Associations of cold spells and heat waves with frailty trajectory among older adults: a longitudinal study from the JAGES Study

OBJECTIVES: The impact of extreme weather on frailty trajectories in older adults remains unclear. This study explored the associations between cold spells/heat waves and frailty trajectories among this population. METHODS: A total of 6582 older adults who completed four survey waves of the Japan Gerontological Evaluation Study in 2010, 2013, 2016 and 2019 were included. Frailty was assessed using the Kihon Checklist, and frailty trajectories were identified using group-based trajectory models. The cumulative number of days participants were exposed to cold spells and heat waves was calculated. Multinomial logistic regression models were applied to examine associations between extreme temperature exposure and frailty trajectories, with adjusted ORs and 95% CIs estimated. RESULTS: Three frailty trajectories were extracted and labelled as frailty worsening, frailty maintenance and frailty improvement. Of the 6582 participants, 20.8%, 49.8% and 29.4% were subsequently classified into the above three trajectories. Every 1-day increment of cold spell that participants suffered was associated with 5.4% (95% CI 1.040 to 1.067) increased risk of frailty worsening after adjustment for covariables; similarly, for each additional day of heat wave participants were exposed to, the risk of frailty maintenance and frailty worsening raised by 1.6% (95% CI 1.004 to 1.028) and 4.5% (95% CI 1.032 to 1.058), respectively. CONCLUSIONS: Cold spells and heat waves are linked to higher frailty worsening risk in older adults, emphasising the need for targeted public health interventions.