Regional differences in the incidence of rheumatoid arthritis in Finland in 1995

Geographic Variation and Bias in the Polygenic Scores of Complex Diseases and Traits in Finland

Polygenic scores (PSs) are becoming a useful tool to identify individuals with high genetic risk for complex diseases, and several projects are currently testing their utility for translational applications. It is also tempting to use PSs to assess whether genetic variation can explain a part of the geographic distribution of a phenotype. However, it is not well known how the population genetic properties of the training and target samples affect the geographic distribution of PSs. Here, we evaluate geographic differences, and related biases, of PSs in Finland in a geographically well-defined sample of 2,376 individuals from the National FINRISK study. First, we detect geographic differences in PSs for coronary artery disease (CAD), rheumatoid arthritis, schizophrenia, waist-hip ratio (WHR), body-mass index (BMI), and height, but not for Crohn disease or ulcerative colitis. Second, we use height as a model trait to thoroughly assess the possible population genetic biases in PSs and apply similar approaches to the other phenotypes. Most importantly, we detect suspiciously large accumulations of geographic differences for CAD, WHR, BMI, and height, suggesting bias arising from the population's genetic structure rather than from a direct genotype-phenotype association. This work demonstrates how sensitive the geographic patterns of current PSs are for small biases even within relatively homogeneous populations and provides simple tools to identify such biases. A thorough understanding of the effects of population genetic structure on PSs is essential for translational applications of PSs.

Incidence of Chronic Persistent Rheumatoid Arthritis and the Impact of Smoking: A Historical Twin Cohort Study

OBJECTIVE

To assess the incidence of chronic persistent rheumatoid arthritis (RA) in a population-based cohort of twins and to determine the impact of smoking.

METHODS

In a historical cohort study on twins born in 1920 to 1982, we identified 157 cases of RA among 45,280 responders (response rate 80%). Information on smoking was obtained by questionnaire and interview. A mixed-effects Poisson regression model was used to estimate incidence rate ratios with age, sex, smoking duration, and smoking intensity as covariates. We used the SplitLexis procedure in the Epi R package to study a possible effect of period or cohort in addition to age on the variation of the incidence.

RESULTS

The annual incidence of chronic persistent RA was 18.8 per 100,000 person-years, ages 15-73 years (females 25.2, males 12.0), increasing with age to a maximum at age 60 years in females and age 70 years in males. The incidence rate ratio among ever-smoking patients was 1.96 (95% confidence interval [95% CI] 1.43-3.76), 1.93 (95% CI 1.00-3.7) after 30 pack-years, and 1.034 (P < 0.001) per year of smoking, implying a doubling of risk after 20 years regardless of sex and smoking intensity. We did not detect significant period or cohort effects.

CONCLUSION

The incidence of chronic persistent RA is lower than the incidence figures reported in inception cohorts. Smoking duration, but not intensity, doubled the risk of RA after 20 years of smoking in both sexes.

The need to address the burden of musculoskeletal conditions

Musculoskeletal conditions are common in men and women of all ages across all socio-demographic strata of society. They are the most common cause of severe long-term pain and physical disability and affect hundreds of millions of people around the world. They impact on all aspects of life through pain and by limiting activities of daily living typically by affecting dexterity and mobility. They affect one in four adults across Europe [1]. Musculoskeletal conditions have an enormous economic impact on society through both direct health expenditure related to treating the sequelae of the conditions and indirectly through loss of productivity. The prevalence of many of these conditions increases markedly with age, and many are affected by lifestyle factors, such as obesity and lack of physical activity. The burden of these conditions is therefore predicted to increase, in particular in developing countries. The impact on individuals and society of the major musculoskeletal conditions is reviewed and effective prevention, treatment and rehabilitation considered. The need to recognise musculoskeletal conditions as a global public health priority is discussed.

Self-reported flaring varies during the menstrual cycle in systemic lupus erythematosus compared with rheumatoid arthritis and fibromyalgia

OBJECTIVE

We studied self-reported flares before menses in SLE, RA and FM, and determined whether there were differences.

METHODS

Part 1: women blinded to study hypothesis having menses with SLE and RA completed a 100-day diary logging their pain, fatigue and disease activity on a 100-mm visual analogue scale (VAS) and menses. Part 2: SLE, RA and FM patients were mailed a questionnaire about menstrual cycle and disease changes.

