• PRAYITNO SW, ADDY W, WADE WG. Does gingivitis lead to periodontitis in young adults ? Lancet 1993, 342:471-472.
• SCHÜRCH JR E, MINDER CE, LANG NP, GEERING AH. Periodontal conditions in a randomly selected population in Switzerland. Comm Dent Oral Epidemiol 1988;16:181-186.
• SHEIHAM A, SMALES FC, CUSHING AM, COWELL CR. Changes in periodontal health in a cohort of British Workers over a 14-year period. Brit Dent J 1986;143:125-127.
• SKALERIC U, KOVAC-KAVCIC M. Periodontal treatment needs in a population of Ljubljana, Yugoslavia. Comm Dent Oral Epidemiol 1989;17:304-306.
• STROHMENGER L, CERATI M, BRAMBILLA E, MALERBA A, VOGEL G. Periodontal epidemiology in Italy by CPITN. Int Dent J 1991;41:313-315.
• WORLD HEALTH ORGANIZATION. Periodontal Profiles, Geneva, World Health Organization, 1994.