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Assessment of depression in Kuwait by principal component analysis.

One hundred depressed inpatients were examined by the WHO schedule for Standardized Assessment of Depressive Disorders (SADD). A common core of symptoms is shared with patients in other studies from Western, Middle-Eastern and international studies. However, pathoplastic cultural influences are manifest in a number of symptoms, notable among which are metaphorical descriptions of symptom intensity by the overwhelmed patient, infrequency of feelings of hopelessness and suicidal attempts, masking of guilt feelings by a front of somatization and a linkage of body weight and sexual functions to health in general. Evidence is provided for a continuum-type unimodal distribution of the principal components studied.

Adult↗
PubMed1991

Principal components analysis of regional bone density in black and white women: relationship to body size and composition.

Black and white women in the United States differ with respect to bone mass and the risk of developing osteoporosis. It has been suggested that greater body size among U.S. blacks may contribute to greater bone density in this group. It is not known whether the fat or lean component contributes more to this relationship. Bone density was measured at seven sites in 161 normal black and white women using single and dual photon absorptiometry. The first principal component accounted for 73% of the variance in the sample and constitutes an index of skeletal mass. The second principal component added another 10% and contrasts the axial and appendicular sites. Both the regional bone densities and the first principal component showed significantly greater bone densities for blacks; adjustment for body size reduced bone mass differences by approximately 50%. Body composition analysis done on a subset of these women indicated that the fat component of body mass may be the more important factor in its effect on bone mass.

Absorptiometry, Photon↗
PubMed2004

Perceived cognitive function is a major determinant of health related quality of life in a non-selected population of patients with coronary artery disease--a principal components analysis.

OBJECTIVE: To assess health related quality of life (HRQL) and explore its underlying structure in a non-selected population of patients with coronary artery disease (CAD). DESIGN, SETTING AND SUBJECTS: HRQL was estimated by the disease specific Cardiac Health Profile (CHP) questionnaire and the EuroQol-VAS (EQ) in 253 consecutive unselected CAD patients in Södertälje, Stockholm County, Sweden. Explorative factor analysis was used to identify independent dimensions of HRQL. Current angina was ranked according to Canadian Cardiovascular Society Classification (CCS). RESULTS: Four independent principal factors representing perceived cognitive, physical, social and emotional functions underlying the patients' HRQL were found. Identical factors were recognized with an alternate technique. The major factor--explaining 43 % of HRQL--was perceived cognitive function reflecting ability to concentrate, activity drive, memory and problem solving. Cognitive function correlated to EQ but not to CCS. Perceived physical function/general health explained 9% of HRQL and was as expected related both to EQ and CCS. Total CHP scores differed significantly to those of healthy controls. CONCLUSIONS: Perceived cognitive function seems to be a major determinant of HRQL in CAD patients. This, in addition to earlier reports of possible prognostic information of reduced cognitive function, would prompt us to propose that HRQL assessments should include questions aimed to assess cognitive function.

Aged↗
PubMed1985

Principal-components analysis of Brazilian Indian anthropometric data.

Analysis of nine characteristics on 1,205 males and 932 females from 12 tribes or groups of tribes indicated a poor relationship between morphology and language, as well as moderate agreement with the variability expected considering geography only. Two samples in the Xingu area studied during an interval of half a century (1897-1947) showed remarkable similarity. The conformity of the Caingang morphology with those of other tribes and the distinctiveness of the Xavante and Tenetehara has been amply confirmed.

Anthropometry↗
PubMed1986

Principal component analysis of event-related potentials: a note on misallocation of variance.

Wood and McCarthy (1984) found a 'misallocation of variance' when applying PCA, including Varimax rotation, to simulated data. Here it is demonstrated that this effect can be produced by Varimax rotation, without PCA as an intervening step. PCA does not distort or lose information when extracting components, since it is shown that the prototypes may be perfectly reconstructed from the unrotated solution. However, it is stressed that infinitely many sets of prototypes may render the same final solution, a fact which cannot be overcome by any method. The role of the rotation step within this framework is discussed.

Electroencephalography↗
PubMed2005

Reference-free quantification of EEG spectra: combining current source density (CSD) and frequency principal components analysis (fPCA).

OBJECTIVE: Definition of appropriate frequency bands and choice of recording reference limit the interpretability of quantitative EEG, which may be further compromised by distorted topographies or inverted hemispheric asymmetries when employing conventional (non-linear) power spectra. In contrast, fPCA factors conform to the spectral structure of empirical data, and a surface Laplacian (2-dimensional CSD) simplifies topographies by minimizing volume-conducted activity. Conciseness and interpretability of EEG and CSD fPCA solutions were compared for three common scaling methods. METHODS: Resting EEG and CSD (30 channels, nose reference, eyes open/closed) from 51 healthy and 93 clinically-depressed adults were simplified as power, log power, and amplitude spectra, and summarized using unrestricted, Varimax-rotated, covariance-based fPCA. RESULTS: Multiple alpha factors were separable from artifact and reproducible across subgroups. Power spectra produced numerous, sharply-defined factors emphasizing low frequencies. Log power spectra produced fewer, broader factors emphasizing high frequencies. Solutions for amplitude spectra showed optimal intermediate tuning, particularly when derived from CSD rather than EEG spectra. These solutions were topographically distinct, detecting multiple posterior alpha generators but excluding the dorsal surface of the frontal lobes. Instead a low alpha/theta factor showed a secondary topography along the frontal midline. CONCLUSIONS: CSD amplitude spectrum fPCA solutions provide simpler, reference-independent measures that more directly reflect neuronal activity. SIGNIFICANCE: A new quantitative EEG approach affording spectral components is developed that closely parallels the concept of an ERP component in the temporal domain.

Adolescent↗