Fatigue is common among teenage girls and can have a substantial impact on their everyday life, including school attendance and social functioning.
Iron deficiency and anaemia are often considered the most probable explanations for the symptoms of fatigue that teenage girls experience. But our recent findings suggest that the cause is more complicated.
We studied 485 Swedish female high school students. Participants completed questionnaires about fatigue, quality of life, menstrual patterns, diet, nicotine use and dietary supplement use. They also provided blood samples to measure haemoglobin and ferritin – key markers to assess iron status. Low ferritin and low haemoglobin levels typically indicate iron deficiency and anaemia, respectively.
In earlier analyses of the same group, we found iron deficiency was present in 38% of participants. It was strongly associated with both heavy periods (reported by 54% of the participants) and eating a diet with little or no meat (reported by 27% of participants).
In our latest study, the group reported experiencing high levels of fatigue. However, our analyses revealed that neither iron deficiency nor anaemia were associated with higher levels of fatigue or lower quality of life.
In fact, the opposite was true. Lower ferritin and lower haemoglobin levels were linked to less fatigue – even after accounting for confounding factors.
Instead, we found that heavy periods were associated with greater fatigue and poorer quality of life. This was true even after adjusting for ferritin and haemoglobin levels.
This suggests that the association between heavy periods and fatigue is not explained by iron deficiency or anaemia. Other consequences of heavy periods – such as menstrual pain, disturbed sleep or missing school, sports and social activities – may instead contribute.
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Skipping breakfast, lunch or both meals on one or more days per week was also associated with greater fatigue and poorer wellbeing. Daily nicotine use, including snus or smoking, was likewise associated with greater fatigue and poorer wellbeing.
These are important results because heavy periods, skipped meals and nicotine use are modifiable factors that may be overlooked if iron deficiency is assumed to be the only cause of fatigue.
Understanding fatigue
Our study did not capture everything that might influence fatigue. For example, we lacked information on socioeconomic status, physical activity levels, mental health and sleep – factors that may also be related to fatigue.
We also cannot determine cause or effect. For instance, girls may skip breakfast because they’re tired. Nicotine use may be a marker of other lifestyle factors linked to fatigue – rather than a direct cause of fatigue.
Iron deficiency still matters, however. It’s the leading cause of anaemia worldwide. Iron is essential for transporting oxygen to the organs, for good muscle health and normal brain function.
Teenage girls are particularly prone to iron deficiency because their iron needs increase during growth. Menstruation and dietary habits can further reduce iron stores.
Our research will now evaluate a newly developed five-question screening tool for identifying iron deficiency. We will also continue to investigate which symptoms or other indicators are most useful for detecting iron deficiency, and which treatment strategies work best in this population.
These novel results matters because fatigue in teenage girls is often reduced to a question of iron deficiency. Our findings suggest that the picture is more complex. Heavy periods, skipped meals and nicotine use are common and potentially modifiable factors. Overlooking them may mean missing important opportunities to support teenage girls’ health and wellbeing.