Why do we feel older on some days than others?

People who feel young for their age tend to live longer than those who don't. Indeed, it's thought that what psychologists call "subjective age" is likely a pretty accurate marker for a person's actual psychological and physical health. While a lot of past research has looked at the major factors that influence changes in subjective age over a lifetime, such as chronic physical disease and mental health problems, a new study published recently in Psychology and Health has investigated the day-to-day fluctuations in how old older people feel.

Dana Kotter-Grühn and her colleagues recruited from community activity groups 43 adults aged 60 to 96 (39 women; average age 75) and asked them to keep a detailed diary for eight days. None of the participants were cognitively impaired. Toward the end of each day, the participants stated in years how old they felt that day, and they answered questions about the moods they'd experienced, any physical symptoms they'd experienced including any pain, and any daily stressors, such as having an argument with someone.

Overall, these chirpy participants mostly tended to feel substantially younger than their actual age, by between 12 and 15 years on average. However, for most participants, their subjective age fluctuated from one day to another, and these variations correlated with most of the other measures taken.

On average, people felt subjectively older on days that they experienced more bad moods, and/or stressors and/or more physical symptoms. Subjective age was most strongly associated with the scores for bad moods and stressors, and was less strongly associated with the scores for physical symptoms and pain (and unlike negative moods, positive moods were not correlated with subjective age).

To take a couple of examples, on a day with a lot of bad moods, participants averaged feeling 12.57 years younger than they really were, compared with 14.93 years younger on days with few bad moods. Meanwhile, on a day with more pain than usual, felt age was 13.12 years less than actual age, compared with 14.7 years less than actual age on days with less pain than usual.

The researchers also looked to see if lower or higher subjective age on one day was followed by changes in moods, stressors and physical symptoms on the following day, or vice versa, to try to find out if bad days make us feel older over time, or if feeling older one day leads us to have a bad day the next.

However, they found no evidence for these day-to-day effects either way. This could be because of weaknesses in the study design, such as having too few participants, or only one diary entry point per day, or it could suggest that some other factor or factors not measured here have a deeper causal role, affecting people's felt age and their mood and physical state.

The researchers said theirs is one of the first ever studies to investigate how subjective age varies on a daily basis. "Our finding that the number of daily stressors is coupled with daily felt age discrepancy can be understood in the context of stress being a major 'ager'," they said.

"Together these results provide support to a conceptualisation of the age individuals feel on a daily basis as a marker of individuals' physical and mental health. Thus simply asking a person how he/she feels may yield insights into the physical and mental state of the person and his/her experience of getting older."