The study revealed that the symptoms examined could be grouped into four prevalence patterns. Only five symptoms increased with age, twelve symptoms had stable prevalence, two had a biphasic course (first increasing and then decreasing) and eleven symptoms had decreasing prevalence with age after adjustment for the influence of the final set of covariates on symptom prevalence, thereby making prevalence estimates in various age groups more accurate and comparable.
This study was performed in a random population sample of women aged 35–64 years. The response rate was satisfactory (71%). However, the 29% non-responders may imply a potential selection bias in the estimation of the proportion of women reporting symptom, if responders and non-responder had different characteristics. The distribution of socioeconomic variables and drug use among the responders was similar to that of national samples in Sweden [13, 14]. The size of the potential bias caused by non-response was estimated in a previous publication  and found to be of relatively little importance. Symptom reporting may have been affected by recall bias. However, the recall period of the last 3 months was short and the age range was such that younger and older women may be expected to have similar recall capacity.
The most commonly reported symptoms by the women in this study irrespective of age were general fatigue, headache, irritability, melancholy and backache, occurring in over or around 50% of the subjects. Furthermore, one third or more of the women had symptoms such as insomnia, restlessness, exhaustion and crying easily. Gorman has reviewed gender differences in the epidemiology and clinical presentations of depression . In the United States, 1 out of 5 women suffered from an episode of major depression at some time in her life. Depression was about twice as common among women as among men. Women were more likely to have atypical symptoms of depression such as hypersomnia and hyperphagia, or to have co-morbid anxiety disorders or to attempt suicide than men.
It has previously been shown by Tibblin et al., that there are different symptom prevalence patterns with age . They studied 30 general symptoms in women and men and found generally higher symptom prevalence in women, using the same symptom questionnaire as used in this study. Three symptom patterns were found: increasing, decreasing, and biphasic prevalence, whereas four patterns, increasing, decreasing, biphasic, and stable were seen in the present study. The study by Tibblin et al. was performed some twenty years ago and no adjustments were made to make the age groups more comparable, which might explain the differences found in the two studies .
Five symptoms increased with age. It is a well-established fact  and is part of the normal ageing process, that hearing and vision deteriorate with age. Sleep disturbance has also been found by others to increase with age. It has been shown in a longitudinal study, that sleep duration decreased by 0.4 hours per night for women aged 38–66 years and that sleep problems increased by 30% for women aged 38–84 years [17, 18].
In this study it was seen that leg pain as well as joint pain increased with age. This might partly be explained by increasing weight in those age groups. However, differences in body mass index between the groups were adjusted for, making overweight a less likely cause of these symptoms. Alternately, leg pain and joint pain could be signs of other musculoskeletal disorders, like osteoarthritis or rheumatoid arthritis, both of which have increasing prevalence with age [19, 20].
One third of the symptoms studied had stable prevalence patterns. This is in contrast to prior findings where increasing, decreasing and biphasic courses have been reported . We found stable prevalence patterns for difficulty in relaxing and nervousness, in contrast to the similar symptoms in the decreasing group. However, difficulty in relaxing and nervousness may indicate a personality trait rather than an age-related development. Also, symptoms like coughing, breathlessness and chest pain showed a similar unchanged pattern of relatively low prevalence, ranging from 12.2% to 23.7% among women ages 35 to 39 years indicating a more innocent nature of the symptoms than what it might have been in older age groups.
The prevalence of overweight, constipation, weight loss, and difficulty in urinating were also stable with age. Some of these symptoms, such as poor appetite, weight loss and difficulty in urinating, are commonly associated with serious diseases including diabetes and cancer, while constipation is common among the elderly. In this study overweigh ranged with age from 32.5% to 34.1%. This is broadly in line with what others found .
Two commonly considered groups of symptoms in women during the menopausal transition are psychological and vasomotor symptoms [22–27]. However, many symptoms believed to be related to the menopause also occur before and after this phase . Only two symptoms in our study showed a biphasic pattern, possibly suggesting their association with the menopausal transition. Impaired concentration had a peak, with a maximum prevalence of 32.2% at the ages of 45–49 years, which is in agreement with findings reported by Tibblin et al. . Increased prevalence of sweating was seen between the ages of 40 and 59, which is in line with what others have found [26, 28].
Eleven symptoms had decreasing prevalence patterns with age: general fatigue, headache, irritability, melancholy, backache, exhaustion, feeling cold, crying easily, abdominal pain, dizziness and nausea. The prevalence for headache ranged from 74.2% among the youngest women to 35.4% among the oldest women in our study. It is known that headache prevalence decreases after 50 years of age , both for migraine and other types of headache .
A decrease in the prevalence of backache from 55.2% to 39.6% with age was seen in this study. Low back pain mostly occurs in an individual's most productive years, with a peak in the age interval 35–59 years [30–32], which is in line with the results presented. Abdominal pain and nausea decreased with age as well. These two symptoms were less common at the older end of the age range than at the younger end. In a recent UK primary care study the incidence of abdominal pain in women was seen to decrease between the ages of 35 and 60, where after which a slight increase could be seen .
The findings from the present study may be useful for public health administrators in forming health policies. They may also be used in a clinical setting where doctors are giving advice to their patients. Since the major part of the symptoms become less prevalent with age, other strategies than pharmacological treatment may come into perspective.