OBJECTIVES: the 'triad of impairment' phenomenon describes the co-occurrence of age-related cognitive, emotional and physical functioning deficits. We investigated how occupational profile and childhood intelligence contribute to the triad of impairment in late life.
METHODS: we analysed data of a subsample of the Aberdeen Birth Cohort of 1936 (n= 346). Data were collected on participants' childhood intelligence, late-life cognitive ability, physical functioning, depressive symptoms and main lifetime occupation. We summarised the various occupational and impairment measures into two latent variables, 'occupational profile' and the 'triad of impairment'. We used a series of data reduction approaches and structural equation models (SEMs) of increasing complexity to test both the validity of the models and to understand causal relationships between the life-course risks for the triad of impairment.
RESULTS: occupational profile had a significant effect on the triad of impairment independent of childhood intelligence. Childhood intelligence was the predominant influence on the triad of impairment and exerted its effect directly and indirectly via its influence on occupation. The direct effect of childhood intelligence exceeded the independent influence of the occupational profile on impairment by a factor of 1.7-1.8 and was greater by a factor of ∼4 from the indirect pathway (via occupation).
CONCLUSIONS: childhood intelligence was the predominant influence on the triad of impairment in late life, independently of the occupational profile. Efforts to reduce impairment in older adults should be informed by a life-course approach with special attention to the early-life environment.
The authors thank members of the Aberdeen 1936 Birth Cohort for their contributions to this project.
This work was supported by the PhD studentship Pathways to a Healthy Life, University of Aberdeen (2013–2016), and Pump Priming Grant, University of Aberdeen (2013). The Aberdeen 1936 Birth Cohort studies were supported by
Biotechnology and Biological Sciences Research Council (1999–2002); Scottish Health Department (2000–2001); Wellcome Trust (2001–2006); Medical Research Council (2002–2003); Alzheimer Research UK (2003–2006); Alzheimer Society (2006–2008) and University of Aberdeen Development Trust (2006–2009) contributions. C.B. was supported by The Farr Institute @ Scotland. The Farr
Institute @ Scotland is supported by a 10-funder consortium: Arthritis Research UK, the British Heart Foundation, Cancer Research UK, the Economic and Social Research Council, the Engineering and Physical Sciences Research Council, the Medical Research Council, the National Institute of Health Research, the National Institute for Social Care and Health Research (Welsh Assembly Government) and the Chief Scientist Office (Scottish Government Health Directorates), the Wellcome Trust, (MRC Grant No: MR/ K007017/1).
- childhood IQ
- cognitive impairment
- physical functioning
- depressive symptoms
- older people