Comparison of participants and non-participants in a population study of injuries. The study of men born in 1913 and 1923

Survey nonresponders to a medication-beliefs survey have worse adherence and persistence to chronic medications compared with survey responders

OBJECTIVE

The primary objective of this study was to investigate whether nonresponders to a medication-beliefs survey exhibited different adherence and persistence patterns than survey responders.

METHODS

A medication-beliefs survey was mailed to 7795 adults aged from 40 to 88 years, who filled a qualifying index prescription (cardiovascular, dyslipidemia, oral-antihyperglycemic, oral-bisphosphonate, and asthma-controller medications) in June 2008 at 1 national and 2 regional retail pharmacies. Adherence and persistence to the index drug class was measured using pharmacy-claims data over 12 months. A multivariate generalized linear model with a negative binomial distribution and log-link function was used to determine whether response status was a significant predictor of adherence. Kaplan-Meier estimates of survival curves were used to assess the time to discontinuation (persistence). Differences between nonresponders and responders were assessed using the log-rank test.

RESULTS

The survey response rate was 24.25%. The final analytic sample size after exclusions was 6740 patients (5044 nonresponders and 1696 responders). On the basis of multivariate generalized linear model analysis, survey nonresponders had 11% lower medication adherence compared with responders (P < 0.01; goodness-of-fit=1.09 as defined by deviance/df statistics). The proportion of nonresponders deemed nonpersistent at day 305 was 66.3% compared with 58.1% of responders (P < 0.001). The Kaplan-Meier persistence curves were significantly different for nonresponders and responders as assessed by the log-rank test (χ statistic=49.38; P < 0.001).

CONCLUSIONS

Our study found that the responders and nonresponders to a medication-beliefs survey differed significantly in their subsequent adherence and persistence, suggesting that biased survey results are likely to accompany low response rates in surveys of medication use. The use of modest monetary incentives had a small effect on survey response; multiple survey levers are recommended to reduce nonresponse and the potential for biased results.

Marital status, educational level and household income explain part of the excess mortality of survey non-respondents

Survey respondents and non-respondents differ in their demographic and socio-economic position. Many of the health behaviours are also known to be associated with socio-economic differences. We aimed to investigate how much of the excess mortality of survey non-respondents can be explained by the socio-economic differences between respondents and non-respondents. Questionnaire-based adult health behaviour surveys have been conducted in Finland annually since 1978. Data from the 1978 to 2002 surveys, including non-respondents, were linked with mortality data from the Finnish National Cause of Death statistics and with demographic and socio-economic register data (marital status, education and household income) obtained from Statistics Finland. The mortality follow-up lasted until 2006, in which period there were 12,762 deaths (7,994 in men and 4,768 in women) during the follow-up. Total and cause-specific mortality were higher among non-respondents in both men and women. Adjusting results for marital status, educational level and average household income decreased the excess total and cause-specific mortality of non-respondents in both men and women. Of the total excess mortality of non-respondents, 41% in men and 20% in women can be accounted for demographic and socio-economic factors. A part of the excess mortality among non-respondents can be accounted for their demographic and socio-economic characteristics. Based on these results we can assume that non-respondents tend to have more severe health problems, acute illnesses and unhealthy behaviours, such as smoking and excess alcohol use. These can be reasons for persons not taking part in population surveys.

Non-response to baseline, non-response to follow-up and mortality in the Whitehall II cohort

BACKGROUND

Little is known about the associations between non-response to follow-up surveys and mortality, or differences in these associations by socioeconomic position in studies with repeat data collections.

METHODS

The Whitehall II study of socioeconomic inequalities in health provided response status from five data collection surveys; Phase 1 (1985-88, n = 10 308), Phase 5 (1997-99, n = 6533), and all-cause mortality to 2006. Odd-numbered phases included a medical examination in addition to a questionnaire.

RESULTS

Non-response to baseline and to follow-up phases that included a medical examination was associated with a doubling of the mortality hazard in analyses adjusted for age and sex. Compared with complete responders, responders who missed one or more phases, but completed the last possible phase before they died, had a 38% excess risk of mortality. However, those who missed one or more phases including the last possible phase before death had an excess risk of 127%. There was no evidence that these associations differed by socioeconomic position.

CONCLUSION

In studies with repeat data collections, non-response to follow-up is associated with the same doubling of the mortality risk as non-response to baseline; an association that is not modified by socioeconomic position.

Non-response and related factors in a nation-wide health survey

OBJECTIVE

To analyse selective factors associated with an unexpectedly low response rate.

