透析開始時の低栄養と死亡率

透析開始時の低栄養と血清アルブミン値は死亡率の独立した予測因子であるという10年間のコホート研究を紹介します。

Maria Chan, et al: Malnutrition (Subjective Global Assessment) Scores and Serum Albumin Levels, but not Body Mass Index Values, at Initiation of Dialysis are Independent Predictors of Mortality: A 10-Year Clinical Cohort Study. Journal of renal nutrition, http://dx.doi.org/10.1053/j.jrn.2011.11.002

リサーチクエスチョンは以下の通りです。

P：透析開始した患者で
E：低栄養、血清アルブミン値が低い場合、
C：栄養状態良好、血清アルブミン値が正常の場合と比較して、
O：死亡率が高い

研究デザインは後ろ向きコホート研究です。

結果ですが、透析導入後の生存期間の中央値は54.2か月（約4.5年）で、透析開始時に52.1％がSGAで低栄養と判定されました。高齢、末梢血管疾患、血清アルブミン低値、低栄養が独立した死亡の予測因子でした。一方、BMIは死亡と有意な関連を認めませんでした。

今回の研究ではObesity Paradoxを認めませんでしたが、SGAで低栄養であれば生命予後が悪いということは明らかになりました。血清アルブミン値は栄養指標とはいえませんが、予後指標としてはやはり有用です。サルコペニアの有無で死亡率が異なるかどうかを知りたいですね。

Objective
To examine the associations between demographic, clinical, lifestyle, and nutritional parameters at the start of dialysis and mortality, including the combined effects on nutritional parameters, which were seldom investigated in the literature.

Design
Ten-year retrospective clinical cohort study.

Setting
Dialysis unit of a metropolitan tertiary teaching hospital in Sydney, Australia.

Subjects
Incident dialysis patients (n = 167; hemodialysis, 57.5%; male, 61.7%; age, 65.3 ± 13.6 years; diabetic, 24.5%) who commenced on a planned dialysis program.

Methods
Associations were examined between all-cause mortality and baseline demographics, including age and gender; clinical and lifestyle characteristics, including glomerular filtration rate, smoking habits, presence of comorbidities (e.g., coronary artery disease, diabetes mellitus, and peripheral vascular disease); and nutritional parameters, including body mass index (BMI), serum albumin (s-albumin) levels, and subjective global assessment score (SGA). Associations with combination values for malnutrition, s-albumin (<3.3 vs. ≥3.3 g/dL), and BMI (<26 vs. ≥26 kg/m2) were also examined.

Results
Median survival was 54.2 months (interquartile range, 23 to 83), and 52.1% of patients were malnourished (SGA score B and C) at the start of dialysis. Advanced age (classified as >65 years, P < .0001), presence of peripheral vascular disease (P < .0001), reduced s-albumin levels (P = .01), and malnutrition scores (P = .02) independently predicted mortality. Being overweight and obese (BMI: ≥26 kg/m2) did not show any advantage on survival (P = .73). Being malnourished and overweight (or obese) was associated with a 3-fold increase in mortality risk (adjusted hazard ratio [HR], 2.96; 95% confidence interval [CI], 1.12 to 7.33; P = .02) compared with being well nourished with a BMI <26 kg/m2 (referent). Compared with being well nourished (SGA = A), being malnourished with normal or low s-albumin was associated with higher risk (HR, 2.06; 95% CI, 1.06 to 4.00; P = .03 and HR, 2.86; 95% CI, 1.65 to 4.94; P < .0001, respectively). There was no statistical difference between mortality risks through any combination of s-albumin and BMI values (P = .54).

Conclusion
Malnutrition and reduced s-albumin levels were found to be independent predictors of mortality, whereas being overweight and obese did not show protective effects.