Continued exercise for 10 years linked to reduced risk type 2 diabetes

15th February 2023

Continued moderate or vigorous exercise over a 10-year period is associated with a significantly reduced risk of incident type 2 diabetes

Participants who continued to exercise for up to 10 years following completion of a 12 month randomised trial, had a significantly lower risk of developing incident type 2 diabetes according to the findings of a study by Chinese researchers.

Globally, type 2 diabetes affects around 462 million people or just over 6% of the entire population. Lifestyle modifications such as diet or increased exercise are known to reduce the risk of developing the disease. However, most of the available evidence for effects of lifestyle modification has been derived from high-risk individuals, for instance, those with elevated fasting glucose levels, or those who are both overweight and having impaired glucose tolerance. A further problem is that many of these intervention studies were of a relatively short duration. It is therefore less unclear whether maintenance of lifestyle modifications such as increased physical activity, over the longer term, still reduces the risk of developing T2D.

In the current study, Chinese researchers reported the longer term outcomes of a 12 month randomised trial they had undertaken. In the original trial, participants with non-alcoholic fatty liver disease, were randomised to vigorous to moderate physical activity, moderate exercise (brisk walking) or no exercise for 12 months. The results of the trial showed that both forms of exercise were effective at reducing intrahepatic triglyceride levels compared to those who did not exercise.

Following the trial, the majority of the study participants were followed-up after 2 and 10 years to assess the incidence of T2D, defined as a fasting plasma glucose of 6.9 mmol/L and a HBA1c of > 6.5% and or the use of anti-diabetic treatment.

Continued exercise and incident type 2 diabetes

From an original cohort of 208 participants who completed the year long trial, 195 and 179 remained for subsequent assessment after 2 and 10 years respectively.

The cumulative incidence of T2D was 2.1 per 100 person-years, 1.9 and 4.1 in those who continued with vigorous, moderate or no exercise respectively. In fact, the risk of T2D was reduced by 49% among those performing vigorous exercise (relative risk, RR = 0.51, 95% CI 0.27 – 0.94, p = 0.01) and by 53% among moderate level intensity exercise (RR = 0.47, 95% CI 0.25 – 0.89, p = 0.01) compared to the non-exercising group.

While both exercise groups had significant reductions in HBA1c levels compared to non-exercisers during the follow-up period, fasting plasma glucose levels while numerically lower in the two exercising groups than the non-exercise control group, these differences were non-significant.

The authors suggested that vigorous to moderate aerobic physical activity could be used to prevent T2D, particularly in those with obesity.

Citation
Chen Y et al. Effect of Moderate and Vigorous Aerobic Exercise on Incident Diabetes in Adults With Obesity: A 10-Year Follow-up of a Randomized Clinical Trial. JAMA Intern Med 2023

Weight-lifting and cardiovascular disease mortality

10th October 2022

Weight-lifting may reduce cardiovascular mortality risk but the dose-response relationship and the combined benefit with aerobics is unclear

Both aerobic physical activity and muscle-strengthening activities on 2 or more days a week such as weight-lifting, are recommended to provide substantial health benefits. In fact, there is good evidence that increased levels of physical activity via aerobic type activities, are associated with a lower mortality risk. However, far less is known about the all-cause and cardiovascular mortality benefits of strength training activities. One analysis of prospective studies found that participation in strength training activities (compared to none) was associated with 21% lower risk of all-cause mortality and a borderline association with lower cardiovascular mortality. Moreover, the authors also noted in the paper that there was lack of evidence on the dose-response relationship between muscle-strengthening activities and cardiovascular risk.

For the present study, a team of US researchers set out to examine the relationship between weight-lifting and all-cause, cardiovascular and cancer mortality both independently and when combined with aerobic moderate to vigorous physical activity (MVPA). They used data from the Prostate, Lung, Colorectal and Ovarian (PLCO) screening trial which began in 1993 and 13 years later, sent follow-up questionnaires to participants which asked about levels of weight-lifting as well as both moderate and vigorous physical activity. For the subsequent analysis of mortality data, the team adjusted for demographic and lifestyle factors which had been assessed in the follow-up questionnaire. In addition, researchers considered the mortality impact based on individual’s reported levels of aerobic MVPA, which was categorised as none, some, meets or exceeds.

Weight-lifting and cardiovascular mortality

A total of 99,713 individuals with a mean age at the start of the follow-up period of 71.3 years (52.6% female) were included in the analysis and followed over an average of 9.6 years. Overall, 23% of participants reported undertaking any weight-lifting activities.