RESULTS

Part 1: 28 patients with SLE and 21 with RA were included; 84% of SLE and 71% of RA patients had regular menses. Patients with SLE had higher pain, fatigue and disease activity during menses than in the hormonal surge phase. Patients with RA had increased pain, fatigue and disease activity during decreasing progesterone. Part 2: 498 patients were surveyed, of whom 56% responded (81 SLE, 136 RA and 61 FM). Those taking the oral contraceptive pill (OCP) ever since diagnosis were 52% with SLE, 41% with RA and 33% with FM (P = 0.1). Those who flared before menses when not on OCP were 36% with SLE, 28% with RA and 54% with FM (P = 0.08). In SLE patients, the mean VAS scores were worse during menses with average scores of 21.0 for pain, 26.7 for fatigue and 18.2 for disease activity vs 16.0 (P = 0.04), 18.6 (P = 0.004) and 11.4 (P = 0.01) during the surge. In RA, the decreasing progesterone phase was different from the increasing oestrogen phase for pain (P = 0.06).

CONCLUSION

There could have been recall bias and participants may have confused pre-menstrual syndrome with flares. However, there seem to be menstrual cycle flares in SLE, RA and FM.

Early rheumatoid arthritis in Italy: study of incidence based on a two-level strategy in a sub-area of Florence (Scandicci-Le Signe)

The concept of Early Arthritis represents a new diagnostic-therapeutic strategy in modern rheumatology. Even if many Early Arthritis clinics are starting up, we do not yet know the frequency of this pathology in the Italian population. With the collaboration of 20 general practictioners (GPs) operating in the municipalities of Scandicci, Lastra a Signa and Signa, we assessed the incidence of rheumatoid arthritis and of new cases of Early Rheumatoid Arthritis (ERA) in the period from 1.09.2005 to 31.08.2006. The general population over 18 years old in the three municipalities according to the political electoral lists in April 2006 was as follows: Scandicci 42,474 (Males 20,290; Females 22,184), Lastra a Signa 15,368 (M 7,458; F 7,910) and Signa 13,372 (M 6,439; F 6,933). The total number of patients followed by the 20 GPs was 32,521 according to the records of ASL10 Florence. In one year 920 patients were referred by their GPs to a rheumatologist with suspected early undifferentiated arthritis according to Emery's criteria. The patients underwent a rheumatological examination and the rheumatoid factor IgM, hidden rheumatoid factors (IgG and IgA) and IgG antibodies anti-CCP (anti-cyclic citrullinate peptides) with a semiquantitative immuno-enzymatic test ELISA were investigated. In one year we observed 32 new cases of Rheumatoid Arthritis, of which 8 were males and 24 were females. The rate of incidence with respective intervals of confidence of 95% was 0.98 per thousand (0.64-1.32 per thousand). The average age was 47.7 +/- 10.5 in the females and 54.9 +/- 10.3 in the males. The patients had an average history of illness in months of 5.2 +/- 1.3 F versus 4.6 +/- 1.1 M, number of tender joints 6.2 +/- 2.3 F versus 5.3 +/- 2.2 M, number of swollen joints 4.8 +/- 1.4 F versus 4.2 +/- 1.5 M, a global assessment of 64.3 +/- 10 F versus 53 +/- 12 M, ESR (mm/h) 49.2 +/- 11.3 F versus 43.3 +/- 12.5 M, CRP (mg/dl) 2.8 +/- 1.3 F versus 2.3 +/- 1.4 M, DAS28 5.55 +/- 1.2 F versus 5.19 +/- 1.3 M, HAQ 2.5 +/- 0.4 F, 2.2 +/- 0.3 M. The rates of incidence in the Italian population affected by early rheumatoid arthritis are higher than those found in some European populations, such as those of the UK and Finland, but less than those found in the population of USA. The different data reported in the literature seem to be due to the different methods of assessing ERA and to the different types of samples studied.

Incidence and Prevalence of Rheumatoid Arthritis, Based on the 1987 American College of Rheumatology Criteria: A Systematic Review

OBJECTIVES

To conduct a systematic review of incidence and prevalence studies of rheumatoid arthritis (RA), based on the 1987 revised American College of Rheumatology (ACR) criteria, to compare their methodologies and summarize their results, and to investigate the possible geographic variations and changes over time in the frequency of the disease.

METHODS

We conducted a Medline search between January 1988 and December 2005. Studies reporting the incidence and prevalence of RA in adult populations (16 to 20 years and over), based on 1987 ACR criteria, were eligible for inclusion. From each study included, we extracted the country, year of publication, type of study (retrospective, prospective, or cross-sectional), and incidence or prevalence rates. The study areas were grouped into (a) North American countries; (b) north European countries; (c) south European countries; and (d) developing countries. We examined the geographical differences of prevalence and incidence rates using the Mann-Whitney and the Kruskall-Wallis tests.

