Osteoarthritis and Frailty in Elderly Individuals Across Six European Countries

Results From the European Project on OSteoArthritis (EPOSA)

Maria Victoria Castell; Suzan van der Pas; Angel Otero; Paola Siviero; Elaine Dennison; Michael Denkinger; Nancy Pedersen; Mercedes Sanchez-Martinez; Rocio Queipo; Natasja van Schoor; Sabina Zambon; Mark Edwards; Richard Peter; Laura Schaap; Dorly Deeg

Disclosures

BMC Musculoskelet Disord. 2015;16(359) 

In This Article

Methods

Study Design and Participants

The EPOSA project involves six cohort studies, each performed in a different country: Germany (The study on Activity and Function in the Elderly in Ulm, ActiFE-Ulm), the United Kingdom (UK) (Hertfordshire Cohort Study, HCS), the Netherlands (Longitudinal Aging Study Amsterdam, LASA), Italy (Godega di Sant'Urbano, Veneto Region), Spain (Ageing in Peñagrande), and Sweden (Swedish Twin Register). Random samples from these population-based cohorts were included. In each cohort, around 750 potential participants were contacted with the aim of recruiting 500 participants. In Italy, a new sample was drawn, with recruitment procedures and age/sex-distributions similar to those in the other studies. A total of 2,942 respondents (response rate ranging from 64.6 % to 82.2 %, averaging 72.8 %) were included in the EPOSA baseline study. The overall age range was 65–85 years (with oversampling of the oldest respondents) in all cohorts except for the UK, in which the age range was 71–79 years.

A detailed description of the study design and data collection of the EPOSA study is described elsewhere.[22] All participants completed an informed consent. For all six countries, the study design and procedures were approved by the Medical Ethics committee of the respective centers (Germany: Ethical Committee of Ulm University; the Netherlands: Medical Ethical Committee of the VU University Medical Center; Spain: Ethic Committee for Clinical Research of University Hospital La Paz of Madrid; Sweden: Ethics Board of Karolinska Institutet; UK: The Hertfordshire Research Ethics Committee; Italy: Comitatio etico ULSS7).

It is a longitudinal study in which all the variables were collected primarily from March to November 2011, except for frailty which was collected one year later (between March and November 2012). The study population for the present analysis was made up of 2,455 individuals who participated in the baseline and the follow-up waves. 487 baseline participants (16.6 %) could not be included because they had died, were untraceable, or declined to participate one year later. The proportion of people aged 80–85 and of women in this group of non-respondents was higher than in participants (28.1 % vs 15.4 %, for age and 57.5 % vs 50.8 % for sex, respectively). The proportion of obese people in both samples was similar. A standardized questionnaire was applied and a clinical examination was performed. Participants were visited in their homes by trained research nurses, except for Italy and Spain, where participants were examined in a health care centre, and only disabled persons were visited in their home.

Study Variables/Measures

Data were collected on the following variables:

Clinical Osteoarthritis. Algorithms for clinical OA were developed based on the clinical classification criteria developed by the American College of Rheumatology (ACR).[23] Algorithms were specified both for site-specific OA (knee, hip and hand, respectively) and Clinical OA at any site (any of these three joints). The clinical diagnosis of knee OA was based on both history and physical examination: pain in the knee was evaluated by the Western Ontario and McMaster Universities OA Index (WOMAC) pain subscale score,[24] plus any three of: age 50 or over, morning stiffness lasting <30 min, evaluated by the WOMAC stiffness subscale (score from 'mild' to 'extreme'); crepitus on active motion in at least one side; bony tenderness in at least one side; bony enlargement in at least one side, and no palpable warmth of synovium in both knees. The clinical diagnosis of hip OA was based on both history and physical examination: pain in the hip was evaluated by the WOMAC pain subscale score, plus all of: pain associated with hip internal rotation in at least one side; morning stiffness lasting <60 min, evaluated by the WOMAC stiffness subscale (score from 'mild' to 'extreme'); and age 50 or over. The clinical diagnosis of hand OA was based on both history and physical examination: pain, aching or stiffness of the hand was evaluated by the Australian/Canadian OA Hand Index (AUSCAN) pain and stiffness subscale;[25] plus any two of: hard tissue enlargement of two or more of the 2nd and 3rd distal interphalangeal (DIPs), 2nd and 3rd proximal interphalangeal (PIPs), 1st carpometacarpal (CMC) joints of at least one hand; hard tissue enlargement of two or more DIPs of at least one hand; deformity of at least one of the 2nd and 3rd DIPs, 2nd and 3rd PIPs, 1st CMC joints of at least one hand. Swelling of the metacarpophalangeal (MCP) joints, which is also included in the ACR classification criteria as a control to exclude rheumatic arthritis, was only measured in the UK and Germany. The categorical variable Clinical OA-number of sites describes the number of joints involved, from 0 a 3 (knee, hip and/or hand)

