Shortness of breath at night and health status in congestive heart failure: effects of environmental conditions and health-related and dietary factors.

OBJECTIVES: Recent studies suggest that persons with congestive heart failure (CHF) may be at higher risk for the short-term effects of air pollution. We carried out this daily diary panel study in Montreal, Quebec, to determine whether indicators of self-reported health status and shortness of breath at night were associated with selected health-related and dietary factors, weather conditions, and air pollution.
METHODS: Thirty-one subjects with CHF participated in this study in 2002 and 2003. Over a 2-month period, they measured their oxygen saturation, pulse rate, weight, and temperature each morning and recorded these and other data in a daily diary. Every morning they recorded on visual analogue scales their assessments of their general health, shortness of breath, and weakness, their weight, temperature and other data in a daily diary. Air pollution and weather conditions were obtained from fixed-site monitoring stations. This paper deals only with the daily self-reported health outcomes of general health and shortness of breath. We made use of mixed regression models, adjusting for within-subject serial correlation and temporal trends, to determine the association between oxygen saturation and pulse rate and health-related, dietary and environmental variables. Depending on the model, we accounted for the effects of a variety of health-related and dietary variables as well as NO(2), ozone, maximum temperature and change in barometric pressure at 8:00AM from the previous day.
RESULTS: Of the many associations for self-reported general health and shortness of breath, we found only a few statistically significant predictors, although increases in many variables showed decrements in self-reported general health and shortness of breath. The statistically significant associations with general health were increases in daily pulse rate and body weight, higher maximum ambient air temperature, higher relative humidity, and ozone (on the concurrent day). Statistically significant predictors of worsened shortness of breath at night were increases in blood pressure, body weight, and higher maximum ambient air temperature (lag 0 and 1 days). We also found that there was little confounding between environmental variables and health and dietary factors.
CONCLUSIONS: The findings from the present investigation suggest that certain health-related indices and environmental conditions affect self-reported health and shortness of breath in CHF patients, although larger studies are needed to confirm these findings.