Olfaction and Physical Functioning in Older Adults: A Longitudinal Study

Poor olfaction is associated with worse functional performance in older adults, but longitudinal evidence is lacking. We investigated poor olfaction in relation to longitudinal changes in physical functioning among community-dwelling older adults.

The analysis included 2 319 participants from the Health, Aging and Body Composition study (aged 71-82 years, 47.9% men, and 37.3% Blacks) who completed the Brief Smell Identification Test in 1999-2000. Olfaction was defined as good (test score 11-12), moderate (9-10), or poor (0-8). Physical functioning was assessed up to 4 times over 8 years, using the Short Physical Performance Battery (SPPB) and the Health Aging and Body Composition Physical Performance Battery (HABCPPB). We conducted joint model analyses and reported the differences in annual declines across olfaction groups.

During the follow-up, compared to those with good olfaction, older adults with poor olfaction had greater annual declines in both the SPPB score (-0.137, 95% CI: -0.186, -0.088) and all its subscales: standing balance (-0.068, 95% CI: -0.091, -0.044), chair stand (-0.046, 95% CI: -0.070, -0.022), and gait speed (-0.022, 95% CI: -0.042, -0.001). A similar observation was made for the HABCPPB score (difference in annual decline: -0.032, 95% CI: -0.042, -0.021). These findings are robust and cannot be explained by measured confounding from demographics, lifestyle factors, and chronic diseases or by potential biases due to death and loss of follow-up. Similar associations were observed across subgroups of sex, race, and self-reported general health status.

This study provides the first epidemiological evidence that poor olfaction predicts a faster decline in physical functioning. Future studies should investigate potential mechanisms.