Abstract
Background:
There is limited data on predictors of long-term functional status in population samples, and even less about the effect of vascular risk factors on function. We hypothesized that functional status would decline over time, and that vascular risk factors would affect function and mediate functional decline.
Methods:
The Northern Manhattan Study contains a prospective, population-based study of 3298 stroke-free individuals
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40 years of age, followed for a median of 11 years for vascular events. The Barthel index (BI) was assessed annually and analyzed as a continuous variable on a 100-point scale. Generalized estimating equations models were adjusted for demographic, medical, and social risk factors assessed at baseline. Models were censored and uncensored for stroke and myocardial infarction (MI) occurring during follow-up. Secondarily, motor and non-motor domains of the BI were analyzed separately, and models were stratified by age.
Results:
Mean age (standard deviation) was 69.2 (10) years, 37% were male, 52% Hispanic, 22% had diabetes, and 74% hypertension. Among 3298 participants, there were 33556 BI assessments. There was an annual decline of 1.02 BI points (p<0.0001). Predictors of change in BI over time included: age (−0.08 BI points per year; p<0.0001), Hispanic ethnicity (−0.22 per year, compared to white; p=0.016), female sex (−0.30 per year, compared to male; p<0.0001), diabetes (−0.38 per year, compared to non-diabetics; p=0.0002), and depression (−0.26 per year, compared to no depression; p=0.046). Results did not change when stroke and MI were censored. Magnitude and significance of predictors of BI were similar for motor and non-motor domains. The following had a different effect on change in BI in those above the median age (68 years), compared to those less than or equal to the median: age (−0.15 per year vs. −0.03; p for difference <0.0001), female compared to male sex (−0.43 per year vs. −0.15; p=0.049), and depression compared to no depression (−0.64 per year vs. −0.008, p=0.023).
Conclusion:
In this large, population-based, multi-ethnic study with long-term follow-up, we found a 1% mean decline in function per year that did not change when the effect of vascular events was excluded by censoring. Vascular risk factors predicted functional decline even in the absence of clinical events. The impact of gender sex and depression was stronger amongst the elderly.