I’m a subscriber to New Scientist, the British weekly magazine of science news for the rest of us. I subscribed to Science for a while too, because it publishes researchers’ actual articles, but decided I’d rather have more numerous reports with less math. New Scientist contains short reports and a few longer articles as well as interviews, and a great feature at the end where people write in requesting explanations for odd observations (very British, I think, in the tradition of the journal Notes and Queries (1849 – present), or letters to the London Times from country parsons reporting the first sighting of a bird).

Anyway, though I still find NS interesting and valuable, I’ve begun to feel they are sometimes sacrificing science for snappy headlines. Here’s an example that is from a while ago, but quite illustrative.

Housework helps combat anxiety and depression

FEELING down? You might be able to dust away your distress. Just 20 minutes a week with the vacuum cleaner or mop is enough to help banish those blues, and sport works even better.
That’s the message from Mark Hamer and his colleagues at University College London, who wanted to find out what benefits arise from different types of physical activity. They examined data from questionnaires filled in by almost 20,000 Scottish people as part of the Scottish Health Surveys, carried out every few years. Some 3200 respondents reported suffering from anxiety or depression, but those who regularly wielded the mop or the tennis racket were least likely to suffer, the researchers report (British Journal of Sports Medicine, DOI: 10.1136/bjsm.2008.046243).

One 20-minute session of housework or walking reduced the risk of depression by up to 20 per cent. A sporting session worked better, reducing risk by a third or more. Failing housework or sport, says Hamer, try to find something physical to do. “Something – even for just 20 minutes a week – is better than nothing.”

––From issue 2652 of New Scientist magazine, 19 April 2008, page 4-5. Abstract of original available free, entire article requires fee to BJSM.

Why we shouldn’t believe this

In New Scientist’s brief bit, there’s absolutely no evidence for a causal relationship between exercising and being less depressed. It’s an example of the frequent, but quite false, assumption that because two things are associated, one causes the other. Other relationships are quite possible. Does physical activity really reduce depression and anxiety, or are the people who actually do housework or sports simply the ones who have less severe symptoms to start with? Or is there some other connexion altogether? Nothing in the New Scientist, or the article abstract, addresses that question. But it makes an eye-catching headline, to say that housework cures depression.

To investigate the question scientifically, it is necessary to take a large number of depressed people and randomly assign them to one of three groups: an exercise group, a control group given some other task like filling in a weekly questionnaire or reading about depression, and a third group who don’t get any new activity or other attention from the researchers. (Ideally those doing the testing and analysis don’t know which group is which.) Then, at the beginning and end of the study, measure psychological state using some accepted reliable tests and see what changes. Finally, use statistical analysis to see if the changes are significant or might be due to chance. [Even after that, other factors may make the apparent conclusions false: maybe the exercise was not enough to have an effect, or during the study the country went to war and everybody stayed depressed, or the social aspects of being in an exercise group had more effect than the actual jumping and sweating did.]

No doubt such a study has been done, probably more than once; advising depressed people to get more exercise is a standard approach and insurance companies would love to fund the research to support it. Mark Hamer might have cited previous work in the full text of his article in the British Journal of Sports Medicine (which New Scientist should have read before writing their brief and provocative piece) but we readers have no way of knowing this.

In this particular case––the effect of exercise on individuals––researchers would have to be vigilant about the distortion of results due to participants dropping out or failing to comply with the activity levels. Even the method of choosing participants can affect reliability of results: if the depressed people are chosen from those who show up at clinics, their symptoms may be overall less severe than the symptoms of people too depressed even to go to a clinic.

A similar example: exercise and fibromyalgia

I have fibromyalgia, and some researchers have pronounced aerobic exercise to be beneficial for reducing the symptoms of this condition’s chronic pain and fatigue. Exercise is fundamentally a good thing, I agree. It distracts one from symptoms, adds an interest, may confer a feeling of control over one’s illness, strengthens muscles, promotes growth of new neurons in the brain, and can improve flexibility.

But. In moderate to severe cases of fibromyalgia, even mild exertion can cause greatly increased pain and exhaustion. Unlike the familiar “weekend athlete” reaction, the increased pain and fatigue may last a week or several weeks. This means that for some individuals the goal of walking briskly for a few blocks could take years to attain, since we are knocked back to the starting point when we overdo, or when something else in our lives like a cold or interrupted sleep aggravates our symptoms.

Some time ago I read a review article which gathered the results of a number of studies on exercise and fibromyalgia, and I noted that in some the dropout rate was high but wasn’t mentioned in interpreting the data. And then there are people, like myself, who would never enroll in an aerobic exercise program because we’ve “been there, done that” and it was painful and unproductive. If we’re not counted, and a high dropout rate is glossed over, then to whom do the results apply?

What can we say about exercise, then?

I am skeptical of the efficacy of exercise as a general one-size-fits-all prescription for fibromyalgia or depression. I would suggest the fibromyalgia studies really show that exercise appears to be helpful for those people able to endure it, but, while all patients should be encouraged to do appropriate activities as tolerated, there’s a need to be gradual and cautious. Some patients may never be able to attain exercise levels that make appreciable improvements to their symptoms, despite sincere efforts. (This doesn’t mean that exercise is without benefits to them, though. My level of physical activity doesn’t seem to help my pain, fatigue, or quality of sleep, but I’m much happier when I get out for a walk or a bit of gardening.) At an education class on fibromyalgia, I heard someone ask “How can I exercise when even walking around the house is too strenuous?” The reply was, “Can you get up and walk all the way around your kitchen table? Good. Start with that and work up.” Sensible advice, but actual improvement in symptoms may be a very long time in coming for that person.

For depressed people, exercise is unlikely to be harmful and may indeed help––I myself believe that it does––but there’s no evidence of that in the New Scientist account of Mark Hamer’s work.

I felt this was worth writing about for two reasons, one general and one particular. It’s a good example of how the media gives us accounts of scientific research without the details needed to evaluate them. And, invisible conditions like fibromyalgia and depression are different from most other health problems. They are regarded by many as non-ailments or personal weakness/malingering, so it is easy for “exercise may help” to become “quit complaining, pull up your socks and get on with it”. From there it’s a short step to “all these patients could feel better but they just won’t do the work necessary; they cling to their disease.”

And I have to admit that the example used, housework, was particularly galling to me. While there are people who can enjoy housework as a zen activity, or feel great satisfaction at making their floors and sinks shine, most of us (male or female) do not get much pleasure at all from it. Every time you do it, next day there it is again, dirty dishes, laundry piling up, dog hair floating across the floor. Truly, housework is never done. And, given that housework is still seen more as a woman’s responsibility than a man’s, and that women have a higher rate of depression than men, the “FEELING down? You might be able to dust away your distress” line seems offensively sexist and dismissive.