Researchers from Erasmus University, The Netherlands, and Monash University, Australia, say theirs is the first study to determine the independent association of various measures of subjective health with mortality. Previously, few studies had showed an effect of physical functioning independent of other subjective measures.
The researchers evaluated data on 5,538 adults who took part in the Rotterdam Study and who were followed for a mean of 12 years. One-third had cardiovascular disease; 8% had chronic obstructive pulmonary disease, and 38% had joint problems.
The researchers investigated 6 different measures of subjective health and how they related to all-cause mortality. They conceptualized subjective health—often associated with health and well-being—as a continuum with physical functioning at one end and mental health at the other. Physical functioning included basic activities of daily living (BADL), such as eating and grooming. Instrumental activities of daily living (IADL) included the cognitive attributes of performing self-reliant daily tasks, such as meal preparation and shopping. The researchers assessed mental health with scales measuring positive and negative effects as well as somatic symptoms (the physical manifestations of dysthymia) and quality of life.
“Importantly,” the researchers say, any of those indicators is affected strongly by both physical and mental aspects of health. For example, physical and functional decline are related to higher scores on dysthymia questionnaires.
During 48,534 person-years of follow-up, 2,021 people died. Only impairment in physical functioning assessed by either self-report of BADL or IADL was related to mortality. Quality of life, positive affect, somatic symptoms, and negative affect did not predict mortality once self-rated physical functioning was accounted for.
Clinically speaking, the researchers say, it might be good to focus interventions aimed at improving survival on subjective indicators of physical well-being: in other words, activities of daily living and what it takes to perform them.