[Validity of body fat estimation by near infrared spectroscopy in long-term care elderly patients: a comparison with skinfold thickness].

Aim: The aim of this study was to examine the validity of body fat measurement by near infrared spectroscopy (NIRS) in long-term care elderly patients.

Methods: The subjects were 59 elderly patients (23 men, 36 women, age 82.0+/-6.6 years) and 38 healthy young persons (19 men, 19 women, age 28.1+/-6.1 years). Percentage of body fat (%BF), body fat mass (BFM), and lean body mass (LBM) were estimated by NIRS and skinfold thickness (SF). Body fat was compared by genders and between the elderly patients and the healthy young subjects. The relationship between NIRS and SF of the elderly patients was compared with that of the healthy young subjects.

Results: Means of body fat variables of the elderly patients by NIRS were: %BF 18.6%, BFM 8.8 kg, LBM 37.7 kg for men; and %BF 26.0%, BFM 10.7 kg LBM, 29.6 kg; for women. The %BF and BFM values estimated by NIRS were significantly greater than the respective values measured by SF; LBM estimated by NIRS was significantly less than that by SF. These results show that body fat measured by SF may be undervalued. The correlation between NIRS and SF was significant (r > or =0.49, p < or =0.05), and the regression lines for the elderly patients and the healthy young were not significantly different. Body fat of elderly patients by NIRS may be similar to that of healthy young by SF.

Conclusions: The results suggest that NIRS yields higher values than SF in measurement of body fat in long-term care elderly patients.