This study is the first to explore how daily life experiences of sleep, mood and pain relate to appetite using experience sampling methodology in a cohort of community dwelling older adults aged 75 years and older. Males reported a poor appetite on 12% of the measured days and females on 19% of the days. We found that those with lower mood or poorer sleep, and males with more severe pain, have a poorer appetite compared to those with higher mood, better sleep, or less pain. Additionally, a decrease in mood, deterioration of last night's sleep, or an increase in pain (males only) are associated with a decrease in appetite on the same day. Sex differences were observed, with mood being more strongly associated with appetite in females and pain being only observed in males.
Of all factors, depressive symptoms have been most often studied and linked to a poorer appetite in older adults in cross-sectional studies (10, 12, 14, 20, 21). In our study, among the three factors examined, mood showed the strongest association with a poor appetite. It is important to clarify that a single question about experienced mood is not equivalent to a full assessment of depressive symptoms. However, a cross-sectional study among 292 older adults (≥ 60 years) attending senior centres or living in assisted living facilities found that a single-item question about mood was even more strongly correlated with a poor appetite than using the 5-item Geriatric Depression Scale to assess depressive symptoms (20). The association between mood and appetite may be explained by the effect of mood on taste and smell reduction (37), induction of anhedonia (38), or reduction of executive functioning associated with fatigue (39), subsequently lowering appetite. Though reduced taste and smell may remain stable from day-to-day, the latter two pathways might explain within-subject associations. We also found that the mood-appetite association is stronger in older females than in older males. Prior studies did not stratify by sex, so comparisons are limited. A recent qualitative study among older adults revealed that mood significantly influences the emotional experience of appetite and that older females often discussed various mood states related to poor appetite, while older males related their poor appetite experiences to clinical depression or stress (40). If confirmed by other studies, our findings suggest that older females may be more vulnerable to mood's impact on appetite than older males.
Our study aligns with previous cross-sectional research, which suggests a link between sleep problems and poor appetite in older adults, even when adjusting for depressive symptoms (22, 23). However, one study found a positive association that lost statistical significance after accounting for various confounding factors (10), likely due to lower statistical power compared to our study. Furthermore, recent studies have linked poor sleep quality or shorter sleep duration with malnutrition (41–46), possibly mediated by poor appetite. Several hypotheses can be proposed to explain the underlying mechanism. One is that between-subject associations may be attributed to lower expression of the neuropeptide orexin with aging in some individuals, leading to both reduced appetite and lower daytime arousal (47, 48). Consequently, increased daytime napping could negatively impact nocturnal sleep (49). However, this explanation is less likely to explain the day-to-day within-subject associations. Another possibility is that poor appetite leads to inadequate nutritional intake, which in turn results in poorer sleep due to reduced levels of sleep-inducing hormones like serotonin and melatonin, both derived from tryptophan. However, the most plausible explanation appears to be that poor sleep causes fatigue the following day, subsequently reducing appetite. Regarding the presence of sex differences, our study did not uncover strong evidence supporting their existence.
We identified only two prior cross-sectional studies that examined the association between (chronic) pain and appetite in older adults (10, 19). In one of these studies, an initial univariable analysis revealed an association between the presence of pain and poor appetite. However, this association lost statistical significance after adjusting for a broad range of confounding factors (10). In the other study, which focused on 65 older adults with non-malignant pain (75% females), it was found that those reporting poorer appetite also reported higher pain intensity (19). However, no statistical adjustments were made for other factors. The link between pain and reduced appetite might be explained by a neural mechanism. Studies conducted on rats suggest that specific hypothalamic neurons, responsible for suppressing appetite in response to metabolic cues, may also play a role in reducing food intake in response to pain signals (50). Notably, while reports of pain are consistently higher in we observed associations between pain and appetite in older males, both between subjects and within subjects, but not in older females. This could be due to to sex differences in e.g. pain perception or psychological and emotional responses to pain that impact appetite regulation. However, further research is required to validate these findings.
This study is the first to explore appetite associations by using experience sampling methodology and systematically considering potential sex differences. Our study design not only reaffirmed the associations between factors previously linked to poor appetite in cross-sectional studies at the between-subject level, accounting for confounding factors, but also identified daily within-individual associations. Furthermore, in addition to the more established association between mood and appetite, our study also shed light on the less-explored association between sleep and pain with appetite.
The study's strengths include a large sample of older adults from a population-based study and the use of multiple week diaries, which increased study power, enabling detection of small associations. However, limitations should be acknowledged. Participants were somewhat healthier and higher educated, potentially underestimating associations due to lower prevalence of poorer appetite and other experienced problems, reducing measure variance. Additionally, existing data limited the inclusion of all potential time-varying factors. Future studies with similar methodology could consider factors like physical activity and sedentary behaviour that may vary from day-to-day. Moreover, within and between-person associations might be influenced by unknown (confounding) factors, such as hormonal fluctuations or unaccounted external factors like the time of day when participants completed their diaries. Lastly, measurements were conducted only once a day while the experiences of pain, mood, sleep, and appetite may also fluctuate throughout the day.
The results of this study suggest that poor sleep, lower mood (more strongly in females) and more severe pain (males only) are associated with poorer appetite in older adults on a daily level both within and between persons. As a poor appetite is an important risk factor for the development of malnutrition (2–4), frailty (5) and mortality (6), interventions targeting these underlying factors could prevent or postpone these adverse outcomes. In addition, clinicians should be aware that a poor appetite can signal the presence of other underlying issues such as low mood, poor sleep, or pain, all of which have a substantial impact on an individual's quality of life and necessitate attention. Additionally, the observed sex differences suggest that factors linked to poor appetite may vary based on sex. This highlights the importance of considering sex differences in both future research and, if confirmed by other studies, clinical practice. Such an approach can lead to more tailored and effective interventions to address appetite-related concerns among older adults.