SUBJECTS AND METHODS

The baseline questionnaire survey of a large prospective follow-up study on the psychosocial health of the Finnish working-aged randomly chosen population resulted in 21,101 responses (40.0%) in 1998. The non-respondent analysis used demographic and health-related population characteristics from the official statistics and behavioural, physical and mental health-related outcome differences between early and late respondents to predict possible non-response bias. Reasons for non-response, indicated by missing responses of late respondents, and factors affecting the giving of consent were also analysed.

RESULTS

The probability of not responding was greater for men, older age groups, those with less education, divorced and widowed respondents, and respondents on disability pension. The physical health-related differences between the respondents and the general population were small and could be explained by differences in definitions. The late respondents smoked and used more psychopharmaceutical drugs than the early ones, suggesting similar features in non-respondents. The sensitive issues had a small effect on the response rate. The consent to use a medical register-based follow-up was obtained from 94.5% of the early and 90.9% of the late respondents (odds ratio: 1.70; 95% confidence interval: 1.49-1.93). Consent was more likely among respondents reporting current smoking, heavy alcohol use, panic disorder or use of tranquillisers.

CONCLUSIONS

The main reasons for non-response may be the predisposing sociodemographic and behavioural factors, the length and sensitive nature of the questionnaire to some extent, and a suspicion of written consent and a connection being made between the individual and the registers mentioned on the consent form.

Sleep complaints predict coronary artery disease mortality in males: a 12-year follow-up study of a middle-aged Swedish population

OBJECTIVES

Only a few prospective surveys have been performed to investigate the relationship between sleep complaints and coronary artery disease (CAD) mortality. This study was conducted to determine whether sleep complaints in a middle-aged population predicted total mortality and CAD mortality.

DESIGN

A population-based prospective study. Setting. The County of Dalarna, Sweden.

SUBJECTS AND METHODS

In 1983, a random sample of 1870 subjects aged 45-65 years responded to a postal questionnaire (response rate 70.2%) including questions about sleep complaints and various diseases. Mortality data for the period 1983-95 were collected, and Cox proportional hazard analyses were used to examine the mortality risks.

RESULTS

At 12-year follow-up 165 males (18.2%) and 101 females (10.5%) had died. After adjustment for a wide range of important putative risk factors, difficulties initiating sleep (DIS) were related to CAD death in males [relative risk (RR), 3.1; 95% confidence interval (CI), 1.5-6.3; P < 0.01], but not in females. Short or long sleep duration did not influence risk of CAD mortality or total mortality for either gender. Depression in males increased the risk of death attributed to CAD (RR, 3.0; 95% CI, 1.1-8.4; P < 0.05) and total mortality (RR, 2.2; 95% CI, 1.1-4.5; P < 0.05).

CONCLUSION

These results provide evidence that there is an association between difficulties falling asleep and CAD mortality in males.

Increased mortality among sleepy snorers: a prospective population based study

BACKGROUND

The long term health consequences of snoring and sleep apnoea syndrome are still uncertain. This study was conducted to assess the mortality risk associated with snoring and excessive daytime sleepiness (EDS), the two main symptoms of sleep apnoea syndrome, in men.

METHODS

In 1984 a sample of 3100 men aged 30-69 responded to a postal questionnaire including questions about snoring, EDS, and the prevalence of various diseases (response rate 77.1%). Mortality data for the period 1985-1995 were collected for the complete sample.

RESULTS

During the 10 year follow up period 213 men died, 88 of cardiovascular diseases. Compared with subjects with no snoring or EDS in 1984, men with isolated snoring or EDS displayed no significantly increased mortality. The combination of snoring and EDS was associated with a significant increase in mortality. However, the relative rates decreased with increasing age, and in men aged 60 and above no effect on mortality was found. Men below the age of 60 with both snoring and EDS had an age adjusted total death rate which was 2.7 times higher than men with no snoring or EDS (95% CI 1.6 to 4.5). The corresponding age adjusted hazard ratio for cardiovascular mortality was 2.9 (95% CI 1.3 to 6.7) for subjects with both snoring and EDS. Further adjustment for body mass index and reported hypertension, cardiac disease, and diabetes reduced the relative mortality risk associated with the combination of snoring and EDS to 2.2 (95% CI 1.3 to 3.8) and the relative risk of cardiovascular mortality to 2.0 (95% CI 0.8 to 4.7).

CONCLUSION

Snoring without EDS does not appear to carry an increased risk of mortality. The combination of snoring and EDS appears to be associated with an increased mortality rate, but the effects seems to be age dependent. The increased mortality is partly explained by an association between "snoring and EDS" and cardiovascular disease.

Reproducibility and validity of a postal questionnaire. The abdominal symptom study

OBJECTIVE

To find out whether it is possible to examine abdominal/gastrointestinal symptoms by a postal questionnaire.

