Development of a modified BODE index as a mortality risk measure among older adults with and without chronic obstructive pulmonary disease

Abstract

The BODE index was developed as a prognostic mortality risk tool for persons with chronic obstructive pulmonary disease (COPD). It incorporates 4 measures: body mass index, lung obstruction, dyspnea, and exercise capacity. The intent of this study was to examine how well a BODE-like index constructed using a simpler lung function measure, peak expiratory flow, in combination with physical functioning and symptom information more readily found in survey data (a quasi-BODE index), performs in identifying persons at higher risk of mortality and whether it may be extended as an assessment of mortality risk to persons without diagnosed COPD. Using US national survey data from the Health Retirement Study for 2006-2010, each unit increase in the quasi-BODE index score was associated with a multiplicative 50% increase in mortality risk (odds ratio = 1.50, 95% confidence interval: 1.41, 1.59). The quasi-BODE index is a multidimensional health status instrument based on the BODE index, which is a good predictor of mortality. The quasi-BODE index was compiled using simple measures of physical and respiratory function. It is a potentially useful prognostic instrument for older adult populations with or without COPD, including those with severe physical limitations, particularly when combined with demographic factors and comorbid conditions.

Keywords: chronic disease; dyspnea; frail elderly; health status indicators; lung diseases, obstructive; mortality; respiratory function tests; survival.

Figure 1.

Percentages of respondents over age 50 years (n = 12,501) and aged 65 years or older (n = 8,301) by quasi-BODE index score, Health Retirement Study national surveys, United States, 2006 and 2008.

Figure 2.

Percentages of respondents over age 50 years (n = 12,501) and aged 65 years or older (n = 8,301) within each quasi-BODE index score who died within 2 years postsurvey, Health Retirement Study national surveys, United States, 2006 and 2008.

Figure 3.

Adjusted odds ratio (OR) for risk of mortality within 2 years postsurvey among all respondents over age 50 years (n = 12,501), respondents with chronic obstructive pulmonary disease (COPD) (n = 1,328), and respondents without COPD (n = 11,173), Health Retirement Study national surveys, United States, 2006 and 2008. Odds ratios for a 1-unit increase in quasi-BODE score were estimated separately by group (all respondents, respondents with COPD, and respondents without COPD); odds ratios were also adjusted for sex and age (not shown). Bars, 95% confidence interval (CI).