RESULTS

A total of 28 studies were identified meeting the inclusion criteria. Nine were incidence studies, 17 were prevalence studies, and 2 estimated both prevalence and incidence rates. Incidence studies were not available from developing countries. There is a significant difference of prevalence estimates between northern European and American countries and developing countries. South European countries have lower median incidence rates than North American and north European countries. As concerning the time trends of RA occurrence, only 3 incidence studies provided secular data from the same study area, based on ACR criteria, using the same methods of case ascertainment. Two of these studies indicate a decreasing incidence of RA in Finland and United States of America.

CONCLUSIONS

The occurrence of RA varies among countries and areas of the world. A decreasing trend has been observed in countries characterized by high rates of RA incidence and prevalence. However, the relatively small number of studies for most areas of the world and the lack of incidence studies for the developing countries limits the understanding of worldwide RA epidemiology.

Total hip arthroplasty in Denmark: incidence of primary operations and revisions during 1996-2002 and estimated future demands

BACKGROUND

The annual number of total hip arthroplasties (THA) has increased in Denmark over the past 15 years. There is, however, limited detailed data available on the incidence of THAs.

METHODS

We calculated the incidence rates (IR) of primary THA and revision in Denmark between 1996 and 2002 and estimated the demands for primary THA in Denmark until 2020. We used data from the Danish Hip Arthroplasty Registry, a nationwide and population-based clinical database, to identify patients who had undergone primary THA (n = 37,144) or revision arthroplasties (n = 6446). Age and sex-specific data on the Danish population were obtained from the StatBank Denmark. All IRs were standardized according to two standards, i.e. the Danish population in 1996 and the European standard population (18 age groups). The future demands for primary THA were estimated using the age and sex-specific incidence of primary THA for 2002 as a reference, and taking into account the expected changes in the age distribution of the population and the trend in IRs seen in Denmark between 1996 and 2002.

RESULTS

The annual overall standardized IRs of primary THAs and revisions increased from 101 (95% confidence interval (CI): 97.6-104) to 134 (CI: 131-138) and from 19.2 (CI: 17.9-20.5) to 21.1 (CI: 19.8-22.4) per 100,000 inhabitants from 1996 to 2002, respectively (IRs adjusted to the Danish population in 1996). The IRs of primary THAs and revisions increased by 30% and 10% during this period. The relative increase in IRs of primary THAs was found to be similar in both women and men. The increase was higher among patients aged 50-59 years, however. Furthermore, a decrease in IRs was seen in patients who underwent primary THA due to rheumatoid arthritis. IRs of primary THAs have been estimated to increase by 22% in 2020 compared with 2002, based only on the expected changes in the age distribution of the population. However, assuming that the annual age and sex-independent increase in the IRs seen in the period 1996-2002 will continue, the IR of primary THA is estimated to increase by as much as 210% in 2020.

INTERPRETATION

The overall annual standardized IRs of primary THAs and revisions in Denmark increased during the period from 1996 to 2002. Moreover, the demands for THA procedures in the coming decades may exceed the current capacity due to the ageing population and a continued age and sex-independent increase in surgical activity.

Prevalence of rheumatoid arthritis in France: 2001

BACKGROUND

Prevalence estimates of rheumatoid arthritis (RA) vary across Europe. Recent estimates in southern European countries showed a lower prevalence than in northern countries.

OBJECTIVES

To estimate the prevalence of RA in France in a multiregional representative sample in the year 2001.

METHODS

A two stage random sample was constituted in seven areas (20 counties) from the national telephone directory of households and by the next birthday method in each household. Patient-interviewers, member of self help groups, were trained to administer telephone surveys using a validated questionnaire for case detection of inflammatory rheumatism, and conducted the survey under quality control. All suspected cases of RA were confirmed by their rheumatologist or by clinical examination. Prevalence estimates after probability sampling correction were standardised for age and sex (national census 1999).

RESULTS

An average response rate of 64.7% (two stages combined) led to a total of 9395 respondents. Standardised prevalence was 0.31% (95% confidence interval 0.18 to 0.48) for RA, 0.51% in women and 0.09% in men, with a higher age-specific prevalence in the 65-74 year age band. A geographical analysis of county clustering showed significant variation across the country.

CONCLUSION

This national multiregional cooperative study demonstrates the usefulness of working in association with patients of self help groups. It showed a similar prevalence of RA to that of the spondyloarthropathies estimated concomitantly during the survey. It provides a reliable basis for definition of population targets for healthcare delivery and drug treatments.

National databases and rheumatology research I: longitudinal databases in Scandinavia

Nationwide population-based longitudinal databases provide excellent resources for medical research in Scandinavia. These include the Population Registry, the Cancer Registry, the Cause of Death Registry, the Hospital Discharge Registry, and other registers, and are linkable to each other by the personal identification code. The registers have long historical backgrounds, and are regulated strictly by law. This article describes features of the national databases and provides some examples of rheumatology research that use these databases.