Adults reporting any level of weight-lifting activity had a 9% lower risk of all-cause mortality (Hazard ratio, HR = 0.91, 95% CI 0.88 – 0.94) and for cardiovascular disease mortality (HR = 0.91, 95% CI 0.86 – 0.97) but the reduction in cancer mortality risk was non-significant. Without any adjustment for aerobic activity, lifting weights 1 – 2 times/week was independently associated with a 17% reduced risk of cardiovascular mortality (HR = 0.73, 95% CI 0.79 – 0.97). Interestingly however, increasing the weight-lifting frequency to between 3 and 7 or more times/week did not further reduce the risk of cardiovascular mortality (HR = 0.76, 95% CI 0.71 – 0.82).

When researchers examined all-cause mortality based on the different MVPA categories, those undertaking weight-lifting 1 – 2 times/week and who met MVPA requirement, had 41% lower all-cause mortality (HR = 0.59, 95% CI 0.54 – 0.64). As before, among those who ‘met’ the MVPA requirements, higher levels of weight-lifting activity, did not further reduce all-cause mortality (HR = 0.61).

The authors concluded that both weight-lifting and aerobic activity were independently associated with a reduced all-cause and cardiovascular disease mortality risk and support the notion that both activities were associated with longevity in older adults.

Citation
Gorzelitz J et al. Independent and joint associations of weightlifting and aerobic activity with all-cause, cardiovascular disease and cancer mortality in the Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial Br J Sports Med 2022

Study provides insight into how aerobic exercise might reduce colon cancer cell proliferation

13th April 2022

Aerobic exercise induces interleukin-6 and suppresses a marker of DNA damage, offering insight as to how it could reduce the risk of colon cancer

Aerobic exercise increases expression of interleukin-6 (IL-6) and suppresses the level of γ-H2AX, a marker for DNA damage, in a colon cancer cell line, providing a possible explanation as to how exercise reduces the risk of colon cancer. This was the conclusion of a study by a team from the School of Biomedical, Nutritional and Sport Sciences, Newcastle University, Newcastle upon Tyne, UK.

In 2020, globally, colon cancer was responsible for over 1.9 million cases and 0.9 million deaths. Moreover, there is evidence that physical activity reduces cancer risk and in 2018, the American physical activity guidelines advisory committee concluded that there is now strong evidence that physical activity lowers the risk of seven types of cancer (namely colon, breast, kidney, endometrium, bladder, and stomach cancer, and oesophageal adenocarcinoma) although this evidence is derived from epidemiological studies.

Aerobic exercise is a form of physical activity and an accumulating body of evidence suggests that the incubation of cancer cells with post-exercise serum can have powerful effects on key hallmarks of cancer cell behaviour in vitro. I

n fact, a 2020 systematic review concluded that the transient serological responses to acute exercises reduce cancer cell growth, although many questions remain regarding the underlying mechanistic pathways and potential effect modifiers.

Nevertheless, while the evidence suggests a beneficial effect on cancer risk, in order to achieve a better understanding of how aerobic exercise affects the biological processes involved in cancer, requires comparison with a control group.

For the present study, the UK team recruited men with lifestyle risk factors for colon cancer e.g., older than 50 years of age, with a body mass index (BMI) > than 25 or a waist circumference > 94 cm and who did not engage in > 30 minutes of moderate physical activity at least 3 days/week over the previous 3 months.

The same participants served as their own control and undertook aerobic activity (6 x 5 minutes of cycling) and a control intervention (60 minutes of a quiet rested sitting), which was separated by a period of 2 to 7 days.

The team used LoVo cells, which served as a model of colon cancer and the primary outcome of the study was the mean difference in LoVo cell proliferation between exercise and control conditions. A total of 7 cytokines were quantified including interleukins (IL-) 6, 8 and 10 as well as markers of DNA damage such as γ-H2AX, were assessed.

Aerobic exercise and LoVo cell response

A total of 16 men with a mean age of 60 years and mean BMI of 29.9 were included in the study.

After stimulation of the LoVo cells with post-exercise serum, there was a decrease in cell proliferation compared to pre-exercise serum (-4.2%, 95% CI -6.8 to -1.5%, p = 0.006). In contrast, during the control period, there was a post-control increase in cell proliferation compared to pre-control serum (5.4%, 95% CI 2.2 to 8.6%, p = 0.003).

After adjustment for pre-values, the authors calculated that exercise-conditioned serum reduced cell proliferation compared to control by 5.7% (95% CI -8.8 to -2.6%, p = 0.002).

Turning to changes in biological markers, the researchers found that exercise reduced levels of γ-H2AX by 24% (p = 0.029) which reflected a decrease in DNA damage. In addition, the acute bout of aerobic exercise only significantly increased expression of one marker, IL-6, by 24.6% (p = 0.002).

The authors concluded the increased IL-6 expression may help explain the observed benefits of aerobic exercise in epidemiological studies and could account for why exercise helps to reduce colon cancer risk.

Citation
Orange ST et al. Acute aerobic exercise‐conditioned serum reduces colon cancer cell proliferation in vitro through interleukin‐6‐induced regulation of DNA damage Int J Cancer 2022