Obesity can benefit survival-a 9-year prospective study in 1614 Chinese nursing home residents

Objective: Weight loss has been considered predictive of early mortality in nursing home residents. Lower body mass index, irrespective of weight loss, has also been considered detrimental for survival in community-dwelling older persons. We examined which of the 2 is more important for survival in nursing home residents and at what body mass index (BMI) cut-offs survival benefits are gained or lost.

Design: Prospective study.

Setting: Nursing homes.

Participants: One thousand six-hundred fourteen nursing home residents.

Measurement: Minimum Data Set at baseline and mortality status assessed at 6 months, 1, 2, 4, and 9 years later. Relationship between mortality and significant weight loss (≥5% over 30 days or ≥10% over 180 days), and BMI, was studied by Cox regression with both variables in the same model, adjusted for age, sex, medical conditions (cancer, renal failure, heart disease, dementia, hip fracture, diabetes mellitus), tube-feeding, 25% food left uneaten, swallowing problem, and the activities of daily living hierarchy scale.

Results: One thousand six-hundred fourteen residents (69.5% female) with mean age 83.7 ± 8.4 years and mean BMI 21.7 ± 4.8 were studied. Mortality rates were 6.3% (6-month), 14.3% (1-year), 27.1% (2-year), 47.3% (4-year), and 78.1% (9-year). Significant weight loss was not associated with higher mortality at all follow-up durations, whereas higher BMI was significantly protective: mortality reduction per 1 unit increase in BMI were 9% at 6 months, 10% at 1 year, 9% at 2 years, 7% at 4 years, and 5% at 9 years, all at P < .001. Having ≥25% of food left uneaten (51.2% of participants) had no relationship to survival at all follow-up durations. At 9 years, compared with those with BMI < 18.5kg/m(2), the normal weight (BMI 18.5-22.9 kg/m(2), Asia Pacific cut-off), overweight (BMI 23-25 kg/m(2), Asia Pacific cut-off) and obese (BMI > 25 kg/m(2), Asia Pacific cut-off) had significantly lower mortality (hazard ratio 0.65, 0.62, and 0.47, respectively, all P < .001).

Conclusions: Significant weight loss as defined by the Minimum Data Set was not associated with short- or long-term survival in Chinese nursing home residents. BMI, however, is predictive of short- and long-term survival irrespective of weight loss in this population. Low BMI, detectable at a single point of time, may be another readily available alternative trigger point for possible interventions in reducing mortality risk. Obese residents had the lowest mortality compared with those with normal weight.