Bramell-Risberg et al digital stopwatch was used. For the TUG and walking test at self-selected speed, the instructions were to walk at a normal, comfortable speed; for fast speed, the instructions were to walk as fast as possible without running. The walking test was performed in a hospital corridor; this test was not carried out in the participants’ homes. The subjects were allowed to rest for approximately 2 minutes between each test. The TUG test and walking 2 × 15 m, including a 180° turn, were performed first at the self-selected speed and then at maximal (fast) walking speed. Subjects who performed the TUG and walking tests with walking aids were not included in the analysis. Covariates Sociodemographic data included age, sex, marital sta- tus, place of residence, and education. Functional status included data on walking ability, personal activities of daily living (P-ADL), and instrumental activities of daily living (I-ADL).38 P-ADL included bathing, dressing, toileting, ris- ing from bed/chair, continence, and feeding, while I-ADL included cleaning, shopping, transportation, and cooking. Detailed descriptive data are provided in Tables 1 and 2. Health status included smoking and drinking habits and physical activity during the past year (Table 2). Comorbidity was based on questions regarding specific diseases, medical history, medication, clinical examination, and questionnaires. Comorbidity was classified according to the International Classifications of Diseases and Related Health problems, and congestive heart failure was classified according to the New York Heart Association criteria39 (Table 2). Physiological mea- sures included anemia, defined by the Department of Clinical Chemistry, Malmö University Hospital as ,117 g/dL hemoglo- bin (Hb) for women and ,134 g/dL Hb for men, and body mass index, computed as weight in kilograms divided by the square of height in meters (Table 2). Data on sociodemographics, health-related factors, and functional status were self-reported. Medical assessment was performed by a physician, and cogni- tive function was assessed by a specially trained behaviorist in psychology. Assessment of pain and physical performance tests were conducted by trained, registered nurses. All subjects were asked if they experienced pain in their back or in any joints of the lower extremities during rising, standing, walking, and climbing stairs. Pain was dichotomized into yes/no. Joint pain in the legs was not differentiated according to joint. Statistical analysis Differences between the three groups were assessed with a Chi-square test and regression analysis. Comparisons were made between groups for the variables listed in Table 2. 198 submit your manuscript | www.dovepress.com Dovepress Dovepress Table 1 Characteristics of the participants (n = 2115) Cases Intermediates Controls n = 328 n = 457 n = 1330 Age, mean ± SD 75.8 ± 10.2 71.8 ± 9.5 69.0 ± 9.1 Male/female (%) (50.9/49.1) (50.1/49.9) (43.5/56.5) Age groups, n (%) Males 60–69 years 64 (38.3) 129 (56.3) 398 (68.9) 70–79 years 46 (27.5) 51 (22.3) 92 (15.9) $80 years 57 (34.1) 49 (21.4) 88 (15.2) Females 60–69 years 45 (28.0) 86 (37.7) 456 (60.6) 70–79 years 33 (20.5) 75 (32.9) 130 (17.3) $80 years 83 (51.6) 67 (29.4) 166 (22.1) Marital status, n (%) Married/cohabiting 155 (47.8) 269 (59.5) 810 (61.2) Widow/widower 107 (33.0) 92 (20.4) 225 (17.0) Divorced/not cohabiting 41 (12.7) 66 (14.6) 197 (14.9) Unmarried 21 (6.5) 25 (5.5) 91 (6.9) Place of residence, n (%) Rural 30 (9.3) 44 (9.8) 132 (10.0) Urban 294 (90.7) 407 (90.2) 1190 (90.0) Walking ability, n (%) Independent walking 271 (82.6) 414 (90.6) 1229 (92.4) Dependent on walking 57 (17.4) 43 (9.4) 101 (7.6) aids/wheelchair P-ADL, n (%) Dependent in 310 (98.7) 438 (99.1) 1304 (99.7) #1 activity I-ADL, n (%) Dependent in 293 (92.7) 410 (94.0) 1239 (95.6) #1 activity Abbreviations: SD, standard deviation; P-ADL, personal activities of daily living; I-ADL, instrumental activities of daily living. Confounders with a P-value below 0.05, listed in Table 2, were adjusted for in the model. The association between cognitive impairment, categorized into three groups, as the dependent variable, and the results of physical performance tests, as independent variables, was tested using an ordinal regression model. A separate regression model was com- puted for each test, including adjustment for confounders. To reduce the effect of skewed distribution of the results of the OLS test, the data were categorized into time categories used by others to assess balance.40–42 Table 3 presents descriptive data from the performance of physical tests for cases, intermediates, and controls, strati- fied according to age. No further stratification was made, due to the limited numbers in each group. For the physical performance tests significantly related to the grouping vari- able in the ordinal regression models, additional analysis was performed to study the extent of the association between them and cognitive impairment. A general linear model was employed, using each test as the dependent variable and Clinical Interventions in Aging 2012:7