Association of multimorbidity and mortality interacting with pulmonary function: a prospective cohort from NHANES

<bold>Purpose:</bold> This study aimed to investigate how pulmonary function impacts mortality in individuals with multimorbidity. <bold>Material and Methods:</bold> This study used US NHANES data from 2007-2012 to examine the relationship between multimorbidity, pulmonary function, and mortality. Multimorbidity was measured by counting diseases, and FEV1 and FVC were used to assess pulmonary function. Cox proportional hazards model and restricted cubic spline were used to analyze the associations between multimorbidity and all-cause mortality, as well as major cause mortality such as cardiovascular disease (CVD) and cancer. We used a stratified analysis and a joint analysis to test how pulmonary function and multimorbidity interact to identify individuals at higher risk of mortality. <bold>Results:</bold> During a mean follow-up of 9.74 person-years, 1029 deaths were observed, with 221 attributed to CVD and 305 to cancer. Adults with multimorbidity had higher risks of all-cause mortality, CVD mortality, and cancer mortality compared to those without multimorbidity. Pulmonary function mediated 14% and 11% of these risks for FEV1 and FVC, respectively. The association between multimorbidity and all-cause mortality was stronger in individuals with low pulmonary function. Adults with reduced lung function and multiple diseases have a higher risk of all-cause mortality compared to those with normal lung function and fewer diseases. <bold>Conclusion:</bold> Improving pulmonary function may not significantly reduce health inequities related to multimorbidity in the US. However, maintaining normal pulmonary function can lower mortality rates in various health conditions.