Table gives the background characteristics of the women at recruitment. The mean age at recruitment was 55 years (SD 2.5), most were married or cohabiting, were well educated, and were urban dwellers. The two age-groups were very similar by the studied background characteristics.
Description of the women at recruitment, %
Table gives the prevalence of vasomotor symptoms according to a cross-sectional analysis. At the time of recruitment, about two thirds of the women reported vasomotor symptoms, and about a half regarded them as bothersome. In the survey a year later, less (53%) of women reported vasomotor symptoms and a third found them bothersome. In the surveys 2–4 years later, the proportions reporting symptoms were lower (around 40%), while a fourth of the women reported them being bothersome. The prevalence of women reporting bothersome symptoms declined by 29% from recruitment to the 1-year follow-up and by 41% to the 2-year follow-up. Thereafter the prevalence of symptoms remained at roughly the same level.
Proportions (%) of women with vasomotor symptoms and bothersome symptoms1 in past two weeks, at each survey (cross-sectional analysis)
Table gives the results of the longitudinal analysis in which the same women were followed from one survey to another. There were some differences by the number of follow-ups (how early or late the woman was recruited) as well as by compliance with the surveys (did she skip some of the surveys, group “Intermittent surveys” in Table ). In the groups with only three or two measurements or intermittently, the proportion declined over time. In the group having most follow-ups, the proportion of women with bothersome symptoms first increased and then decreased. In the group with three follow-ups, the proportion first declined, and then stayed about the same. Some women had symptoms variably (i.e. having one or more measurements without symptoms and then again reporting symptoms). Younger women did not systematically have more bothersome symptoms than older women.
Proportions (%) of women with bothersome vasomotor symptoms in past two weeks over time, by the number of follow-ups women had (longitudinal analysis)
Comparing the proportions of women with bothersome symptoms at various times to those in the cross-sectional analysis of Table reveals relatively similar percentages.
For comparison, we also studied psychological symptoms (depression and/or irritability) and pains (head, back and/or joint pains; stomach) in the cross-sectional analysis (Data not shown). The prevalence of bothersome psychological symptoms (depression or irritability) declined notably (by about half) from recruitment to the 3-year follow-up, but there was very little change in the prevalence of women reporting bothersome pains.
About two thirds of the women in this selected group of women reported vasomotor symptoms and about half reported them being bothersome symptoms. There was a notable variation in the development over time in the prevalence of bothersome symptoms. The development over time was related both to the timing of entering the study, and the compliance with answering the surveys. Our sample size was too small to analyze this in relation to background characteristics to explain the variation.
The results of the longitudinal analysis (comparing the same women over time) and those of the cross-sectional analysis showed relatively similar results. Thus, we can interpret the cross-sectional data as generally summing up the experience of all women throughout the follow-up, even though different women answered in different surveys.
We had originally planned to make a longitudinal analysis using time-to-event calculations (event being the end of symptoms) and estimate the duration of vasomotor symptoms. However, we did not have reliable data of the duration of symptoms before recruitment and complete measurements were not available for all women. Furthermore the numbers of women in early menopause were few.
These complications of data led us to the crude analysis used in the study. However, our analysis was good enough to show the variability between women, and suggest the need for larger follow-up studies to describe the natural course of menopausal symptoms. To estimate the duration of symptoms among unselected women and to estimate the burden of symptoms related to menopause, one would need a follow-up since menopause in a population not using hormone therapy.
Our study women are not a representative sample of women, but women who were motivated to join a preventive drug trial. A comparison of women wanting and not wanting to join the trial showed that the studied menopausal symptoms were four times more common among those who initially expressed an interest than among those who were not interested at the time of asking [25
]. Thus, at a population level, the prevalence of symptoms is much lower, but we know nothing of whether the disturbance and variability among those who have symptoms is the same as in our trial.
For comparison, we studied bothersome psychological symptoms and pains in the cross-sectional analysis. The psychological symptoms were less common, but otherwise behaved as vasomotor symptoms; there was very little change in the prevalence of women reporting bothersome pains. If a longitudinal study on menopausal women were to be made, other non-menopausal symptoms should also be studied.
As the overall balance of effects of postmenopausal hormone therapy (HT) on chronic diseases is not positive (at the population level) [26
] the use of HT is argued largely on the basis of symptom relief. As the current knowledge of the frequency or level of disturbance of symptoms is patchy [14
], population-based follow-ups on the natural course of menopausal symptoms are clearly needed. Even though such averaged information does not accurately predict the fate of individual women, it would be useful for women when they are trying to decide whether or not to use HT. In the past such research was difficult as HT was very commonly used. With the current knowledge on the mixed effect on diseases, it might be feasible to find a representative cohort of new menopausal women without HT for follow-up studies.