Pulmonary function and cognitive decline in an older Chinese population in Singapore

Various cognitive deficits associated with reduced pulmonary function are reported in different studies, but the pattern of cognitive deficits across multiple domains and its associated everyday functional disability remain unclear.

We analyzed neuropsychological functioning, cognitive impairment and accompanying disability in instrumental activities of daily living (IADL) associated with reduced pulmonary function in community-living middle-aged and older adults in Singapore. Performance on a comprehensive battery of neuropsychological tests, spirometry and cognitively demanding IADLs were assessed in the population-based Singapore Longitudinal Ageing Studies.

Consecutive 10% increase in forced expiratory volume in 1 s (FEV1) as percent of predicted was positively associated with 0.18 points increase in Mini-mental state examination (MMSE) and 0.04 points increase in executive function, independent of age, education and other variables. Subjects with moderate-to-severe airway obstruction showed significantly poorer MMSE score (p for linear trend = 0.001), and information processing speed (p for linear trend < 0.001). FEV1 (per 10% of predicted) was significantly associated with lower risk of cognitive impairment (OR = 0.92, 95% CI: 0.87-0.98, P = 0.005) and cognitive IADL disability (OR = 0.86,95% CI:0.79-0.93, P < 0.001). Pulmonary restriction was associated with greater risk of cognitive impairment (OR = 1.98, 95% CI: 1.26-3.11, P = 0.003) and cognitive IADL disability (OR = 2.43, 95% CI: 1.31-4.53, P = 0.005). Moderate-to-severe airway obstruction (OR = 2.04, 95% CI: 1.11-3.74, P = 0.022) was positively associated with cognitive IADL disability.

The findings suggest a measurable but modest cognitive effect of low pulmonary function that was accompanied by corresponding disability in living activities. The effect on executive functioning should be further investigated in longitudinal studies.