Frailty was measured based on the five criteria proposed by Fried,[9] with some adaptation as follows:

1) Unintentional weight loss (Shrinking) of ≥5 % in the last year; 2) Low energy (Exhaustion) based on questions from the Centre for Epidemiologic Studies Depression Scale (CES-D); 3) Weakness: Grip strength in the dominant hand measured with a dynamometer (Jamar R) and adjusted for body mass index (BMI); 4) Slowness: Calculated after walking three meters, adjusted for sex and height. Participants were asked to "walk to the other end of the course as quickly as you can, but do not run" and were timed using a stopwatch. In the UK, the instruction was to "walk to the other end of the course at your usual speed, just as if you were walking down the street to go to a shop". In Germany, 361 of the participants were measured using a GAITRite® walkway system and were standardised using a stopwatch. Individuals included in the worst quintile in each country were considered to be slow. 5) Low physical activity: Kilocalories (kcal) expended per week were calculated based on the Longitudinal Ageing Study Amsterdam (LASA) Physical Activity Questionnaire (LAPAQ),[26] using self-reports about the frequency and duration of walking, cycling, gardening and engaging in sports. The cut-off points used in this case were the worst quintile in the EPOSA sample.

Persons who met at least three criteria were considered to be frail, those who met one or two criteria were prefrail, and those with none were considered non-frail. Accordingly, the variable frailty was divided into three categories.

Potential Co-variables

Demographic covariates such as age, gender and education level were collected. Education was measured by asking for the highest level of education completed and was categorized into "elementary school not completed", "elementary school completed", "vocational education/general secondary education", and "college or university education".

Health covariates: BMI was calculated as weight in kilograms divided by height in squared meters. Obesity was defined as BMI of 30 kg/m 2 or higher. Number of chronic conditions was measured through self-reported presence of the following chronic diseases or symptoms that lasted for at least 3 months or diseases for which the respondent had been treated or monitored by a physician: chronic non-specific lung disease, cardiovascular diseases, peripheral artery diseases, stroke, diabetes, cancer, and osteoporosis. Comorbidity was evaluated as the number of diseases, or defined as the occurrence of two or more coexisting conditions.

Country Covariate. Data from the cohorts of Germany, Italy, the Netherlands, Spain, Sweden and the United Kingdom were collected.

Statistical Methods

As age distribution and gender split varied between the cohorts of different countries, a weighting variable was created for each individual within each country. The weights were calculated per sex and per 5-year age groups, using the formula: W = Pexp/Pobs, where Pobs is the observed proportion of persons in a specific age/gender category in the cohort (n 1/n), and Pexp is the expected proportion of persons in a specific age/gender category in the population (N 1/N), taking the European Standard Population in 2010 as the reference population.[22] This technique allowed direct comparisons of the variables across countries.

A descriptive analysis was performed. For the continuous variables such as age, the mean and standard deviation were calculated. Categorical variables were expressed as absolute frequencies and their 95 % confidence intervals (95 % CI).

We calculated the frequency of frailty and OA in the study population and made a descriptive analysis of frailty by demographic (age, gender and educational level) and health-related variables (obesity, comorbidity, and OA). Differences among countries were assessed using Kruskal Wallis for age and the chi-squared test for categorical variables.

The association between OA and frailty was summarized with odds ratios (OR) and their 95 % confidence interval (CI) obtained from logistic regression. Multivariate analyses were conducted using the variable frailty with three categories (no frailty as reference variable, pre-frailty and frailty), as the dependent variable (multinomial logistic regression) and OA as the main independent variable, introducing in the model the co-variables that were associated with frailty at p < 0.10 in a bivariate analysis.

We conducted five regression analyses, using the previously described measures of OA (clinical OA at any site, knee OA, hip OA, hand OA and clinical OA-number of sites) in each analysis. All analyses were performed using SPSS for Windows version 19.0.

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