DESIGN

In the Abdominal Symptom Study a postal questionnaire was sent to a representative sample of adults (n = 1290) on two occasions, one year apart. The questionnaire was sent a third time to a subsample (n = 110), and to another sample (n = 213) who had not seen the questionnaire before. A subsample (n = 150 of the 1290) was subjected to a medical interview and examination.

SETTING

The municipality of Osthammar, Sweden.

PARTICIPANTS

A sample (9.3%) of all Swedish citizens (20-79 yrs) in the municipality.

MAIN OUTCOME MEASURE

Reproducibility and validity of a postal questionnaire.

RESULTS

The response rate was 90%. Roughly 50% of the study population reported abdominal symptoms. The reproducibility of the results was satisfactory, as was the validity of the questionnaire evaluated by medical interview and examination. Non-responders did not report more symptoms than responders.

CONCLUSION

It is possible to examine abdominal/gastrointestinal symptoms with a postal questionnaire. The questionnaire used in The Abdominal Symptom Study seems to be useful for this purpose.

The population study of women in Gothenburg 1980-81--the third phase of a longitudinal study. Comparison between participants and non-participants

A representative population sample comprising 1,462 women was studied in Gothenburg, Sweden in 1968-69, and a third follow-up study was carried out in 1980-81. The participation rates in the baseline study and during the follow-up studies were high. In 1980-81 women in two new age strata, aged 26 and 38, were added. Women who had moved to or from Gothenburg during the study period were not found to differ from those who were living in Gothenburg during the total study period, while there were a few differences of statistical significance between refusers and participants in 1980-81. The mortality among initial refusers was about doubled compared to that of those who participated in the baseline study.

Long-term effects of head injuries sustained during life in three male populations

Data on defined head injuries, suffered during life, were related to possible long-term sequelae among 1112 men aged 30, 50, or 60 years who were sampled from the general population of Gothenburg, Sweden. There was a significant relationship between closed-head injury associated with reported impaired consciousness and occurrence of symptoms of the postconcussional type, self-assessed health variables, and the performance of finger-tapping and reaction-time tests. There was a cumulative effect of repeated head injuries: the more head injuries that were suffered, the more symptoms and more inferior performance were noted. Age at the time of the accident did not influence the occurrence of reported sequelae. Alcohol intake and smoking were powerful factors confounding the postinjury picture, but after taking these factors into account the results were generally the same. The study indicates that head injuries with impaired consciousness, no matter how short, are capable of causing permanent sequelae.

Age-related changes in blood pressure

This report is based on three different representative population samples of a total of 1304 men (50-79 years old) and 1246 women (38-79 years old) observed for up to 12 years. Subjects' consumption of antihypertensive drugs and blood pressure levels in subjects with and without such treatment are presented. The prevalence of treatment with antihypertensive drugs (including beta-blockers and diuretics for other indications) increased from 2% at age 50 years to 37% at 79 years of age among the men and from 1% at 38 years to 61% at 79 years of age among the women. The mean systolic/diastolic blood pressure in untreated subjects increased from 138/91 mm Hg at age 50 years to 159/91 mm Hg at age 70 years in the men and from 123/79 mm Hg at age 38 years to 168/93 mm Hg at age 70 years in the women. At age 79 years the mean systolic/diastolic blood pressure was 155/83 mm Hg in the men and 161/85 mm Hg in the women. In a longitudinal follow-up of reexamined subjects, there was an increase in systolic blood pressure levels up to age 75 years and a reduction in diastolic blood pressure after age 75 years in both sexes.

Head injuries in a population study

In a population study of altogether 1,112: 60-, 50-, and 30-year-old men performed in Göteborg, Sweden, data on head injuries suffered during life were obtained by personal interview. Two head injury concepts were used, one wide definition to cover all sorts of head injuries (HI-w) and one restricted only to delineate head injuries with evidence of presumed brain involvement (HI-r). 24% of the 60-year-old men, 21% of the 50-year-old men and 23% of the 30-year-old men reported at least one head injury with unconsciousness. When taking only the 3 first decades of life into account a significantly higher proportion of men in the youngest cohort had been unconscious than in the older ones, and the youngest men also had a significantly higher incidence of both HI-w and HI-r than the older men. Accidents at home, in roads and in sports/recreational areas dominated in childhood, place of work in adult age. HI-r accidents occurred somewhat more often in roads and sports/recreational areas than HI-w accidents. Falls, traffic and blows/impacts were the most common causes. Falls dominated in childhood. Motor vehicles were more often involved in childhood accidents in the youngest cohort than in the two older ones. The proportion of self-care decreased due to a strong secular trend. Out-patient care increased due to both a secular trend and to the age of the victim. The proportion of in-patient care increased with the age of the victim but showed no evident secular trend. 1/5 to 1/3 of all head injuries with unconsciousness were not medically attended.