Does age modify the relationship between morbidity severity and physical health in English and Dutch family practice populations?

To investigate the co-influences of age and morbidity severity on physical health in adult family practice populations. Morbidity data in a 12-month period for 7,833 older English consulters aged 50 years and over and 6,846 Dutch consulters aged 18 years and over was linked to their physical health status obtained from cross-sectional health surveys. Individual patients were categorised using 78 consulting morbidities classified by a chronicity measure (acute, acute-on-chronic and chronic) into an ordinal scale of morbidity severity ranging from single to multiple chronicity groups. Associations between morbidity severity, age and SF-12 Physical Component Summary (PCS) score were assessed using linear regression methods. Increased age and higher morbidity severity were significantly associated with poorer physical health. Of the explained total variance in adjusted PCS scores, an estimated 43% was attributed to increasing age, 40% to morbidity severity and 17% to deprivation for English consulters; the figures were 21, 42 and 31%, respectively for Dutch consulters. The largest differences in PCS scores between severity categories were observed in the younger age groups. Morbidity severity and age mainly act separately in adversely influencing physical health. In ageing populations who will experience higher multimorbidity, this study underlines the importance that health care and public health will need to address morbidity severity and ageing as related but distinct issues.