Hen or egg? Repeated longitudinal analysis of the relationship between depressed mood and bADL dependency in the Longitudinal Urban Cohort Ageing Study (LUCAS) from 2007–2017

Introduction: Disturbed cognitive function may influence physical function and vice versa. In LUCAS, comprehensive functional and psychosocial data were gathered from each cohort member at 6 waves in 2-year intervals between 2007 and 2017. Our research question concerned the temporal relation between depressed mood (DM) and basic activities of daily living (bADL). Methods: LUCAS comprised n = 2012 persons in 2007, mean age 76.2 years, 63.1% women; in 2017 n = 776, mean age 82.8 years, 61.9% women. DM was defined ‘‘During the last month, have you felt so down in the dumps that nothing could cheer you up?’’ (yes); bADL dependency ‘‘Do you need help from someone else with any of the following? (a) feeding yourself (b) getting to the toilet (c) dressing yourself (d) bathing yourself (e) moving from bed to chair or standing up’’ (yes). Using data from two successive waves, we did two tabu- lations per wave-pair: eg. (1) DM from 2007 vs. new bADL from 2009, (2) bADL from 2007 vs. newDM in 2009; similarly for the other 4 wave-pairs between 2009 and 2017. Results: Twenty-five of 1321 (1.9%) non-depressed and 8/145 (5.5%) depressed persons in 2007 had developed bADL-dependency by wave 2009 (OR 3.03; Fisher p = 0.012). Age-sex-adjusted: OR 3.09; 95%; c.i. 1.343–7.126, LR p = 0.008). Conversely, 62/1314 (4.7%) in 2007 bADL-independent and 3/37 (8.1%) bADL-dependent persons had developed DM by wave 2009 (OR 1.78, Fisher p = 0.419). After adjustment: OR 1.76; 95%; c.i. 0.507–6.090, p = 0.374. Analyses for the remaining 4 wave-pairs showed the same pattern. Key conclusions: Depressive mood at wave 9 increases the risk of new bADL-dependency at wave x ? 1. Conversely, bADL-depen- dency at wave 9 does not significantly increase the risk of new depression at wave x + 1.

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