Die verband tussen die fisieke-aktiwiteitsindeks en rook op die lipiedbeeld by mans (35-64 jaar) in 'n Suid-Afrikaanse stedelike gemeenskap

Abstract

The physical activity index and smoking and the lipid profile of men (35-64 years) in a South African urban community 1. Problem and purpose of this research The modern lifestyle, including cigarette smoking and physical inactivity, is among the multiple contributors to the development of atherosclerosis and increased risk of coronary heart disease (CHO) (Leon, 1991 :46). Increasing total-cholesterol levels correlate with an increased risk of developing coronary heart disease. Coronary mortality has also been shown to vary inversely with high-density lipoprotein cholesterol (HDL-C) levels (Waters, 1994: 1 ). Regular participation in aerobic-type activity increases high-density lipoprotein cholesterol (including apolipoprotein A) and is associated with a decrease in low-density lipoprotein cholesterol and TC/HDL-ratio (Wood & Stefanick, 1990:414-417). Indirectly, smoking enhances atherogenesis by reducing high-density lipoprotein cholesterol and increasing low-density lipoprotein cholesterol (Leon, 1995 :136). The aim of this study was to investigate the relationship of leisure-time physical activity (LTPA) with some selected blood lipids according to different age groups, as well as the influence of cigarette smoking on the above-mentioned relationships. 2. Method of research This study forms part of a community study of two SA cities, Vanderbijlpark and Witbank. Data were obtained from a stratified-systematic sample of 536 white male residents of the two industrialized communities (Witbank and Vanderbijlpark) between the ages of 35 and 64 years. The two age groupings in this study were as follows: 35-49 and 50-64 years. Before participating

in any form of physical assessment a comprehensive medical/physical history and lifestyle questionnaire and an informed consent form was completed. The participants were subjected to a battery of tests, which included measurements of serum blood lipids, lipoproteins and apolipoproteins (apo Band apo A), body mass index and PWC170. Each subject was allocated to one of three LTPA categories (low, moderate and high). A one-way analysis of variance was used to ascertain any differences among the three levels of LTP A with respect to the dependent variables. No statistically significant differences regarding body mass were present between the low-, moderate- or high-active men, as well as between the active and inactive men in both age groups. Post hoc comparisons were done according to Tukey' s test. Practical significance was determined by means of effect size calculations (ES) (Thomas et al., 1991 :347). The active and inactive men were also subdivided into smokers and non-smokers according to both age groups (3 5-49 and 50-64 years) in order to investigate the possible influence of smoking on the influence of PA on selected blood lipids. Two-tailed t-tests were applied to determine the statistically significantly differences between the means of the respective groups (Thomas & Nelson, 1996: 148). Practical significance was determined by means of effect size, in instances where intergroup differences were statistically significant (p≤0.05) (Thomas et al., 1991 :347). The measurements were done in the following manner: Body mass index (BMI)(kg.nl). This was calculated by dividing body mass (kg) by height (m2 ) (Malina, 1995 :209; Pollock et al., 1995 :168). Serum blood lipids. Non-fasting blood samples were taken. Laboratory analyses consisted of total cholesterol concentration (TC), low-density lipoprotein (LDL-C), high-density lipoprotein (HDL-C) and apolipoproteins (apo Al and apo B), as described by Vermaak et al. (1991 :368). Leisure-time physical activity index (LTPA index). The physical activity index suggested by Sharkey (1990:8; 1997:8) was used. In this regard, a physical activity index of 48 implies for example that a particular person who took part in leisure-time physical activity consisting oflonger than 3 0 minutes (duration= 4) of aerobic-type activities, three times per week

(frequency = 4), experienced it as moderately heavy (intensity= 3). The LTPA index was based on a person's regular daily activity by multiplying each person's score for each category (score= intensity x duration x frequency) (Sharkey, 1990:8; 1997:8). 3. Results The following results were found: 3.1 The average LTPA index (both age groups) can be regarded as low (L TPA = ~ 16). The highest average LTP A index of 14. 67 was present in the 3 5-49 years age group with the lowest average LTPA index of9.93 in the 50-64 years age group. 3.2 The younger high-active men (35-49 years) showed a statistically significantly higher (favourable) HDL-C compared to the moderate- and low-active men in the same age group. The difference between the high-active and moderate-active men was also practically significant. 3.3 The moderate-active men showed a significantly and practically significantly higher HDLC in the 50-64 years men, compared to the moderate-active men (35-49 years). 3.4 The high-active men (35-49 years) showed a significantly and practically significantly lower TC/HDL-ratio compared to the moderate-active men (35-49 years). 3.5 It seems that an increase in physical activity could not evoke any statistically significant differences concerning TC, LDL-C, apo B and apo Al in both age groups (3 5-49; 50-64 years). 3.6 The active smokers (35-49 years) showed a statistically and practically significantly lower HDL-C when compared to the active non-smokers (35-49 years). It seems that some possible deleterious effects of smoking have a neutralising effect on the positive influence of an increased level of physical activity in the active smokers (35-49 years). It seems that

smoking had a depressing effect on HDL-C in the younger men (35-49 years). 3. 7 The active non-smokers (3 5-49 years) showed a statistically significantly higher HDL-C when compared to the inactive non-smokers (35-49 years). It seems that an increased activity level may render protection against coronary heart disease (CHD) due to the significantly higher (favourable) HDL-C in the active men (35-49 years) compared to the inactive men in the same age group. This was not true for the men in the 50-64 years group, although the trend was similar to that of the younger men (35-49 years). 3.8 Smoking exerted no statistically significantly influences on TC, LDL-C and apo B in active and inactive men of both age groups (35-49 and 50-64 years). 3.9 The active non-smokers (35-49 and 50-64 years) showed a statistically significantly lower TC/HDL-ratio compared to the inactive non-smokers (35-49 and 50-64 years). It seems that an increased activity level has a favourable influence on TC/HDL-ratio as indicated in the active non-smokers of both age groups. 3.10 The active non-smokers (35-49 years) showed a statistically significantly higher apolipoprotein A compared to the inactive non-smokers (35-49 years). It seems that an increased activity level has a favourable influence on apo A as indicated in the active nonsmokers of the younger age group (35 -49 years). This was not true for the older age group (50-64 years), although the trend was similar to that of the younger men (35-49 years).