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Coffee consumption, RF, and the risk of RA
  1. J H GLASER
  1. 4 Woodpark Circle
  2. Lexington, MA 02421, USA
  3. Glaserj{at}polaroid.com
    1. M HELIÖVAARA,
    2. K AHO,
    3. P KNEKT,
    4. A REUNANEN,
    5. A AROMAA
    1. National Public Health Institute
    2. Helsinki, Finland
    3. Social Insurance Institution
    4. Research and Development Centre
    5. Turku, Finland
    1. Dr M Heliövaara, National Public Health Institute, Mannerheimintie 166, FIN-00300 Helsinki, Finland markku.heliovaara{at}ktl.fi
    1. O IMPIVAARA
    1. National Public Health Institute
    2. Helsinki, Finland
    3. Social Insurance Institution
    4. Research and Development Centre
    5. Turku, Finland
    1. Dr M Heliövaara, National Public Health Institute, Mannerheimintie 166, FIN-00300 Helsinki, Finland markku.heliovaara{at}ktl.fi

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    Stress is one of the factors that can trigger the onset of rheumatoid arthritis (RA). People working under deadline pressure, and people characterised as hard driving, “type A” personalities may be most likely to experience stress. These are the same people who may consume large quantities of coffee in order to stay at peak performance for longer periods of time. Possibly, therefore, the correlation reported by Heliövaara et al 1between coffee consumption and RA may, in part, be due to the association between stress and RA.

    References

    Authors' reply

    The plausible hypothesis presented by Dr Glaser prompted us to complement our earlier results with a further analysis of data from the Finnish surveys.

    Using information derived from the Mini-Finland Health Survey,1-1 we studied stress and type A behaviour pattern for their associations with coffee consumption and the occurrence of rheumatoid factor (RF). In this survey we asked the participants about having been exposed to hurried or tight work schedules in their current occupation and in the previous occupation of longest duration. The Jenkins Activity Survey AB scale scores were computed from a standard questionnaire.1-2 1-3

    Contrary to the hypothesis, there was a negative association between hurried or tight work schedules and the occurrence of RF (table 1-1). No significant association was seen between type A behaviour and RF. Coffee consumption showed only weak associations with work hurries (r=0.035, p=0.004) or the AB scale score (r=0.001, p=0.54).

    Table 1-1

    Age and sex adjusted odds ratio (with 95% confidence interval (CI)) of rheumatoid factor (RF) positivity (sensitised sheep cell agglutination titre 128) for hurried or tight work schedules and for the type A behaviour pattern among participants without clinical arthritis in the Mini-Finland Health Survey

    We also studied a set of five stress related symptoms for their prediction of RF positive rheumatoid arthritis (RA) in the Mobile Clinic Health Examination Survey.1-4 In the baseline questionnaire, the subjects were asked: Have you lately suffered from nervousness? ...continuous fatigue? ...excessive sweating? ...heart pounding? ...continuous headache? Similar self reported complaints in a standard symptom inventory are likely to reflect anxiety, depression, and somatisation.1-5

    No positive association was found between stress symptoms and RA risk, and again, contrary to the hypothesis, there was a negative association between excessive sweating and future RA (table 1-2). This unexpected finding may be due to either some unknown factor or to chance alone. It is not known whether there are joint determinants for sweating and RA, such as changes in sex hormones, or whether early Sjögren's syndrome might precede the onset of arthritis in the long term.

    Table 1-2

    Relative risk2-1-150 (with 95% confidence interval (CI)) of developing rheumatoid factor positive rheumatoid arthritis for different stress symptoms among 52 260 participants of the Mobile Clinic Health Examination Survey

    These results do not support the contention that the associations between coffee consumption and RF and RA are attributable to stress. However, we have no survey data on stressful life events that in particular have been supposed to act as a precipitating factor for RA.1-6 Moreover, many determinants of RA presumably are still unknown. Both the letter by Dr Glaser and the results of our complementary analyses indicate the need for advanced epidemiological studies.

    References

    1. 1-1.
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    4. 1-4.
    5. 1-5.
    6. 1-6.
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